BaGe₆ and BaGe_6‑x: Incommensurately Ordered Vacancies as Electron Traps

We report the high-pressure high-temperature synthesis of the germanium-based framework compounds BaGe6 (P = 15 GPa, T = 1073 K) and BaGe6–x (P = 10 GPa, T = 1073 K) which are metastable at ambient conditions. In BaGe6‑x, partial fragmentation of the BaGe6 network involves incommensurate modulations of both atomic positions and site occupancy. Bonding analysis in direct space reveals that the defect formation in BaGe6–x is associated with the establishment of free electron pairs around the defects. In accordance with the electron precise composition of BaGe6‑x for x = 0.5, physical measurements evidence semiconducting electron transport properties which are combined with low thermal conductivity.本工作报道了锗基骨架化合物BaGe₆（压力P=15 GPa，温度T=1073 K）与BaGe₆₋ₓ（压力P=10 GPa，温度T=1073 K）的高温高压合成，该类化合物在常压环境下为亚稳态。在BaGe₆₋ₓ体系中，BaGe₆骨架发生部分碎裂，同时伴随原子位置与位点占有率的非公度调制。实空间键合分析表明，BaGe₆₋ₓ中的缺陷形成与缺陷周围自由电子对的产生相关。当x=0.5时，BaGe₆₋ₓ符合电子精确组成，物理测试结果表明其兼具半导体型电子输运特性与低热导率。