Piezoelectricity from Elastic and Dielectric Measurements on Unpoled Ferroelectrics

A method is described to assess the piezoelectric response of ferroelectric materials from the temperature dependence of the elastic moduli and dielectric constant of unpoled samples. The limits and advantages over the traditional methods on poled samples are discussed. A quantitative check is made by comparing the piezoelectric softening measured below the ferroelectric transition in the Young's modulus of unpoled ceramic BaTiO3, with the appropriate angular average of the single crystal material constants from the literature. The softening effect of porosity has been taken into account by comparing the moduli of samples with different densities.