[10a-W371-1~12] 22.1 Joint Session M "Phonon Engineering"

▼ [10a-W371-6] Anomalous Change of Heat Transfer in Sr(Ti,Nb)O₃ solid solution

〇(D)Yuqiao Zhang¹, Hai Jun Cho^1,2, Masashi Mikami³, Sungmin Woo⁴, Myung-Chul Jung⁵, Woosuck Shin³, Woo Seok Choi⁴, Myung Joon Han⁵, Hiromichi Ohta^1,2 (1.IST-Hokkaido Unv., 2.RIES-Hokkaido Unv., 3.AIST, 4.Sungkyunkwan Univ., 5.KAIST)

Keywords:Thermal conductivity, Sr(Ti,Nb)O3, Solid solution

In this study, using SrTi_1-xNb_xO₃ solid-solution (STNOss, 0.05 ≤ x ≤ 1) epitaxial films, we investigated heat transfer properties and observed anomalous behavior in the thermal conductivity. The lattice thermal conductivity (κ_lat) was extracted by κ_lat = κ_tot – κ_ele, where κ_tot is the total thermal conductivity measured by TDTR, and κ_ele is electron thermal conductivity calculated with the Wiedmann-Franz law. Steep increases in both κ_tot and κ_lat were observed around x~0.5, suggesting a phase transition from SrTiO₃-dominated phase to SrNbO₃-dominated phase. This phase transition is also supported by polaron effect, which only exits in SrTiO₃-dominated phase. Unlike the traditional alloy systems, SrNbO₃, which has larger average atomic mass, shows much higher κ_lat than SrTiO₃. According to the phonon dispersion calculations, SrTiO₃ shows much more intense scattering between optical and acoustic branches than SrNbO₃, which suppresses phonon mean free path for SrTiO₃. The Grüneisen parameters of SrTiO₃ were much higher than those of SrNbO₃, which will reduce the phonon transport properties.Our findings of heat transports in STNOss will be a fundamental contribution to the current knowledge in heat transportation and may be utilized to develop new TE materials.