Phase equilibria and electrical properties of barium-containing relaxor-based solid solutions

We have studied the effect of modification with Ba on the phase composition, structure, and electrical properties of ceramic samples of Pb(1−x)Bax(Mg1/3Nb2/3) m (Zn1/3Nb2/3) y (Ni1/3Nb2/3) n Ti z O3 (0 ≤ x ≤ 0.15) solid solutions and investigated phase equilibria in this system in the range 0 ≤ x ≤ 0.15. The results indicate that a tetragonal and a low-symmetry phase coexist in the composition range 0 ≤ x ≤ 0.05, a pseudocubic phase exists in the range 0.05 < x < 0.10, and a cubic phase exists in the range 0.1 ≤ x ≤ 0.15. We propose a scheme of solid-solution formation according to which partial barium substitution for lead in the range 0 ≤ x ≤ γ (where γ is structural nonstoichiometry) causes the Pb ions to leave distorted octahedra. For x > γ, Ba2+ substitutes for Pb2+ on the cuboctahedral site. The sintering temperature is shown to influence the phase composition of the modified ceramics. We demonstrate, that varying the Ba content of the solid solutions, one can obtain a series of materials with a wide range of electrical parameters (ɛ/ɛ0 = 2880–11000, K p = 0.07–0.43, and Q m = 48–8300) and potential applications in hydroacoustics, piezoelectric motors, and capacitor technology.