Meaning
State variable in glass science that captures the temperature at which the liquid structure was frozen into a solid during cooling. Rapid quenching results in a high fictive temperature, while slow cooling allows the structure to rearrange into a configuration characteristic of a lower temperature. This value determines the physical properties of the glass, including density, refractive index, dispersion and chemical durability.
Structural Configuration
Molecular arrangements in amorphous solids do not change instantaneously with external temperature changes. Instead, fictive temperature tracks the effective age of the structure by mapping its current volume or enthalpy to an equivalent equilibrium liquid state. A discrepancy between the actual temperature and the fictive value drives the relaxation process toward equilibrium.
Process Calibration
Fiber optic production and precision lens molding rely on managing the rate at which the material solidifies. If the fictive temperature is inconsistent across a batch, the resulting variation in refractive index can lead to signal loss or optical distortion. Engineers use heat treatment cycles to reset this variable to a uniform value.
Yield Consequence
Prematurely exiting the cooling phase increases internal stresses within the glass matrix. High fictive values correlate with lower fracture toughness and higher susceptibility to environmental stress corrosion. Controlling the cooling rate ensures the final product meets the demonstrated rate of performance required for high-reliability applications.
