PREPARATION OF LEAD-CONTAINING PEROWSKITE-TYPE COMPOSITE OXIDE

摘要

PURPOSE:To prepare the titled composite oxide having high content of perowskite-type crystal and high degree of pulverization, by the hydrothermal reaction of PbO and hydrated Ti acid and Zr acid having specific hydration degree in an aqueous medium under stirring. CONSTITUTION:PbO and a compound of formula MO2.nH2O (M is Ti or Zr; 1=n7) are dispersed in an aqueous medium, and subjected to hydrothermal reaction at about 110-120 deg.C under stirring. By selecting the value of (n) within the above range, the crystallinity of PbO.MO2 produced by the hydrothermal reaction and its calcined product can be remarkably improved. The MO2.nH2O can be prepared e.g. by neutralizing an aqueous solution of Ti nitrate with NH4OH at high temperature, in the form of the precipitate of hydrated Ti acid. The degree of hydration depends upon the precipitation temperature, and higher temperature results in lower hydration degree. A precipitate from which the contaminant ions can be completely removed, and having fine particle size and excellent filtering characteristics, can be obtained by adjusting the time constant for the addition of NH4OH at a proper level, and carrying out the precipitation under vigorous agitation. The stirring in the hydrothermal reaction makes the reaction uniform, and improves the yield of the perowskite-type crystal.