Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 20: Poster I

HL 20.19: Poster

Tuesday, March 18, 2025, 10:00–12:30, P3

The impact of Bi and Na non-stoichiometry on the electrocaloric effect in (Na0.5Bi0.5)TiO3-BaTiO3 ceramics — •Sobhan M. Fathabad, Mohammadamin H. Kashani, Eva Kröll, Vladimir V. Shvartsman, and Doru C. Lupascu — Institute for Materials Science and Center for Nanointegration Duisubrg-Essen (CENIDE), University of Duisburg Essen, Essen, Germany

The electrocaloric effect (ECE) is the phenomenon where polar crystals experience a change in isothermal entropy or adiabatic temperature in response to the application or removal of an electric field. In this work, we investigate the influence of Bi and Na non-stoichiometry on the depolarization mechanism and electrocaloric effect in BaTiO3 - (Na0.5Bi0.5)TiO3 compounds at the morphotropic phase boundary. Ceramic samples were prepared using the solid-state synthesis method. The polarization hysteresis loops were measured in the temperature range from -20 °C to 200 °C and subsequently the ECE was indirectly estimated in the framework of the thermodynamic approach based on the Maxwell relation. The depolarization temperature was studied using dielectric permittivity, X-ray diffraction, and pyrocurrent analysis. Direct measurements of the ECE were conducted using a quasi-adiabatic calorimeter. It was shown that the introduced defects reduce the depolarization temperature, consequently shifting the maximum ECE towards room temperature.

Keywords: Electrocaloric Effect; depolarization temperature; (Na0.5Bi0.5)TiO3; BaTiO3; non-stoichiometry