Quasi-indirect measurement of electrocaloric temperature change in PbSc0.5Ta0.5O3 via comparison of adiabatic and isothermal electrical polarization data

S Crossley,X Moya,N D Mathur,R W Whatmore

doi:10.1063/5.0037809

Abstract

Electrically driven adiabatic changes of temperature are identified in the archetypal electrocaloric material PbSc0.5Ta0.5O3 by comparing isothermal changes of electrical polarization due to the slow variation of electric field and adiabatic changes of electrical polarization due to the fast variation of electric field. By obtaining isothermal (adiabatic) electrical polarization data at measurement (starting) temperatures separated by &lt;0.4 K, we identify a maximum temperature change of ∼2 K due to a maximum field change of 26 kV cm−1 for starting temperatures in the range of 300 K–315 K. These quasi-indirect measurements combine with their direct, indirect, and quasi-direct counterparts to complete the set and could find routine use in the future.

Highlights

Our method was inspired by an analogous study of magnetocaloric gadolinium,20 and its application to EC materials, using much denser data, is novel
While slowly varying measurement temperature T with a cryogenic probe that was fabricated in house,24 we measured the isothermal electrical polarization using a Radiant Precision Premier II with a trek high-voltage amplifier, which integrated the displacement current that resulted from the application of a continuous triangular driving waveform of magnitude 26 kV cm−1 and period 30 s
The field sweep rates for measuring Piso(E) and Padi(E) were identified by scitation.org/journal/apm comparing one quarter of the cycle period with the thermal timescale, which was found to be ∼5 s via direct EC measurements of a mounted similar sample, and which could be determined without direct EC measurements by employing ever more extreme periods until there is no change to Piso(E) and Padi(E)

Summary

Introduction

Our method was inspired by an analogous study of magnetocaloric gadolinium,20 and its application to EC materials, using much denser data, is novel. Using these outer branches in E ≥ 0, we identify the nominally reversible adiabatic temperature change between any two points in Padi(E) as the temperature difference between the two Piso(E) plots that intersect these points.

Results

Conclusion