Microwave synthesis of LaCrO3

Abstract

The synthesis of LaCrO 3 from a stoichiometric mixture of Cr 2 O 3 and La 2 O 3 powder by microwave irradiation was examined using a multi-mode 28 GHz microwave heating system. In the La 2 O 3 -Cr 2 O 3 system, Cr 2 O 3 strongly absorbs microwaves while La 2 O 3 is transparent to microwaves. The reaction proceeded rapidly and LaCrO 3 could be synthesised within 15 min of irradiation. Surprisingly, the temperature required for the microwave synthesis (440°C) is much lower than that for conventional synthesis (>1200°C) using an electric furnace. The effect of the partial pressure of oxygen in the microwave chamber on the formation of LnCrO 3 was investigated. The formation of LnCrO 3 is enhanced with increase in the partial pressure of oxygen for Ln=La and Nd, while opposite behavior is seen for Ln=Gd, Tb, Dy and Ho.