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DF: Fachverband Dielektrische Festkörper

DF 9: Poster Session DF

DF 9.11: Poster

Dienstag, 1. April 2014, 18:30–20:00, P1

Modified differential scanning calorimeter setup for the measurement of the electrocaloric effect in relaxor ceramics — •Mehmet Sanlialp, Vladimir Shvartsman, and Doru C. Lupascu — Institute for Materials Science, University Duisburg-Essen, Universitätsstr. 15, 45141 Essen, Germany

Demand for energy-efficient refrigeration technologies with a reduced environmental impact has stimulated interest to materials that exhibit the electrocaloric (EC) effect. The EC effect is a change of temperature or entropy of a dielectric material under an applied electric field at adiabatic or isothermal conditions, respectively. In spite of intensive studies of EC materials during the last 5 years, reliable direct measurements of the EC effect still remain a challenge. In this presentation we report on the development of an experimental setup based on a differential scanning calorimeter for EC measurements of bulk samples at quasi-isothermal conditions in the temperature range 150-500 K at applied electric fields up to 100 kV/cm. We performed EC measurements in several lead-containing and lead-free ceramics:

(1-x)PbMg_1/3Nb_2/3O₃-xPbTiO₃, (Pb_xLa_1−x)(Zr_yTi_1−y)O₃,

and(1-x)Ba(Zr_0.2Ti_0.8)O₃-x(Ba_0.7Ca_0.3)TiO₃.

Effects of temperature, electric field magnitude as well as a degree of relaxor behavior on the measured EC effect are discussed. Furthermore we compare the results of direct EC measurements with indirect EC estimations based on the Maxwell relations to judge the compatibility of these two measurement methods.