LOW-TEMPERATURE PREPARATION OF NANO-CRYSTALLINE LITHIUM NIOBATE POWDERS BY THE POLYMERIC PRECURSOR METHOD

Lithium niobate powders were synthesized by the polymeric precursor method.The desired metal cations were chelated in an aqueous solution with citric acid(CA) as chelating agent and ethylene glycol(EG) as etherification agent.Homogeneous LiNb precursor solution and gel with no precipitate were achieved with the molar ratios of n(CA)∶n(metal cations)=(3∶1) and n(CA)∶n(EG)=1∶2.The thermal decomposition of the LiNb precursor gels were studied by thermogravimetricdifferential thermal analysis.The phase transformation and the structural variation of LiNbO_3 powders with different calcinating temperatures were studied by Fourier transform infrared spectroscopy and X-ray diffraction.The results reveal that the formation of LiNbO_3 phase takes place via a predominant solid-state reaction between Li_2CO_3 and Nb_2O_5.A pure perovskite-type LiNbO_3 with fine article sizes of 30—50 nm are achieved from LiNb precursor gel calcined at 800 ℃.