Ga₂O₃ is an ultra-wide-bandgap semiconductor that is receiving considerable attention due to its promising applications in high-frequency, high-power and high-temperature settings. It can be prepared by calcinating the α-GaOOH phase at high temperatures. Understanding the significance of hydroxyl groups in α-GaOOH, dehydroxylation and the structural transition at high temperatures has become a key aspect of preparing high-quality α-Ga₂O₃ crystals, but the underlying mechanism remains unknown. In this research, α-GaOOH nanorods were hydrothermally synthesized and the structural evolution of α-GaOOH investigated at high temperatures by in situ X-ray diffraction. The hydroxyl group in α-GaOOH squeezes Ga³⁺ from the center of the [GaO₆] octahedron, resulting in deformed [GaO₆] octahedra and significant microstrain in α-GaOOH. The hydroxyl groups are peeled off from α-GaOOH when the temperature exceeds 200°C, resulting in contraction along the c-axis direction and expansion along the a-axis direction of α-GaOOH. When the temperature exceeds 300°C, the Ga—O bond inside the double chains preferentially breaks to generate square-wave-like octahedron chains, and the neighboring chains repack to form hexagonal-like octahedron layers. The octahedron layers are packed up and down by electrostatic interaction to generate the α-Ga₂O₃ structure. This work highlights the role of hydroxyl groups in α-GaOOH, dehydroxylation and the structural transition on the atomic scale, providing valuable guidelines for the fabrication of high-quality α-Ga₂O₃ crystals.

中文翻译：

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原位 X 射线衍射研究 α-GaOOH 的脱羟基和结构转变

Ga ₂ O ₃是一种超宽带隙半导体，因其在高频、高功率和高温环境中的良好应用而受到广泛关注。它可以通过高温煅烧α-GaOOH相来制备。了解羟基在α-GaOOH、脱羟基和高温结构转变中的重要性已成为制备高质量α-Ga ₂ O ₃晶体的关键方面，但其潜在机制仍不清楚。在本研究中，采用水热法合成了α-GaOOH纳米棒，并通过原位X射线衍射研究了α-GaOOH在高温下的结构演化。 α-GaOOH中的羟基将Ga ^3+从[GaO ₆ ]八面体的中心挤压，导致[GaO ₆ ]八面体变形并在α-GaOOH中产生显着的微应变。当温度超过200℃时，羟基从α-GaOOH上剥离，导致α-GaOOH沿c轴方向收缩并沿a轴方向膨胀。当温度超过300℃时，双链内部的Ga-O键优先断裂，生成方波状八面体链，相邻链重新堆积形成六角形八面体层。八面体层通过静电相互作用上下堆积，形成α-Ga ₂ O ₃结构。这项工作强调了羟基在α-GaOOH、脱羟基和原子尺度结构转变中的作用，为高质量α-Ga ₂ O ₃晶体的制造提供了有价值的指导。