Enhanced processing of perovskite Pb(Mg1/3Nb2/3)O3 relaxors through understanding the surface chemistry of the component powders

It is well known that the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) is difficult to prepare in the perovskite form without the appearance of pyrochlore phases(s). The appearance of pyrochlore is related to the reactivity of the refractory oxide MgO in relation to the other phases in the PbO-Nb2O5 binary system. Ceramic processes that improve the reactivity of the oxide MgO, such as better mixing/milling-dispersibility enhance the formation of the perovskite phase. Characterization of the surface chemistry of the component powders, Nb2O5, PbCO3 and MgCO3, especially in terms of their isoelectric points revealed that electrostatically dispersed suspensions could be realized at pH levels>11. In conjunction with high energy attrition mixing/milling, very homogeneous and reactive powder could be achieved. Upon calcination, the formation of pyrochlore was greatly suppressed