Feifei Zheng

Formation mechanism of black LiTaO3 single crystals through chemical reduction

Lithium tantalate (LiTaO3, LT) wafers of different colors were prepared through chemical reduction of regular congruent LT wafers. Samples with different colors corresponding to different annealing temperatures were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and measurements of the Curie temperature and density. It was found that chemical reduction does not influence the basic LT structure. The Ta charge state change due to chemical reduction was found to be the main reason for the formation of black LT wafers.

Spray drying mass-production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder based on a wet-chemical method

A mass production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder was proposed based on a wet-chemical method/spray drying process. A stable homogenous precursor solution was prepared by dissolving commercial Nb(OH)5, Li2CO3 and MgO, and was stabilized with citric acid (CA) as a chelating agent. Spherical Mg:LN precursor powder can be obtained by a spray-drying method, and spherical mono-phase perovskite Mg:LN polycrystalline powder with uniform size was obtained by calcining the precursor powder at relatively low temperature. Thermogravimetry–differential thermal analysis (TG–DTA), X-ray diffraction (XRD), infrared spectroscopy and scanning electron microscopy (SEM) were used to characterize the precursor and product powder. The as-obtained Mg:LN powder was used for Mg:LN single-crystal growth. The obtained Mg:LN single crystal possesses both high optical homogeneity and ingredient uniformity. This mass production route for preparation of Mg:LN powder provides a solution to the problem of defects in Mg:LN single crystals caused by nonhomogeneity of magnesium distribution.

111) Twinned BaTiO3 microcrystallites

We report here the controlled synthesis of (111) twinned BaTiO3 microcrystallites, which are widely known for their (110) ferroelectric twins. This (111) twinned structure was obtained through a composite hydroxide mediated process by using amorphous TiO2 powders. A twin assisted re-entrant growth model is proposed to account for the microstructural aspects determined. It is considered that the (111) twins originate from the Ti–O octahedra of the amorphous TiO2 powders. The role of oriented aggregation is also discussed.