Dielectric Relaxation and Phase Transition in [Pb_0.94Sr_.06][(Mn_1/3Sb_2/3)_0.05(Zr_0.55Ti_0.45)_0.95]O₃ Ceramics

Abstract

A piezoelectric ceramic composition [Pb_0.94Sr_0.06][(Mn_1/3Sb_2/3)_0.05 (Zr_0.55Ti0₀.₄₅)_0.95]O₃ which is 6% Sr²⁺ substituted PZT ceramics with lead manganese antimonite as an additional hardener dopant is synthesized in pure perovskite phase by ceramic route. The X-ray diffraction of the sample at the room temperature shows an orthorhombic phase. The precursor [Pb_0.94Sr_.06]CO₃ is prepared by coprecipitation method to ensure homogeneous distribution of Sr²⁺ ions at A-site while the other columbite precursor MnSb₂O₆ is prepared by conventional solid state reaction method to prevent the formation of the unwanted pyrochlore phase. The field dependences of the dielectric response and conductivity are measured in a frequency range from 100 Hz to 1 MHz and in a temperature range from 300 k to about 775 k The dielectric measurements (real and imaginary parts) of this composition with temperature (300 k–775 k) at different frequencies (100 Hz–1 MHz) unambiguously point towards relaxor behaviour of the material. The real part of the dielectric constant is found to decrease with increasing frequency at different temperatures while the position of dielectric loss peak shifts to higher frequencies with increasing temperature indicating a strong dispersion beyond the transition temperature, a feature known for relaxational systems such as dipole glasses. The frequency dependence of the loss peak obeys an Arrhenius law with an activation energy 0.14 eV. The distribution of relaxation times is confirmed by Cole-Cole plots. The frequency-dependent electrical data are also analyzed in the framework of the conductivity and modulus formalisms. Both these formalisms yield qualitative similarities in the relaxation times. The SEM photographs of the sintered specimens present the homogenous structures and well-grown grains with a sharp grain boundary. The equality of the Curie and transition temperatures reveals that it undergoes second order phase transition

Keywords:

• Perovskite oxide
• dielectric relaxation
• phase transition

Acknowledgment

One of the authors (HS) is very thankful to Professor Dhananjai Pandey, School of Materials Science and Technology (SMST), IT, BHU for giving early acquaintances with this problem during the INSA visiting fellowship.