Ferroelectric and Structural Properties of the Pb(Sc _1/2 Nb _1/2 ) _1‐x ,Ti _x ,O ₃ System

Abstract

Extensive solid solution was observed in the system Pb(Sc 1/2 /,Nb 1/2 ,) 1‐x ,Ti x ,O 3 . In the range 0 ≤ x ≤ 0.425 a rhombohedral ferroelectric phase was stable at 25° C. In the range 0.45 ≤ x ≤ 1.00 a tetragonal ferroelectric phase was stable at this temperature. The phase diagram of the system below 500° C strongly resembles that of PbZrO 3 −PbTiO 3 . The compound Pb(Sc 1/2 Nb 1/2 )O 3 exhibited rhombohedral perovskite cell symmetry below the ferroelectric ↔ paraelectric transition temperature, and the angle a was acute. The radial coupling coefficient was 0.46 for the composition Sc 1/2 Nb 1/2 ) 0.575 Ti 0.4250 O 3 . At 25°C this composition consisted primarily of the rhombohedral phase with a small amount of the tetragonal phase present. The ferroelectric ↔ paraelectric transition occurred over a temperature range in the rhombohedral phase field. The spontaneous polarization was finite at temperatures considerably above the temperature of the permittivity maximum for a given rhombohedral solid solution.