Compositional effects on the optical and thermal properties of potassium aluminophosphate glasses

Abstract

The K2O–Al2O3–P2O5 glass system has been examined and various compositions have been melted. Their optical and thermal properties have been measured to assess their potential for athermalisation. The addition of alumina (Al2O3) increases the refractive index (n) and glass transition temperature (Tg) and decreases the thermal expansion coefficient (α), consequently leading to positive thermo-optic coefficient (dn/dT). In addition to thermal expansion, polarisability of the glass also affects dn/dT. Generally, glasses must exhibit negative dn/dT to counter thermal expansion, in order to have potential application in athermalisation.