Trapping of different stages of BaTiO(3)reduction with LiH

摘要

We investigated the hydride reduction of tetragonal BaTiO(3)using LiH. The reactions employed molar H : BaTiO(3)ratios of 1.2, 3, and 10 and variable temperatures up to 700 degrees 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(1)H 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 degrees C. The product obtained at 300 degrees C corresponded to oxyhydride BaTiO similar to 2.9H similar to 0.1, whereas reduction at higher temperatures resulted in simultaneous O defect formation, BaTiO2.9-xH0.1 square(x), and eventually - at temperatures above 450 degrees C - to samples void of hydridic H. Concomitantly, the particles of samples reduced at high temperatures (500-600 degrees C) display substantial surface alteration, which is interpreted as the formation of a TiOx(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 (similar to 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 BaTiO(3)with tailored electronic properties.