Dielectric and ferroelectric properties and electric conductivity of sol-gel derived PBZT ceramics

(Pb1-xBax)(Zr1-yTiy)O-3 (PBZT) is a solid solution in which ferroelectric, relaxor or antiferroelectric properties are observed depending on composition. The substitution of Ba2+ into A position of the perovskite structure leads to the decrease in phase transition temperature and it gradually leads to relaxor properties. The majority of papers describe PBZT obtained from oxides. We report the results of the investigation of the properties and phase transitions of (Pb1-xBax)(Zr0.65Ti0.35)O-3 ceramics with x=0.09, 0.25 and 0.35 obtained by the sol-gel method with final free sintering (FS) at 1573 K/4 h and by the hot pressing (HP) method at 1473 K/2 h/20 MPa. Unlike pure PZT, the properties of HP-PBZT samples obtained at lower (1473 K) temperature are a little inferior than FS samples. It is probably related to the fact that barium requires higher final sintering temperatures. We present the results of XRD and dielectric measurements vs. temperature for PBZT ceramics. On the basis of dielectric measurements a. c. conductivity and activation energies have been calculated. In agreement with earlier literature data, we note that with the increasing Ba content T-m decreases and the maximum of e(T) is wider. However, we do not observe a shift of Tm with increasing frequency. The room P(E) hysteresis loops become more narrow and the polarization is smaller. The increase in dielectric losses with increasing temperature makes the measurement of hysteresis loops at low frequencies and high temperatures difficult. (C) 2011 Elsevier B. V. All rights reserved.