Measuring lead scandium tantalate phase transition entropy by infrared camera

Pierre Lhéritier,Youri Nouchokgwe,Veronica Kovacova,Chang-Hyo Hong,Àlvar Torelló,Wook Jo,Emmanuel Defay

doi:10.1016/j.jeurceramsoc.2021.07.002

Abstract

Using an infrared camera, we measured the latent heat of the first order phase transition in lead scandium tantalate at different applied electric fields. The entropy change value of 3.4 J kg−1 K−1 is consistent with differential scanning calorimetry measurements. The advantage of such an approach stems from the possibility to obtain both adiabatic temperature change and latent heat of the phase transition material only with an infrared camera or a thermocouple. This may prove useful for a systemic characterization of first order electrocaloric materials.

Highlights

With recent advances in the field of caloric materials, new cooling technologies at a reasonable cost seem to be within reach
This paper presents a method of measuring the phase transition entropy change using an apparatus commonly employed to measure the adiabatic temperature change of a caloric material
By taking advantage of this, we presented a method to measure the entropy change ΔS associated to the first order phase transition of lead scandium tantalate

Summary

Introduction

With recent advances in the field of caloric materials, new cooling technologies at a reasonable cost seem to be within reach. The two main figures of merit are the adiabatic temperature change ΔT and the entropy variation ΔS induced by the application of an external field [1,2,3,4,5,6,7] In electrocalorics, both these quantities become significant near sharp first order transitions. More recently Malyshkina et al [16] showed how specific heat can be measured in ferroelectric materials far away from any phase transition where it can be considered as constant We build on these principles to present a new way of measuring the entropy of a first order phase transition. This should be mostly relevant for the study of electrocaloric materials and we applied it to one of its foremost representatives: lead scandium tantalate (PST).

Material and equipment

Adiabatic temperature change

Phase transition latent heat

Measurement and discussion

Limitations and ways of improvement

Conclusion