Preparing 2Y-TZP Nanopowder by a Coprecipitation Method with NH_4HCO_3 as the Precipitant

2Y-TZP nanopowder was prepared by a coprecipitation method, using NH4HCO3, ZrOCl2-9H2O and Y(NO3)3 as the starting materials. During the precipitating process, (NH4)3ZrOH (CO3)3-2H2O was formed through a two-step reaction. First, NH4HCO3 reacted with ZrOCl2·9H2O to form Zr(OH)4, then NH4HCO3 further reacted with Zr(OH)4 to form (NH4)3ZrOH(CO3)3·2H2O. The resulting (NH4)3ZrOH(CO3)3-2H2O was unstable and decomposed into ZrO2, NH3, H2O and CO2 at about 130℃. The 2Y-TZP powders obtained by calcining the precipitate mixture at 300℃and 450℃ showed very fine particle sizes and were almost free of large hard aggregates. Furthermore, these powders showed good sinterability and could be highly densined at a low temperature of 1225℃.