Analysis of the preparation of In-doped CaZrO3 using a peroxo-oxalate complexation method

The wet chemical synthesis of CaZr0.9In0.1O3 - alpha powders via a peroxo-o xalate complexation method has been studied in detail using different techn iques, i.e. TG-DTA, XRD, FT-IR, BET, SEM, EDX, and non-isothermal densifica tion. Using these techniques, the different reaction steps in the calcinati on process have been clarified. After drying the precipitated complex at 15 0 degreesC for 3 h, a mixture of calcium oxalate and an amorphous zirconia phase is found. Between 200 and 450 degreesC, the calcium oxalate decompose s into calcium carbonate. In the temperature range 450-800 degreesC, the ca lcium carbonate decomposes into CaO, while a crystalline zirconia phase app ears (CaZr4O9). In this temperature range, the formation of CaZrO3 is alrea dy observed. Further increasing the calcination temperature to 1000 degrees C leads to a binary mixture of CaZrO3 and CaIn2O4. When the calcination tem perature is increased to around 1500 degreesC, the CaIn2O4 phase dissolves into the calcium zirconate to form the desired CaZr0.9In0.1O3 - alpha. All compacts sintered at 1550 degreesC for 10 epsilonh show single-phase CaZr0. 9In0.1O3 - alpha, independent of the calcination temperature. The morpholog y of the sintered compacts, however, varies with the calcination temperatur e, due to the presence or absence of a reactive sintering step around 1300 degreesC. Powders calcined at 1000 degreesC show a larger grain size in the sintered compact than powders calcined at 1450 or 1550 degreesC.