Sol–gel synthesis of nanocomposite materials based on lithium niobate nanocrystals dispersed in a silica glass matrix

With the final goal to obtain thin films containing stoichiometric lithium niobate nanocrystals embedded in an amorphous silica matrix, the synthesis strategy used to set a new inexpensive sol–gel route to prepare nanocomposite materials in the Li2O–Nb2O5–SiO2 system is reported. In this route, LiNO3, NbCl5 and Si(OC2H5)4 were used as starting materials. The gels were annealed at different temperatures and nanocrystals of several phases were formed. Futhermore, by controlling the gel compositions and the synthesis parameters, it was possible to obtain LiNbO3 as only crystallizing phase. LiNbO3–SiO2 nanocomposite thin films on Si–SiO2 and Al2O3 substrates were grown. The LiNbO3 average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li2O–10Nb2O5–80SiO2 heated 2 h at 800 °C. Electrical investigation revealed that the nanocrystals size strongly affects the film conductivity and the occurrence of hysteretic current–voltage curves.