New Relaxors with the Perovskite Structure

Abstract

Perovskites PbBO₃ with multiple substitutions in the B-positions were synthesized. Ceramic samples with n = 2–6 (n is the number of different B-ions) were studied using X-ray diffraction, and measurements of dielectric permittivity at frequencies 12 Hz–100 kHz and temperatures 77–450 K. It has been shown that the samples are of the perovskite structure, they undergo phase transitions from disordered to ordered phase, and their dielectric behavior is typical for relaxors. The order-disorder phase transitions proceed with the unit cell doubling. Based on this and in accordance with random site model, the B-ion distribution over two sublattices is discussed.

Keywords:

• Perovskites
• relaxors
• order-disorder
• phase transitions
• X-ray diffraction
• dielectric properties

PACS numbers:

• 61.05.cp
• 64.60.Cn
• 81.30.Hd

V. Acknowledgments

This volume of FERROELECTRICS is dedicated to George Taylor, yet the present paper is on relaxors. Why? The answer is very simple. First, ferroelectrics are the favorite field of George Taylor, the Founder and Editor-in Chief of the journals FERROELECTRICS and INTEGRATED FERROELECTRICS, and relaxors are ferroelectrics or, at least, ferroelectric related materials. Second, energy-related problems are George Taylors’ favorite topic in which he is one of the pioneers; and, because relaxors possess unique giant electromechanical coefficients, they may be regarded as the most promising materials for energy conversion.

The author would also like to express his sincere thanks to his colleagues O.E. Kvyatkovsky, P.A. Markovin, V.K. Yarmarkin, and V.G. Zalessky, for numerous discussions.

This study was partly supported by the grant Scientific School 2628.2008.2 and the Program of the Department of Physical Sciences of the Russian Academy of Sciences.