The effects of raw materials particle size and salt type on formation of nano-CaZrO3 from molten salts

Abstract

Nano-CaZrO3 was successfully synthesized at 800°C using the molten-salt method, and the effects of salt type and raw materials particle size on the formation of CaZrO3 were investigated. Na2CO3, CaCl2, nano-ZrO2 and micro-ZrO2 were used as starting materials. On heating, Na2CO3 reacted with CaCl2 to form NaCl and in situ CaCO3. Na2CO3–NaCl molten eutectic salt provided a liquid medium for reaction of CaCO3 and ZrO2 to form CaZrO3. The results demonstrated that in both nano- and micro-ZrO2 inclusive samples, CaZrO3 started to form at about 700°C and that, after the temperature was increased to 1000°C, the amounts of CaZrO3 in the resultant powders increased with a concomitant decrease in CaCO3 and ZrO2 contents. After washing with hot-distilled water, the samples containing nano- and micro-ZrO2 heated for 3h at 800°C and 1000°C, were single-phase CaZrO3 with 70–90nm and 400–450nm particle size, respectively. Also, the synthesis process was completed in lower temperatures using eutectic salts. Furthermore, the synthesized CaZrO3 particles retained the size and morphology of the ZrO2 powders, which indicated that a template formation mechanism dominated the formation of CaZrO3 by molten-salt synthesis.