The effects of raw materials particle size and salt type on formation of nano-CaZrO_3 from molten salts

摘要

Nano-CaZrO_3 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 CaZrO_3 were investigated. Na_2CO_3, CaCl_2, nano-ZrO_2 and micro-ZrO_2 were used as starting materials. On heating, Na_2CO_3 reacted with CaCl_2 to form NaCl and in situ CaCO_3. Na_2CO_3-NaCl molten eutectic salt provided a liquid medium for reaction of CaCO_3 and ZrO_2 to form CaZrO_3,. The results demonstrated that in both nano- and micro-ZrO_2 inclusive samples, CaZrO_3 started to form at about 700 °C and that, after the temperature was increased to 1000 °C, the amounts of CaZrO_3 in the resultant powders increased with a concomitant decrease in CaGO_3 and ZrO_2 contents. After washing with hot-distilled water, the samples containing nano- and micro-ZrO_2 heated for 3 h at 800 °C and 1000 °C, were single-phase CaZrO_3 with 70-90 nm and 400-450 nm particle size, respectively. Also, the synthesis process was completed in lower temperatures using eutectic salts. Furthermore, the synthesized CaZrO_3 particles retained the size and morphology of the ZrO_2 powders, which indicated that a template formation mechanism dominated the formation of CaZrO_3 by molten-salt synthesis.