Synthesis of LiNbO3 Nanoparticles by Citrate Gel Method

We present investigations on the preparation of nearly stoichiometric lithium niobate (LiNbO3) nanoparticles using citrate gel method. Citric acid is used as a chelating agent and ethylene glycol is added for polyestarification between the chelates. In addition to the main lithium niobate phase, the secondary phase of lithium niobate, LiNb3O8, and an unreacted phase of Nb2O5 were also observed in the resultant product. The appearance of unwanted phases is a serious problem in citrate gel method. We have observed that the synthesis parameters such as molar ratio of citric acid to metal ions (R1), pH, molar ratio of ethylene glycol to citric acid (R2) and calcination temperature strongly influence the presence of the unwanted phases and these parameters are optimized to remove these phases. Evolution of the phase was investigated by powder XRD whereas TG/DTA was done to find out the crystallization temperature. It was observed that nearly stoichiometric and pure LiNbO3 nanoparticles can be obtained with the optimized parameters, R1 = 3, pH = 8, R2 ≥ 2 and calcination temperature = 700 degrees C. The stoichiometry of the synthesized LiNbO3 nanoparticles was investigated using Raman spectroscopy.