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Title: Enhancement of the electrocaloric effect in PbZr0.7Ti0.3O3 ceramics via La doping: Driven by phase co-existence or defect effects?
Authors: Gözüaçık, Namık Kemal
Bayır, Mustafa Çağrı
Okatan, Mahmut Barış
Mısırlıoğlu, I. Burç
Alkoy, Sedat
Menşur Alkoy, Ebru
Gebze Teknik Üniversitesi
Gebze Teknik Üniversitesi
Izmir Institute of Technology
Sabancı Üniversitesi
Gebze Teknik Üniversitesi
Gebze Teknik Üniversitesi
Keywords: Electrocaloric effect
Phase coexistence
Thermodynamic modeling
Issue Date: Feb-2022
Publisher: Elsevier
Abstract: Lattice defects and their effects have been pivotal in studies of phase transitions in a wide range of materials. Introduction of such defects into a ferroelectric material through doping of secondary elements can be tailored towards specific applications but the mechanism through which the bulk properties change is seldom scrutinized. Here we study the effect of systematic La substitution into PbZr0.7Ti0.3O3 (PZT 70/30) ceramics whereby we analyzed the temperature dependent properties and estimated the temperature changes that could be induced upon application of an external electric field, namely the electrocaloric effect (ECE). Expecting the entropic changes to be maximal under an applied field, the suitability of the La doped PZT 70/30 system for EC applications had been a motivation to undertake the current task as this composition reportedly can host a rich variety of phases depending on La content including relaxor and antiferroelectric (AFE) states. An electrocaloric (EC) temperature change of 1.15 °C in a wide range of temperatures for 8% La doping at 45 kV/cm applied field was estimated from experimental data, the possible origins of which is discussed. We were able to explain the experimental results by adopting a Landau-Ginzburg based computational approach coupled with elasticity and electrostatics whereby La sites are treated as point defects in a PZT 70/30 lattice. The gradual slanting of the hystereses and reduction of the transition temperature in the samples with increasing La content is claimed to be a direct consequence of the electrical fields due to formation of dipolar defect complexes as backed by our simulations. The ECE is discussed in the light of the simulations and recent results for AFE ceramics.
Description: The authors would like to acknowledge the financial support of AFOSR through Grant No. FA9550–18–1–0450.
Appears in Collections:Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

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