New glasses of 16.66SrO-16.66[(1-x)Bi2O3-xSm(2)O(3)]-16.66Nb(2)O(5)-50Li(2)B(4)O(7) (0 <= x <= 0.5, in molar ratio), i.e., the pseudo-binary Sm2O3-doped SrBi2Nb2O9-Li2B4O7 glass system, giving the crystallization of Sm3+-doped SrBi2Nb2O9 nanocrystals are developed. It is found that the thermal stability of the glasses against the crystallization and the optical band gap energy increases with increasing Sm2O3 content. The formation of fluorite-type Sm3+-doped SrBi2Nb2O9 nanocrystals (diameters: 13-37 nm) with a cubic structure is confirmed in the crystallized (530 degrees C, 3 h) samples from X-ray powder diffraction analyses, Raman scattering spectrum measurements, and transmission electron microscope observations. The effect of Sm3+-doping on the microstructure, Raman scattering peak positions, and dielectric properties of composites comprising of fluorite-type SrBi2Nb2O9 nanocrystals and the Li2B4O7 glassy phase is clarified. It is found that fluorite-type SrBi2Nb2O9 nanocrystals transform to stable perovskite-type SrBi2Nb2O9 crystals with an orthorhombic structure by heat treatments at around 630 degrees C. (c) 2009 Elsevier B.V. All rights reserved.