Synthesis of Pb(Mg1/3Nb2/3)O-3 in excess lead oxide by mechanical activation

Twenty hours of mechanical activation of mixed oxides at room temperature l ed to the formation of Pb(Mg1/3Nb2/3)O-3 (PMN) in excess PbO. The crystalli nity of the activation-derived perovskite PMN phase was further established when the activated PMN-PbO phase mixture was subjected to calcination at 8 00 degreesC. Pyrochlores, such as Pb3Nb4O13 and Pb2Nb2O7, were not observed as transitional phases on mechanical activation and subsequent calcination , although 50% excess PbO was deliberately added. The perovskite PMN phase was recovered by mashing off excess PbO using acetic acid solution at room temperature. It was sintered to a relative density of 98.9% of theoretical at 1200 degreesC for 1 h and the sintered PMN exhibited a dielectric consta nt of similar to 14 000 at 100 at and a Curie temperature of -11 degreesC.