EFFECTS OF METAL-SALTS ON THE THERMAL-DECOMPOSITION OF EDTA-GEL PRECURSORS FOR FERROELECTRIC CERAMIC POWDERS

Raw chemicals such as metal nitrates and chlorides were found to affec t the thermal decomposition behaviour of EMTA-gel precursors used for the production of ceramic powders. Fine, homogeneous ceramic powders w ere produced from nitrate solutions while chlorides gave segregated ph ases. In studies on the production of lead zirconate titanate (PZT) us ing chlorides, the segregation and loss of lead was observed and shown to be caused by the formation and evaporation of PbCl2. Thermal analy sis (DTA/TG) quantitatively proved the suggested reaction mechanism fo r this phase segregation. Crystallization of the desired perovskite ph ase of lead zirconate titanate (PZT) and barium titanate (BT) initiate d at temperatures as low as 250 degrees C in the nitrate EDTA precurso rs. Water of crystallization and formation of BaCO3 in the barium tita nate precursor were suggested to account for differences in the observ ed decompositional behaviours of the BT and PZT precursors.