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Phase Transitions and Phonon Mode Dynamics of Ba(Cu1/3Nb2/3)O3 and Sr(Cu1/3Nb2/3)O3 for Understanding Thermoelectric Response

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journal contribution
posted on 11.04.2020, 01:43 by Myung-Eun Song, Deepam Maurya, Yifei Wang, Jue Wang, Min-Gyu Kang, David Walker, Pam A. Thomas, Scott T. Huxtable, Robert J. Bodnar, N. Q. Vinh, Shashank Priya
We report electrical and thermal properties of perovskite-type Ba­(Cu1/3Nb2/3)­O3 (BCN) and Sr­(Cu1/3Nb2/3)­O3 (SCN). The BCN and SCN ceramics were synthesized by using the conventional solid state (CS) reaction method. The transmission electron microscopy analysis exhibited needle- and comb-type domain structures in BCN. Interestingly, SCN did not exhibit domain structure; however, it exhibited superlattice reflections due to ordering that were quite prominent in the selected area electron diffraction patterns. The temperature dependence of the dielectric response for BCN and SCN systems exhibits peaks due to structural phase transitions. The change in the Raman modes with increasing temperature also indicated the presence of phase transition in the temperature range 300–400 °C. BCN exhibited a lower value of the thermal conductivity (1.6 W/m·K at 600 °C) as compared to that of SCN (2.1 W/m·K at 600 °C) because of multiple phonon modes as identified through terahertz frequency domain spectroscopy.