Substitution of Bi and Nb Ions in Lead Zirconate-Titanate

Solid-state substitution of Bi and Nb ions in the perovskite crystal structure of Pb(Ti0.47Zr0.53)O3 was investigated by sample weight changes at 1150°C in an “equilibrium” PbO atmosphere. A model is discussed that includes the effect of charge neutralization, requiring weight losses for A-site substitutions and weight gains for B-site substitutions. Experiments support the substitution of Bi as Bi3+ on the Pb2+ A site and Nb as Nb5+ on the (Ti,Zr)4+ B site of lead zirconate-titanate. For each mole of BiO1.5 added to a specimen, 1.5 moles of PbO are lost; for each mole of NbO2.5 added, 0.5 moles of PbO are gained. These results agree with the proposed model and with ionic size arguments. The weight changes were time-dependent during the first 30 to 40 h at 1150°C. This behavior is accounted for by the presence of transient second phases.