Dresden 2017 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 3: Focus: Ferroics with Mesoscopic Order

DF 3.3: Vortrag

Montag, 20. März 2017, 10:30–10:50, WIL B321

Mechanisms of thermal depolarization and electromechanical response of lead-free relaxor/semiconductor composites — Lukas Riemer, Lalitha Kodumudi Venkataraman, Jürgen Rödel, and •Jurij Koruza — Technische Universität Darmstadt, Darmstadt, Germany

Thermal depolarization, i.e., vanishing of the macroscopic piezoelectric properties, is one of the major issues limiting the wide application of many lead-free piezoelectrics based on non-ergodic relaxors [1]. An increase of the depolarization temperature, T_d, was recently achieved by the formation of (3-0) composites of the (Na_0.5Bi_0.5)TiO₃-based relaxor phase and the ZnO semiconductor phase [2]. The aim of our work was to investigate the mechanisms responsible for this behaviour.

Composites consisting of the non-ergodic relaxor 0.94(Na_0.5Bi_0.5) TiO₃−0.06BaTiO₃ as the matrix phase and ZnO inclusions were prepared and a ferroelectric long-range order was found to be induced in virgin samples by residual thermal stresses. Moreover, an increase in the T_d of up to ≈ 40^∘C was observed. The ZnO inclusions had two counteracting influences on the thermal depolarization: stabilization of the induced ferroelectric state due to additional charges provided by the semiconductor and depolarization induced by residual thermal stresses. The results indicate possibilities for enhancing the thermal stability and operational range of lead-free relaxor piezoelectrics.

[1] J. Rödel et al., J. Eur. Ceram. Soc., 35, 1659 (2015)

[2] J. Zhang et al., Nat. Commun., 6, 6615 (2015)