Structural and dielectric properties of the phase Pb 1−2xK xM 3+xNb 2O 6, M = La or Bi

Abstract

The Pb 1−2xK xM 3+ xNb 2O 6, M = La or Bi, solid solutions have been prepared by solid state reaction and their structural and ferroelectric properties have been established. Complete crystalline solid solubility exists in both systems; in addition, three structurally related phases, namely, the ferroelectric orthorhombic and tetragonal tungsten bronze phases and the paraelectric tetragonal K. 5La. 5Nb 2O 6 type phase, have been identified at room temperature. The composition ranges for three phases are 0.0 ≤ x ≤ 0.47, 0.48 ≤ x ≤ 0.85, 0.86 ≤ x ≤ 1.0, respectively. The ferroelectric phase transition temperature, T c, decreases with increasing concentration of K + and La 3+ or Bi 3+ in the orthorhombic tungsten bronze phase. A few compositions from each system exhibit excellent dielectric and piezoelectric characteristics, indicating that they could be future materials for piezoelectric and high frequency dielectric studies.