Lithium niobate thin films have been deposited on Pt/Ti/SiO2/Si(100) substrates by Pechini method. Characterization of the initial precursor solutions containing citric acid (CA), niobium and lithium ions has been performed by Fourier transform infrared spectroscopy, Raman spectroscopy and carbon nuclear magnetic resonance spectroscopy. The results indicate that citric acid coordinate to niobium ions to form a niobium–CA complex through one terminal carboxyl group, the hydroxyl group and the central carboxyl group as a tridentate ligand. The thermal decomposition of the Li–Nb precursors gel powder has been studied and the results show that LiNbO3 phase is formed directly from the thermal decomposition of the precursor gel. By heat-treatment at 600℃for 2h, polycrystalline LiNbO3 thin films with smooth and crack-free surface could be achieved.

Sr0.5Ba0.5Nb2O6 (SBN50) thin films have been prepared using aqueous organic gel method. The differences in the decomposition between Sr–Ba–Nb nitrate precursor solutions with different pH values were investigate. By heat treatment at 700℃ for 2h, SBN thin films with smooth and crack-free surface were derived from the precursor solution of a lower pH=8.XRD patterns revealed the polycrystalline nature of the SBN thin films on Pt/Ti/SiO2/Si(100) substrates. Electric properties measurement indicated that the SBN films demonstrated a ferroelectric hysteresis loop. The remanent polarization (Pr) and coercive field (Ec) were 8.17 µC/cm2 and 16.9 kV/cm, respectively.

Potassium lithium niobate (KLN) ceramic powders with low Li content have been synthesized by using the Pechini method. The composition of the powder can be written as K2.95Li1.38Nb6.22O17, which contains relatively fewer Li ions than K3Li2Nb5O15 powder. The thermal decomposition of the precursor gel has been studied by TG–DTA and the products calcined at different temperatures have been characterized by XRD and TEM. It is concluded that the K2.95Li1.38Nb6.22O17 powders, about 50 nm sized and uniformly shaped, are obtained through the calcination of the precursor gel at 900 8C for 2 h. The difference between the powder composition and starting composition is caused by the volatile loss of the lithium during high-temperature heat treatment. The control of pH value and the molar ratio of citric acid/ metal cations of the precursor solution is important to obtain clear K–Li–Nb precursor solution and gel.

SrxBa1−xNb2O6 (x=0.4, 0.5, 0.6) ceramic powders have been synthesized by using the aqueous organic gel routes. The desired metal cations are chelated in a solution using citric acid and ethylenediaminetertraacetic acid (EDTA) as the chelating agents. The thermal decompostion of the metal carboxylate precursors gels have been studied by TG/DTA and the products derived from calcinations of the gels at different temperatures have been characterized by XRD and TEM. The results reveal that tetragonal tungsten-bronze-type SBN with fine particle size could be achieved at 800℃. The pH 8 used during the preparation of Sr-Ba-Nb precursor gels is determined by calculation of the conditional formation constants Kcf of Sr-EDTA and Ba-EDTA complexes. The influences of the pH and the molar ratio of citric acid:Nb cation on the formation of homogeneous Sr-Ba-Nb precursor gels are also studied.