1) Glass materials
Phosphate glass due to a low glass transition temperature, moderate phonon energy, high coefficient of thermal expansion, high solubility of rare earth ions, good spectral properties of rare earth ions in it, low non-linear refractive index, ultraviolet transmission, low dispersion and other advantages, has become a more used optical glass media, widely used in the field of coloured filtering, optical fibres and laser materials; However, phosphate glass melting on the refractory crucible erosion larger and less stable, to a certain extent hindering their application. Experimental studies have shown that changing the glass composition and introducing aluminium, boron and rare earth elements can effectively improve the chemical stability of phosphate glasses. Fe2O3 + NH4H2PO4 and Fe2O3 + NH4H2PO4 + Ce2CO3 with n(Fe)/n(P) of 0.67 were used as raw materials to prepare iron phosphate glass and caesium-doped iron phosphate glass, respectively, and the thermal expansion of the glass samples was determined by differential scanning calorimetry at 26.85-426.85 °C in an air atmosphere and in a flowing argon atmosphere, respectively. The thermal expansion and specific heat of the glass samples were determined by differential scanning calorimetry (DSC) at 26.85-426.85 ℃ in air and under flowing argon atmosphere respectively. The thermal expansion of the iron phosphate glass increased with the increase of caesium content and the specific heat decreased with the increase of caesium content, indicating that caesium doping reduced the stability of the iron phosphate glass.