Thermal decomposition and evolved gas analysis of neodymium-doped yttrium aluminum garnet precursor prepared by co-precipitation

The thermal decomposition of amorphous neodymium-doped yttrium aluminum garnet (Nd:YAG) precursor, prepared by co-precipitation with ammonium hydration carbonate as precipitator, was studied in flowing air. Four weight loss stages were observed in the TG curve. At the first stage, NH3, H2O, NO, NO2 and CO2 were released owing to the evaporation of adsorbed water and ammonia water and the decomposition of residual ammonium salts below 150 °C. The structural decomposition of NH4+and H2O in the precursor molecule was decomposed at the second stage from 150 °C to 220 °C. The evolution of NO, NO2 and CO2 were verified in the last two stages because of the formation of metal oxides at high temperature. Moreover, YAG phase started to develop without an intermediate phase when the precursor was calcined at about 900 °C. However, the structural CO32− contained in the precursor molecule was not completely eliminated at 900 °C.

► Amorphous Nd:YAG precursor prepared by co-precipitation was studied by TG–DSC, TG–FTIR and TG–QMS. ► Absorbed water, ammonia water and residual NH4HCO3 were mainly decomposed under 150 °C. Constituent NH3 and H2O were released completely at about 220 °C. ► The evolution of CO2, NO, and NO2 gases consisted of four stages. ► Phase-pure YAG could be formed without an intermediate phase when the precursor was calcined at 900 °C.