We investigated the hydride reduction of tetragonal BaTiO₃ using LiH. The reactions employed molar H : BaTiO₃ ratios of 1.2, 3, and 10 and variable temperatures up to 700 °C. The air-stable reduced products were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, thermogravimetric analysis (TGA), X-ray fluorescence (XRF), and ¹H magic-angle spinning (MAS) NMR spectroscopy. Effective reduction, as indicated by the formation of dark blue to black colored, cubic-phased, products was observed at temperatures as low as 300 °C. The product obtained at 300 °C corresponded to oxyhydride BaTiO_∼2.9H_∼0.1, whereas reduction at higher temperatures resulted in simultaneous O defect formation, BaTiO_2.9−xH_0.1□_x, and eventually – at temperatures above 450 °C – to samples void of hydridic H. Concomitantly, the particles of samples reduced at high temperatures (500–600 °C) display substantial surface alteration, which is interpreted as the formation of a TiO_x(OH)_y shell, and sintering. Diffuse reflectance UV-VIS spectroscopy shows broad absorption in the VIS-NIR region, which is indicative of the presence of n-type free charge carriers. The size of the intrinsic band gap (∼3.2 eV) appears only slightly altered. Mott–Schottky measurements confirm the n-type conductivity and reveal shifts of the conduction band edge in the LiH reduced samples. Thus LiH appears as a versatile reagent to produce various distinct forms of reduced BaTiO₃ with tailored electronic properties.

中文翻译：

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用 LiH 捕获不同阶段的 BaTiO3 还原

我们研究了使用 LiH对四方 BaTiO _{3的氢化物还原。}该反应采用 H ∶ BaTiO ₃摩尔比为 1.2、3 和 10 以及高达 700 °C 的可变温度。通过粉末 X 射线衍射 (PXRD)、扫描电子显微镜、热重分析 (TGA)、X 射线荧光 (XRF) 和¹ H 魔角旋转 (MAS) NMR 光谱对空气稳定的还原产物进行了表征。在低至 300 °C 的温度下观察到有效还原，如深蓝色至黑色立方相产物的形成所示。在 300 °C 下得到的产物对应于氢化物 BaTiO _∼2.9 H _∼0.1，而在较高温度下的还原导致同时形成 O 缺陷，BaTiO _{2.9− x} H _0.1 □ _x，并最终在 450 °C 以上的温度下生成没有氢化 H 的样品。同时，样品的颗粒在高温下还原（ 500–600 °C）显示出明显的表面变化，这被解释为形成 TiO _x (OH) _y壳和烧结。漫反射 UV-VIS 光谱在 VIS-NIR 区域显示出广泛的吸收，这表明存在 n 型自由电荷载流子。固有带隙的大小（~3.2 eV）似乎只有轻微的改变。Mott-Schottky 测量证实了 n 型电导率，并揭示了 LiH 还原样品中导带边缘的变化。因此，LiH 似乎是一种通用试剂，可生产各种不同形式的具有定制电子特性的还原 BaTiO _{3 。}