Synthesis, structure and property studies of a new series of rare earth (Ce, Tb) bismuth silicates

Highlights: • A new series of rare-earth bismuth silicates, LnBiSiO₅(Ln=Ce,Tb), was obtained by flux growth. • LnBiSiO₅ presents a three-dimensional structure composed of zig-zag chains of edge-sharing distorted LnO₈ polyhedra. • Due to the cooperative interaction in TbBiSiO₅ the stronger excited peaks shift towards longer wavelength. A new series of rare earth bismuth silicates has been synthesized by flux method and solid state reaction. LnBiSiO₅ (Ln=Ce, Tb) crystallizes in a triclinic space group P-1 with cell parameters a=5.6763(2) Å, α=105.591(3)° b=6.7922(3) Å, β=110.551(3)° c=6.9593(2) Å, γ=99.733(3)°, Z=2. They exhibit a novel three-dimensional structure consisting of zig-zag chains of edge-sharing Ce/TbO₈ polyhedra that are further linked by SiO₄ units and Bi₂O₈ clusters. The optical band gap (E_g) of TbBiSiO₅ was estimated to be 3.84eV from UV–Vis-IR diffuse reflectance spectra. Photoluminescence measurements suggest that due to the cooperative interaction of Bi and Tb the excitation bands monitored at 544nm are shifted towards longer wavelength which may favor commercial UV diode excitation. The magnetic measurements show that TbBiSiO₅ exhibits paramagnetic behavior without magnetic transitions down to 1.8K.