| Glass Glossary |
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| [ A ] |
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Abbe value
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(Property) The reciprocal dispersive power, a value used in optical design, expressed mathematically as: Abbe value = (nd - 1)/(nF - nC), where nd, nF and nC are the refractive indices for the helium line at 587.6 nm, and for the hydrogen line at 486.1 and 656.3 nm, respectively.
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Abraded Strength
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(Property) Breaking stress of glass measured after a processing of controlled abrasion. This is used to determine the strength for practical use.
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AC Volume Resistivity E and ro
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(Property) See eArrhenius equationf. The AC volume resistivity r is expressed by the equation, r = roexp(E/RT).
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Additivity Relationship
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(Property) Many glass properties (P) obey the following linear relationship.
P = p1a1 + p2a2..+ pnan,
where pi is the additivity factor for the i'th component, and ai is the content of the i'th component in mass%, mol% mass fraction or mol fraction. Note that a1 + a2..+an = 100 % or 1.
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Anisotropic
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(Shape,Feature&Manufacturing Process) A glass which dose not exhibit the same properties in all directions with reference to light, thereby resulting in more than one refractive index.
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Annealing
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(Property) A controlled cooling process for glass, designed to reduce the thermal residual stress to a commercially acceptable level, and, in some cases, to modify the structure.
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Annealing Point
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(Property) At this temperature, the internal stresses of glass are substantially released in a matter of minutes. The viscosity corresponding to this temperature is 1013 to 1013.5 dPa.s and is dependent on the measurement method.
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Annealing Range
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(Property) The range of glass temperature in which stress in glass can be released at a commercially practical rate. For purposes of comparing glasses, the annealing range is assumed to correspond with the temperature between the annealing point and the strain point.
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Arrhenius Equation
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(Property) The temperature dependence of the diffusion coefficient or the electrical conductivity, k, is expressed by the equation, k = Aexp(
|E/RT), where A, E, R and T are a constant, an activation energy, the gas constant and the absolute
temperature, respectively |
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| [ B ] |
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Balloon
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(Shape,Feature&Manufacturing Process) A small spherical hollow glass.
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Bead
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(Shape,Feature&Manufacturing Process) A small spherical grain of glass.
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| [ C ] |
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Casting
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(Shape,Feature&Manufacturing Process) The process of shaping glass by pouring the molten material into or onto molds, tables or rolls.
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Cellular Glass
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(Shape,Feature&Manufacturing Process) A thermally insulating material consisting of a high volume fraction of gaseous inclusions distributed throughout a glass matrix.
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Chemical Durability
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(Property) The lasting quality (both physical and chemical) of a glass surface. It is frequently evaluated after prolonged contact with water, chemicals or atmosphere in terms of chemical and physical changes in the glass surface, or in terms of changes in the contents of a vessel.
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Climate Resistance
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(Property) Resistance of glass to weathering.
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Composite
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(State) Composite composed of glass and other materials.
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Crown Glass
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(1) Soda-lime glass. (2) A type of window glass shaped by whirling a large glass sphere to form a flat circular disk with a lump in the center formed by the glassblowerfs rod. (3) Abbreviation of optical crown glass.
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Crystal Glass
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A colorless, highly transparent glass used for art and tableware.
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Crystallization Temperature
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(Property) The temperature at which glass is heat-treated for crystallization, or the temperature detected by DTA at which a crystal begins to crystallize.
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CVD
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(Shape,Feature&Manufacturing Process) Abbreviation for chemical vapor deposition. A preparation process of coatings on a substrate by the pyrolitic deposition of a gas phase.
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| [ D ] |
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DC Volume Resistivity E and ro
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(Property) See eArrhenius equationf. The electrical resistivity r is expressed by the equation, r = roexp(E/RT).
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Deformation Point
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(Property) The temperature at the maximum peak of the thermal expansion curve of glass. This temperature depends on the measurement method of thermal expansion.
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Diffusion Coefficient Equation
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(Property) See Arrhenius equation. The diffusion coefficient D is expressed by the equation, D = Doexp(
|E/RT).
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Dilatometric Softening Point
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(Property) See edeformation temperaturef.
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Dispersion
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(Property) Variation of refractive index with optical wavelength.
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Dispersion Formula
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(Property) The equation that expresses the dependence of the refractive index on the optical wavelength, n2 =A0 + A1L2 + A2L-2 + A3L-4 +A4L-6 + A5L-8, where n and L are the refractive index and optical wavelength respectively, and A0 , A1, A2, A3, A4, and A5 are constants.
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Dissipation Factor
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The same meaning with eloss tangentf.
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Doped(Stuffed)
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(Shape,Feature&Manufacturing Process) A material doped some components into porous glass from solution, or penetrated some components from the surface into the body by ion beams.
