Preparation of nanocrystalline lithium niobate powders at low temperature

摘要

A facile route to prepare lithium niobate (LiNbO_3) powders was proposed by an alternative solid-state method. Stoichiometric Li _2C_2O_4 and ammonium niobium oxalate were mixed with small amounts of water and then dried at room temperature. It was demonstrated that Li[NbO(C_2O_4)_2]·nH _2O intermediate was produced by an ion-exchange reaction. Pure LiNbO_3 powders were successfully synthesized by heating the intermediate at 500, 600 and 700 °C for 3 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, UV-Vis diffuse reflectance (UV-Vis) spectroscopy and thermogravimetric (TG) analysis were used to characterize the precursor compound and as-prepared samples. XRD results reveal that all the products are identified as hexagonal structure with high relative crystallinity (>87%). The particle size is found to be about 40 nm for the mixture calcined at 500 °C according to XRD data, which is in good agreement with SEM data. The as-prepared LiNbO_3 powders by this method are high quality according to FTIR spectra. (Li_(0.996)Nb_(0.005))Nb_(0.999)O _3 phase was formed when the calcination temperature was raised to 800 °C.