Shear resonance of lossy plates of lead-free Ba1-xCaxTi0.9Zr0.1O3 (x=0.1 and x=0.15) ceramics

Oral presentation given at the Electroceramics XV held in Limoges (France) on June 27-29th, 2016. Topic: FP3: Lead free piezoelectrics.The pseudo-binary Ba1-xCaxTi1-yZryO3 solid-solution system is attracting a great deal of interest nowadays as lead-free piezoceramics [1]. It was possible to achieve homogeneous and dense ceramics with good performance at moderate synthesis and sintering temperatures [2]. Poling of ferro-piezoelectric ceramic materials induces a cylindrical symmetry. This material is characterized by a set of ten independent piezoelectric, elastic and dielectric coefficients. Ferroelectrics present temperature and frequency dependence of the dielectric permittivity that must be taken into consideration when designing transducers [3]. Their properties must also be determined in complex form, thus accounting with all the material losses. A number of alternative methods of analysis of the complex impedance curve at resonance of piezoelectric ceramics were proposed in the last twenty years in order to obtain material parameters in complex form [4]. The automatic iterative method developed at Spanish CSIC was implemented for all the resonances and resonator shapes needed for the determination of all piezoelectric ceramic materials including losses, namely: radial and thickness extensional resonances of thin disk, thickness poled; shear resonance of a plate, thickness poled; and length extensional resonance of a long bar resonator, length poled. Measurements of material parameters at resonance were performed on ceramic shear plates, thickness-poled, and results were discussed in terms of the loss mechanisms of the ceramic