Phase transitions in PbTiₓHf₁₋ₓO₃ determined by thermal analysis and impedance spectroscopy

Abstract

The objective of this study is to determine the influence of partial substitutions of Ti⁴⁺ by isovalent Hf⁴⁺ in the perovskite-type crystalline structure of PbTiO₃. Different samples over the whole composition range (0 ≤ x ≤ 1) in the PbTi₁₋ₓHfₓO₃ family have been prepared. Phase transitions have been determined by thermal analysis (differential scanning calorimeter: DSC) and complex impedance spectroscopy (IS) over a wide temperature range. As a consequence of the cation replacement the changes that take place in the different phase transition temperature are reported. By both techniques, thermal analysis and electrical characterization, it is shown that for all compositions prepared there is only one phase transition in a temperature range between 230 and 460 °C. With these results and the previously known crystalline structure of pure PbTiO₃ and PbHfO₃ perovskites, the phase diagram of the PbTi₁₋ₓHfₓO₃ family is presented including a morphotropic phase transition at x ~ 0.5.