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Dynamic Fatigue
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(Property) Decrease of the breaking stress of glass with increased duration of load under cyclic loading conditions.
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| [ E ] |
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Electric Conductivity, E and So
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(Property) See Arrhenius equation. The electrical conductivity S is expressed by the equation, S = Soexp(
|E/RT).
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Erasable
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(Usage) A memory media capable of memory erasure.
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Expansion Coefficient
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(Property) The tangent of the linear thermal expansion curve at a specified temperature, or the tangent of the linear thermal expansion between two specified temperatures.
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| [ F ] |
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Fiber Array
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(Usage) An optical device made by fusing a number of optical fibers followed by polishing. Image propagation is enable using this device.
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Flat Glass
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(Shape,Feature&Manufacturing Process) A general term covering sheet glass, plate glass, float glass, and various forms of rolled glass.
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Flint Glass
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(1) A heavy, colorless, brilliant lead-bearing glass. (2) Abbreviation of optical flint glass. (3) A clear colorless soda lime glass used for bottle or tableware.
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Foam glass
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(Shape,Feature&Manufacturing Process) The same material with ecellular glassf.
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Frit
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(Shape,Feature&Manufacturing Process) A powder glass that has been melted and quenched in water or air, followed by grinding or milling. It is frequently used for printing ink, glazing or sealing.
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Fulcher Equation
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(Property) According to Fulchcr, the viscosity-temperature relationship is conveniently described by the following equation; log (viscosity) = A + B/(T - To) where T is temperature and A, B and To are constants. These constants can be determined using 3 viscosity data. However, the data in the annealing range should not be used.
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| [ G ] |
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Glass
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(State) An amorphous solid having a glass transition temperature. Ordinarily an inorganic product of fusion that has cooled to a rigid condition without crystallizing.
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Glass-Ceramics
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(State) Solid material, partly crystalline and partly glassy formed by the controlled crystallization of a glass.
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Glass Transition Temperature
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(Property) The temperature, Tg at which glass transforms from an elastic to a viscoelastic material on heating, characterized by the onset of a rapid change in some specific mechanical or thermal property. Observed Tg can vary significantly depending on the property chosen for observation and the experimental technique. Typical methods are dilatometry and DTA.
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Graded Index
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(Shape,Feature&Manufacturing Process) A glass having a refractive index distribution of a specified profile from surface to body.
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| [ H ] |
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Hard Glass
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(Shape,Feature&Manufacturing Process) 1) A glass of relatively high viscosity at elevated temperatures. 2) A glass with a high softening point. 3) Commonly refers to a glass that is difficult to melt.
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Hermetic Seal
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(Usage) A glass-sealed component which is completely gas-tight.
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| [ I ] |
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Internal Transmission
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(Property) Transmission of light in a glass body without consideration of surface reflection.
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Ion Electrode
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(Usage) A device for measurement of ion concentration having a thin separation membrane. A glass electrode for pH measurement is a typical device.
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Ion Exchange
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(Property) The phenomena by which ions in glass are replaced with other ions in surrounding medium (e.g. molten salt) outside of the glass. The major species relating to the exchange are monovalent positive ions such as alkali ions.
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Isolator
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(Usage) An optical component for a one-way optical path using polarizers.
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| [ J ] |
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| [ K ] |
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| [ L ] |
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Leached
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(Shape,Feature&Manufacturing Process) A residual glass dissolved soluble components from a glassy material by reaching with acidic solution.
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Lead Crystal Glass
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A heavy, highly transparent and brilliant silicate glass containing lead oxide more than 24 mass%. The glass is used for tableware, especially for cut glass.
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(Linear Thermal) Expansion Coefficient
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(Property) Tangent of linear thermal expansion curve at certain temperature.
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Liquidus Temperature
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(Property) The maximum temperature at which equilibrium exists between a molten substance, such as glass, and the primary crystalline phase.
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Littleton Point
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(Property) The same temperature with esoftening pointf.
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Loss Factor
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The same meaning with 'loss tangent'.
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Low Alkali
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(Shape,Feature&Manufacturing Process) A glass containing alkali oxide of less than 5 mass%.
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Low-melting
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(Shape,Feature&Manufacturing Process) Glass exhibiting viscous flow below at 600 C.
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| [ M ] |
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Machinability
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(Property) The ease with which a material can be machined by the process such as cutting or shaping.
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Machinable
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(Shape,Feature&Manufacturing Process) A glass that is easy to shape by machining, such as drilling or cutting.
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Main Dispersion
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(Property) The same meaning with emean dispersionf.
