Polar Transition-Metal Chalcogenide: Structure and Properties of the New Pseudo-Hollandite Ba0.5Cr5Se8

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• 作者：Robin Lef猫vre ; David Berthebaud ; Olivier Perez ; Denis Pelloquin ; Sylvie H茅bert ; Franck Gascoin
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：October 27, 2015
• 年：2015
• 卷：27
• 期：20
• 页码：7110-7118
• 全文大小：441K
• ISSN：1520-5002

文摘

Single crystals of the new ternary selenide Ba_0.5Cr₅Se₈ were synthesized using a self-flux method in fused silica tubes. This new phase was first considered to crystallize in the usual monoclinic symmetry for pseudo-hollandite compounds. However, single-crystal X-ray diffraction study showed unambiguously that Ba_0.5Cr₅Se₈ crystallizes in the P1虆 triclinic space group with cell parameters a = 9.5084(4) 脜, b = 7.1788(3) 脜, and c = 8.9296(4) 脜 and 伪 = 89.9979(16)掳, 尾 = 104.3958(22)掳, 纬 = 100.8869(17)掳, and Z = 2. Bulk samples were prepared by solid-state reaction and sintered using a spark-plasma sintering device. A combination of powder X-ray diffraction and transmission electron microscopy was used to perform structural analysis on spark plasma sintering prepared samples. Ba_0.5Cr₅Se₈ orders antiferromagnetically with T_N = 58 K and shows a semiconducting behavior with 蟻_300K = 0.35 惟路cm and S_300K = 230 渭V路K^鈥?. A maximum of the Seebeck coefficient of 315 渭V路K^鈥? occurs at 635 K with 蟻_635K = 0.14 惟路cm, while the thermal conductivity remains low and constant at about 0.8 W路m^鈥?路K^鈥? from room temperature up to 873 K, leading to a maximum ZT of 0.12 around 800 K. A remarkably large increase of thermal conductivity is observed in the antiferromagnetic state.