The reaction of neodymium(III) oxide with chromium(III) oxide

Abstract

The reaction of Nd 2O 3 and Cr 2O 3 in air has been studied in the temperature range 350–950°C. The nature and quantity of products formed was investigated primarily by an analytical scheme developed to permit the determination of the amounts of unreacted Nd 2O 3 and Cr 2O 3 and the amounts of possible products. From 350–600°C the sole product was Nd 2(CrO 4) 3, from 630–840°C the products were Nd 2(CrO 4) 3 and NdCrO 3, and from 880 to 950°C the sole product was NdCrO 3. The variation with temperature of the amounts of products formed at constant reaction time was investigated. The kinetics of the reaction were investigated at the following temperatures, 630, 650, 680, 700, 720 and 760°C. At each temperature, with increasing time the amount of Nd 2(CrO 4) 3 formed increased to a maximum and then decreased whereas the amount of NdCrO 3 formed increased continually. The results together with experiments on the effect of oxygen and argon atmospheres are interpreted as follows. NdCrO 3 is not formed by direct combination of Nd 2O 3 with Cr 2O 3. Instead the reaction of the two oxides produces Nd 2(CrO 4) 3, the thermal decomposition of which then leads to the formation of NdCrO 3. The absence of NdCrO 4 as a reaction product is investigated and discussed as is the absence of NdCrO 3 as a reaction product below 630°C.