Effects of niobium addition on the relaxor ferroelectric properties and ordering structures of lead iron tantalates

Pyrochlore-free Pb(Fe1/2Ta1/2)O-3, Pb(Fe1/2Nb1/2)O-3, and complete series of solid solutions between them were fabricated and their ordering structures as well as their dielectric properties were investigated. The dielectric properties of Pb(Fe1/2Ta1/2)O-3 were those of typical relaxor ferroelectrics showing evident dielectric relaxation and diffusive phase transition, but the degrees of diffusive phase transition and dielectric relaxation decreased as Ta5+ was replaced by Nb5+. Also, the Fe3+ and Ta5+ ions of Pb(Fe1/2Ta1/2)O-3 were ordered within the nanoscale region, but the degree of ordering decreased as Ta5+ was replaced by Nb5+. The loss of relaxor ferroelectric characteristics in Pb(Fe1/2Ta1/2)O-3 with the replacement of Ta5+ by Nb5+ was correlated with the weakening of the ordering.