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

Abstract

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 Li 2O–Nb 2O 5–SiO 2 system is reported. In this route, LiNO 3, NbCl 5 and Si(OC 2H 5) 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 LiNbO 3 as only crystallizing phase. LiNbO 3–SiO 2 nanocomposite thin films on Si–SiO 2 and Al 2O 3 substrates were grown. The LiNbO 3 average size, increasing with the annealing temperature, was 27 nm for a film of composition 10Li 2O–10Nb 2O 5–80SiO 2 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.