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 contg. stoichiometric lithium niobate nanocrystals embedded in an amorphous silica matrix, the synthesis strategy used to set a new inexpensive sol-gel route to prep. 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 temps. and nanocrystals of several phases were formed. Futhermore, by controlling the gel compns. and the synthesis parameters, it was possible to obtain LiNbO3 as only crystg. phase. LiNbO3-SiO2 nanocomposite thin films on Si-SiO2 and Al2O3 substrates were grown. The LiNbO3 av. size, increasing with the annealing temp., was 27 nm for a film of compn. 10Li2O-10Nb2O5-80SiO2 heated 2 h at 800 °C. Elec. investigation revealed that the nanocrystals size strongly affects the film cond. and the occurrence of hysteretic current-voltage curves.