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Mean Dispersion F-C
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(Property) The refractive index difference from the F line (486.1 nm) to the C line (656.3 nm) of the spectrum, (nF
| nC).
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Melt
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(State) A high-temperature liquid of inorganic-material-related glass of which solidified body at low temperatures is not always glass.
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Meltability
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(Property) The easiness of melting a glass batch.
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Melting Point
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(Property) The range of furnace temperatures within which melting takes place at a commercially desirable rate, and at which the resulting glass generally has a viscosity of 101.5 to 102.5 dPa.s. For purposes of comparing glasses, it is assumed that glass of melting temperature has a viscosity of 102 dPa.s.(ISO 7884-1)
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Melting Temperature of Crystal
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(Property) The temperature detected by DTA at which a crystal begins to melt.
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Melting Temperature
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(Property) An arbitrarily defined reference point used for comparison purposes at which the glass viscosity is 100 dPa.s. (ASTM C162) The same temperature with emelting pointf.
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Mixed Alkali
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(Shape,Feature&Manufacturing Process) A glass containing multiple kinds of alkalis.
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Modified
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(State) A glassy material that is produced by the modification of glass by means of physical and/or chemical treatments.
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Molded
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(Shape,Feature&Manufacturing Process) Glass that is formed in a mold.
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Molded Lens
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(Usage) An optical glass lens formed in a mold without polishing.
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| [ N ] |
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Non-vitrified
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(State) A chemical composition with which a batch is experimentally verified not to form glass.
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Numerical Aperture
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(Property) A number, NA, related to the critical angle (a) of a cone of incident light to an optical fiber. When the refractive index of the core and the cladding of the fiber is ni and no , respectively, then NA = sin a =(2ni(ni - no))1/2.
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| [ O ] |
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Optical Absorbance
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(Property) The light intensity ratio, I/Io, where Io and I are intensity of the incident light and that of the transmitted light through a medium, respectively.
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Optical Absorption Edge
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(Property) In a continuous optical spectrum, the optical wavelength at a range longer than that at which optical absorption steeply decreases.
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Optical Crown Glass
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Any optical glass of low refractive index and low dispersion, having an Abbefs value of at least 55.0, or an Abbefs value between 50.0 and 55.0, and a refractive index grater than 1.60.
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Optical Density
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(Property) D = -log(I/Io), where Io and I are the intensity of the incident light and that of the transmitted light through a medium, respectively.
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Optical Flint Glass
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Any optical glass of high refractive index and high dispersion, having an Abbefs value of less than 50.0, or an Abbefs value between 50.0 to 55.0, and a refractive index less than 1.60.
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Optical Gap
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(Property) The photon energy, Eg, of Eg=hc/L where L is the wavelength of optical absorption edge, h is Plankfs constant and c is the light velocity.
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Optical Modulator
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(Usage) An optical device capable of light beam deflection.
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| [ P ] |
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Phase Separation
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(Property) The phenomena in which a melt separates into two liquids with different chemical composition.
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Photochromism
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(Shape,Feature&Manufacturing Process) A phenomena in which a material darkens up on exposure to light, but returns to its original color and original clearness under dark conditions.
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Phototropy
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(Shape,Feature&Manufacturing Process) The same phenomena with ephotochromismf.
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Plate Glass
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(Shape,Feature&Manufacturing Process) Flat glass formed by a rolling process, ground and polished on both sides, with essentially plane and parallel surfaces.
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Polarization-Maintaing Fiber
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(Usage) An optical fiber in which polarized light propagates in a specified direction.
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Porous Glass
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(Shape, Feature &Manufacturing Process) A glass filled with continuous micropore.
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PVD
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(Shape,Feature&Manufacturing Process) Abbreviation for physical vapor deposition. A preparation process of coatings on a substrate involving vacuum deposition and sputtering.
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| [ Q ] |
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| [ R ] |
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Radioactive Waste Solidification
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(Usage) A vitrification process in which radioactive components in radioactive waste are mixed with glass-forming constituents and the mixture is then melted to be made into glass form for disposal.
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Reflectance
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(Property) The ratio of reflected light to incident light, r. For perpendicular incident light, r=((n-l)/(n+l))2, where n is the refractive index of the glass.
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Relative Partial Dispersion
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(Property)
The Ratio of the dispersion for optical wavelength x and y to mean dispersion which is expressed as Px,y = (nx-ny)/(nF-nC), where nx, ny nF and nC are the refractive indices for the optical wavelength x, y, c and y. |
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| [ S ] |
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Sellmeier Formula
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(Property) The equation that expresses the dependence of the refractive index on the optical wavelength, n2 = 1 + A1L2/(L2 - B1) + A2L2/(L2- B2)+ A3L2/(L2-B3), where n and L are the refractive index and optical wavelength, respectively, and A1, A2, A3, B1, B2 and B3 are constants.
