Temperature Dependence of the Piezoelectric Coefficient in BiMeO₃‐PbTiO₃ (Me = Fe, Sc, (Mg_1/2Ti_1/2)) Ceramics

Abstract

The piezoelectric coefficient of high temperature piezoelectric ceramics, denoted as Bi(Me)O3‐PbTiO3, (Me = Fe, Sc, (Mg1/2Ti1/2)) 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 (Td), defined as the inflection point in a temperature‐dependent d33 plot. Measured Td 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 Td. It was also shown that Td matches with the temperature where the dielectric anomaly initiates, and hence Td from the d33 measurement is consistently lower than that from the dielectric permittivity measurement. It is proposed that this discrepancy in the position of Td is due to the fact that the depolarization occurs in two steps.

Determination of depolarization temperature of (Bi1/2Na1/2)TiO3-based lead-free piezoceramics

“…The displacement of the sample surface was measured through a hole in the porous alumina lid of the furnace by a laser Doppler vibrometer (Polytec sensor head OFV-505 and front-end VDD-E-600) during heating and recorded by Polytec Vibrometer software (Vibsoft4.5). 50 …”

High temperature measurement and characterisation of piezoelectric properties

“…This technique, particularly suited to higher frequency measurements, can be adapted for measurement of piezoelectric movement at high temperature. Examples of the use of this technique include LDV measurements at 1 kHz of piezoelectric d 33 coefficients at temperatures up to 500 °C which were correlated with temperature-dependent XRD measurements [23] and measurement of the response of piezoelectric composites in the range 0.1-10 kHz at more moderate temperatures between -50 °C and +50 °C [28] …”

“…Whilst these techniques don't directly measure the piezoelectric effect, they are powerful tools for gaining information on strain in the crystal lattice and phase transitions [20], and the contributions of domain wall motion [21] and domain switching [22] to the piezoelectric coefficients. Diffraction studies of piezoelectric materials at temperatures up to 500 °C have helped understand the relationship between polarisation changes, piezoelectric properties and structural transformations in bismuth ferrite -lead titanate and related ceramics [23]. …”

Strain Mechanisms in Lead-Free Ferroelectrics for Actuators

“…Further details on the device are presented elsewhere. 384 All compositions were measured in the temperature range from 25 °C to 105 °C with a heating rate of 2 °C/min in 5 °C steps. A sinusoidal wave of 0.01 kV/mm amplitude and a frequency of 10 kHz was chosen as input voltage (function generator HM8131-2, Hameg GmbH, Germany).…”