Preparation and thermal effects of Al_2O_3/LaPO_4 ultrafine mixed powder from commercial alumina sol

摘要

The Al_2O_3/LaPO_4 mixed powders prepared from a commercial alumina sol and a solution of La(NO_3)_3. In the case of pure Al_2O_3, #delta#-Al_2O_3 already formed by heating up to 700 deg C, and #alpha#-Al_2O_3 formed at temperatures ranging form 1150 to 1200 deg C. In the case of 90 vol percent Al_2O_3 /l0 vol percent LapO_4, the phase transformation into the #alpha#-Al_2O_3 took place above 1350 deg C. It is suggested that the LapO_4 fine particles lied between the #theta#-Al_2O_3 particles suppress the phase transformation into #alpha#-AL_2O_3. The fired bulk densities of the Al_2O_3/LaPO_4 composite bodies were less than 80 percent of the theoretical density. These low fired bulk densities are owing to low green bulk densities and the decreasing of the specific surface area with increasing the calcination temperature.