Thermal Expansion Studies in the Lead iron Niobiat - Lead Titanate System

Compositions in the solid solution series $\{Pb(Fe_{0.5}Nb_{0.5})0_3\}_{1-x}- \{PbTiO_3\}_x$ $(x = 0 ->1)$ were prepared by'solid state reaction. The phase transition from rhombohedral/tetragonal to cubic structure has been studied as a function of x by differential thermal analysis, high temperature x-ray diffraction and dilatometry in the temperature range 298-773K. Dielectric measurements and thermal expansion coefficients of the x=0.2 composition indicate that the relaxor type behiviour of lead iron niobate is extended up to 453K

Investigation of tetragonal distortion in the PbTiO3PbTiO_3 – BiFeO3BiFeO_3 system by high-temperature x-ray diffraction

Compositions in the $(Pb_{1-x}Bi_x)$ $(Ti_{1-x}Fe_x)O_3$ solid solution system for x $\leq$ 0.7 show unusually large tetragonal distortion. High-temperature x-ray diffraction was used to study the tetragonal distortion as a function of temperature (25–700 $^oC$) for compositions (x - 0–0.7) using powders prepared by solid-state reaction in the above system. Large changes in the lattice parameters were observed over a narrow temperature range near Curie temperature $(T_C)$ for compositions near the morphotropic phase boundary (MPB)x $\simeq$ 0.7). Compositions near MPB showed a c/a ratio of 1.18 at room temperature. Polar plots of lattice constants at different temperatures indicated strong anisotropic thermal expansion with zero thermal expansion along the [201] direction

Piezoelectric materials for high temperature transducers and actuators

Piezoelectric sensors and actuators are a mature technology, commonplace amongst a plethora of industrial fields including automotive, maritime and non-destructive testing. However the environments that these devices are required to serve in are becoming more demanding, with temperatures being driven higher to increase efficiencies and reduce shut-downs. Materials to survive these temperatures have been the focus of many research groups over the last decade, but there still remains no standard for the measurement of piezoelectric materials at high temperature. This is required to effectively determine comparable Figures of Merit into which devices can be successfully designed. As part of a recent European effort to establish metrological techniques for high temperature evaluation of electro-mechanical properties, we present here a review of the most promising high temperature polycrystalline materials. Where their properties allow operation above that of the ubiquitous commercial material lead zirconate titanate, as well as work done to modify a promising high temperature system, for use as a material standard