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The piezoelectric coefficient of high temperature piezoelectric ceramics, denoted as Bi(Me)O 3 ‐ PbTiO 3 , ( Me = Fe , Sc , ( Mg 1/2 Ti 1/2 )) was investigated as a function of temperature by using a custom‐designed test frame. Utilizing laser vibrometry, it was possible to assess the piezoelectric coefficient in situ in the range from room temperature to 500°C. The constraints on the sample geometry as they exist in the commonly used resonance/antiresonance technique such as those encountered during poling were circumvented by the use of the converse piezoelectric effect. Comparison with literature data revealed that the current method is a useful alternative for determining the depolarization temperature ( T d ), defined as the inflection point in a temperature‐dependent d 33 plot. Measured T d for each poled specimen was compared with that determined by dielectric permittivity as well as temperature‐dependent X‐ray diffraction data to understand a possible origin of T d . It was also shown that T d matches with the temperature where the dielectric anomaly initiates, and hence T d from the d 33 measurement is consistently lower than that from the dielectric permittivity measurement. It is proposed that this discrepancy in the position of T d is due to the fact that the depolarization occurs in two steps.
Leist et al. (Fri,) studied this question.