探討高性能碲化鍺熱電材料的穩態結構：通過熱循環和高壓技術破壞鐵電晶疇結構

Exploring the steady-state crystal structure of high thermoelectric performance GeTe: Disrupting the ferroelectric domain structure via thermocycling and high-pressure methods

李郁儒(Yu-Ju Lee)；龔慧貞(Jennifer Kung)；魏百駿(Pai-Chun Wei)

熱電材料 ； 碲化鍺化合物 ； 晶疇結構 ； 低對稱性 ； 高壓合成技術 ； Thermoelectric materials ； Germanium telluride ； X-ray diffraction ； High pressure synthesis

真空科技

37卷2期（2024 / 06 / 30）

28~1 - 28~9

繁體中文;英文

GeTe是目前熱電轉換效率最優異的中高溫熱電材料，然而其在700 K附近具有一3-3的鐵電相變。在此研究中我們首先發現Ge_(50)Te_(50)粉末在的熱循環試驗中，經過多次反覆升降溫之後其主要化學成分逐漸轉變為Ge_(49)Te_(51)，其原始的魚骨狀晶疇結構也遭到破壞，此結果表明GeTe真正的穩態晶體結構為Ge_(49)Te_(51)。此外，利用高壓合成技術，我們成功地利用大體積壓力機合成純相Ge_(49)Te_(51)，值得注意的是，Ge_(49)Te_(51)結構在低溫與高溫區的空間群仍為3及3，然而卻可以發現Ge_(49)Te_(51)3相的X光繞射峰的半高寬明顯變寬，暗示其晶格內原子排列的扭曲。

GeTe is currently the most efficient thermoelectric material for medium to high-temperature thermoelectric conversion. However, it undergoes a ferroelectric phase transition from 3 to 3 around 700 K. In this investigation, we observed that during thermal cycling tests of Ge_(50)Te_(50) powder, the chemical composition shifted gradually towards Ge_(49)Te_(51), coinciding with the disappearance of the herringbone domain structure. This finding suggests that the stable crystal structure and chemical composition of GeTe correspond to Ge_(49)Te_(51). We further demonstrate that under 10 GPa, Ge_(49)Te_(51) adopt a purely rhombohedral phase. However, the diffraction peaks of Ge_(49)Te_(51) are notably broadened, indicating additional atomic distortion within the lattice.