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Sheet Glass
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(Shape,Feature&Manufacturing Process) Flat glass made by continuous drawing.
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Sintered
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(Shape,Feature&Manufacturing Process) Glassware fabricated by fusing glass particles.
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Softening Point
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(Property) The temperature at which a glass fiber suspended in a furnace elongates at a specified rate under its own weight during heating. The viscosity at the softening point corresponds to a viscosity of 107.6 dPa.s which depends on the density and the surface tension of the glass.
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Soft Glass
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(1) A glass having a relatively low softening point or a high thermal expansion coefficient, or which is easy to melted. Typically soda- lime glass. (2)
A glass which is easily scratched or abraded.
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Sol-Gel
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(Shape,Feature&Manufacturing Process) A glass-making process involving the gelation of sol, followed by drying and sintering. A mixture of metal alcoxides, solvent and catalysis is typical starting material of sol.
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Standard Spectral Lines
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The characteristic narrow optical spectral lines used for the measurement of the optical constants of optical materials. The name, the optical wavelength, the light source and the color of each spectral line is shown in the following table.
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Notation
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t
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s
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r
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C
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C'
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D
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d
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Wavelength /nm
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1013.98
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852,11
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706.52
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656.27
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643.85
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589.24
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587.56
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Light source
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Hg v
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Cs v
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He v
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H
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Cd v
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Na v
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He
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Color
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IR
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IR
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red
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red
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red
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yellow
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yellow
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Notation
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e
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F
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F'
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g
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h
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i
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Wavelength /nm
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546.07
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486.13
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479.99
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435.83
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404.66
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365.01
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Light source
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Hg v
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H
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Cd v
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Hg v
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Hg v
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Hg v
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Color
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Green
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blue
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blue
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blue
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violet
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UV
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Static Fatigue
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(Property) The decrease in the breaking stress of glass with increased duration of load under conditions of static loading.
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Strain Point
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(Property) At this temperature, the internal stress of glass is substantially released in a matter of hours. The viscosity corresponding to this temperature is 1014.5 to 1015 dPa.s which is depend on measurement method.
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Strength of Glass
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(Property) Glass failure always results from a tensile component of stress. The breaking stresses of glass are far from uniform. They depend on the method of manufacturer and on the subsequent history, even if a glass with a fire-polished surface is very strong.
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Strengthened
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(Shape,Feature&Manufacturing Process) The same meaning with ftemperedf.
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Stress Optical Coefficient
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(Property) This coefficient is used for the determination of the internal stress of glass converted from the optical path difference measured by a photoelastic technique.
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Stress Relaxation
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(Property) The phenomena in which the stress in glass decreases with time due to the thermal effect.
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| [ T ] |
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Tangent Delta
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The same meaning with 'loss tangent'.
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Tempered
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(Shape,Feature&Manufacturing Process) A mechanically strong glass which is prestressed by physical or chemical treatments.
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Tg (DTA)
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(Property) The glass transition temperature measured by DTA or DSC(differential scanning calorimetry).
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Tg(Dilatometric)
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(Property) The glass transition temperature determined by means of the thermal expansion curve.
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Thin Film
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(State) A thin glassy coatings on substrate.
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Total Dispersion
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(Property) The same meaning with emean dispersionf.
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Transformation Point
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(Property)
The same meaning with eglass transition temperaturef.
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Transformation Temperature
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(Property) The same meaning with 'glass transition temperaturef.
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Transmittance
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(Property) The ratio of transmitted light energy to incident light energy, T. In the case of perpendicular incident light to a flat glass surface, T is expressed by the following formula, T=(1-R)2exp(-ax), where R is the reflectivity, a is the absorption coefficient, and x is the thickness of the flat glass, respectively.
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| [ U ] |
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| [ V ] |
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VFT Equation
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(Property) Abbreviation for Vogel-Fulcher-Tammann equation. The same equation with 'Fulcher equation'.
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| [ W ] |
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Wavelength Selector
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(Usage) An optical component of glass by which light of specified wavelength is chosen as transmitted light or reflected light.
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Weathering
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(Property) A phenomena in which the surface of glass deteriorates by the effect of the atmosphere, usually by the humidity.
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Working Point
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(Property) The temperature corresponding to a viscosity of 104 dPa.s. (ISO 7884-1)
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Working Range
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(Property) The range of surface temperature in which glass is formed into ware in a specific process. For comparative purposes, when no specific process is considered, the working range of glass is assumed to correspond to a viscosity range from approximately 103 to 108 dPa.s. (ISO
7884-1). |
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| [ X ] |
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| [ Y ] |
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| [ Z ] |
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