Dielectric Characteristics of Perovskite-Structured High-Temperature Relaxor Ferroelectrics: The BiScO3–Pb(Mg1/3Nb2/3)O3–PbTiO3 Ternary System
A new compositional family of relaxor ferroelectrics was investigated based on the high-temperature Bi(Me)O3–PbTiO3 ferroelectric perovskite family. Compositions were fabricated near an estimated morphotropic phase boundary (MPB) of the xBiScO3–yPb(Mg1/3Nb2/3)O3–zPbTiO3 (xBS–yPMN–zPT) ternary system exhibiting high-temperature relaxor properties of Tmax∼250°–350°C and max∼10 000–24 000 at 1 kHz. Analysis of the low-field a.c. permittivity by a Vogel–Fulcher type dependence enabled key parameters of activation energy, EA, and freezing temperature, Tf, to be determined. The remanent polarization was studied over a broad temperature range and was observed to show classical ferroelectric square loop hysteresis behavior at temperatures T<Tf while slim loop hysteresis behavior was observed at temperatures Tf<T<Tmax. Pyroelectric current measurements were made and integrated to determine macroscopic polarization-temperature dependence, and were in excellent agreement with the hysteresis data. The macroscopic polarization was found to drop off rapidly near the freezing temperature, Tf. At temperatures T>Tmax, the deviation temperature, TD, was obtained from Curie–Weiss analysis and found to be ∼600°C. A comparison of characteristic electrical properties was made between the high-temperature perovskite relaxors and the classical complex lead relaxor compound, Pb(Mg1/3Nb2/3)O3 (PMN).
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