INFLUENCE OF PIEZOELECTRIC ANISOTROPY ON ELECTROMECHANICAL PERFORMANCE OF ULTRASOUND NDT PROBES AT ELEVATED TEMPERATURES

When designing an ultrasound non-destructive (NDT) probe for high temperature applications, one has to take into account a multitude of temperature induced effects, such as the temperature dependence of key physical properties of probe materials. In this paper, the significant influence of temperature change on piezoelectric properties and piezoelectric anisotropy, and thus on the ultrasound properties of the whole probe, is discussed theoretically. This is demonstrated within the thermodynamic Landau-Ginzburg-Devonshire (LGD) framework and the KLM model of equivalent circuits for two different piezoelectric, acoustically active probe materials from the same family - barium titanate and lead titanate. These two materials are model materials for the whole family of piezoelectric perovskites, including the commercially widely used PZT and relaxor ferroelectrics PMN-PT and PZN-PT