EFFECT OF ZrO۲ PARTICLE SIZE ON MORPHOLOGY and SYNTHESIS OF NANO CaZrO۳Via MOLTEN SALT METHOD

Well crystallized pure calcium zirconate (CaZrO۳ ) nanopowder was successfully synthesized using the molten-salt method. CaCl۲ , Na ۲CO۳, micro-ZrO ۲and nano-ZrO ۲ were used as starting materials. On heating, Na۲CO۳ reacted with CaCl ۲to form NaCl and CaCO ۳. Nano CaZrO ۳ was formed by reacting equimolar amounts of in situformed CaCO ۳ (or CaO) and ZrO ۲ in molten Na ۲CO۳-NaCl eutectic mixture. CaZrO ۳ particle size and synthesis temparture was tailored as a function of ZrO ۲particle size. Due to the usage of nano-ZrO ۲ , the molten salt synthesis (MSS) temperature was decreased and possible impurity phases in the final product were suppressed. The synthesis temperature was lowered to ۸۰۰°C and soaking time of the optimal synthesis condition was reduced to ۳h. After washing with hot-distilled water, the n-ZrO۲sample heated at ۸۰۰°C for ۳h, was single phase CaZrO ۳with ۷۰-۹۰ nm in particle size, while the m-ZrO ۲sample heated at ۱۰۰۰°C for ۳h, was single phase CaZrO ۳ with ۲۵۰-۴۰۰ nm in particle size. Based on the TEM observation and thermodynamic analysis, the synthesized CaZrO ۳ grains retained the morphology of the ZrO۲ nanopowders, which indicated that a template formation mechanism play a dominant role in synthesis process