Synthesis and characterization of rare-earth doped SrBi₂Nb₂O₉ phase in lithium borate based nanocrystallized glasses

Glass composites comprising of un-doped and samarium-doped SrBi₂Nb₂O₉ nanocrystallites are fabricated in the glass system 16.66SrO-16.66[(1-x)Bi₂O₃-xSm₂O₃]-16.66Nb₂O₅-50Li₂B₄O₇ (0≤x≤0.5, in mol%) via the melt quenching technique. The glassy nature of the as-quenched samples is established by differential thermal analyses. Transmission electron microscopic studies reveal the presence of about 15 nm sized spherical crystallites of the fluorite-like SrBi_1.9Sm_0.1Nb₂O₉ phase in the samples heat treated at 530 °C. The formation of layered perovskite-type un-doped and samarium-doped SrBi₂Nb₂O₉ nanocrystallites with an orthorhombic structure through the intermediate fluorite phase is confirmed by X-ray powder diffraction and micro-Raman spectroscopic studies. The influence of samarium doping on the lattice parameters, lattice distortions, and the Raman peak positions of SrBi₂Nb₂O₉ perovskite phase is clarified. The dielectric constants of the perovskite SrBi₂Nb₂O₉ and SrBi_1.9Sm_0.1Nb₂O₉ nanocrystals are relatively larger than those of the corresponding fluorite-like phase and the precursor glass.