Synthesis, Structural and Thermal Expansion Investigation of La, Ce and Eu Substituted Bi4(SiO4)3

A series of selected rare earth ions substituted bismuth silicates of the chemical formula Bi4-xREx(SiO4)3 (RE = La, Ce and Eu: X = 0.1, 0.2, 0.3) was synthesized by the solution method. Rietveld refinement study revealed that the compounds Bi4(SiO4)3, Bi3.9La0.1(SiO4)3, Bi3.8La0.2(SiO4)3, Bi3.7La0.3(SiO4)3, Bi3.9Ce0.1(SiO4)3 and Bi3.9Eu0.1(SiO4)3 were crystallized in cubic structure with I-43d space group. Scanning electron microscopic images indicated that the larger and rod shaped particles were transformed into smaller and agglomerated ones when the rare earth ions were substituted for Bi ion in the octahedral site. UV-visible diffuse reflectance spectra displayed a shift in absorption edge upon rare earth ion substitution due to the overlapping of s-p transition band with Ln3+-O2- charge transfer band. Bulk thermal expansion of the pure phases was tested using push rod dilatometer. The average coefficients of thermal expansion for Bi4(SiO4)3, Bi3.9La0.1(SiO4)3, Bi3.9Ce0.1(SiO4)3 and Bi3.9Eu0.1(SiO4)3 were found to be 5.19 x 10-6/C, 5.59 x 10- 6/C, 7.10 x 10-6/C and 7.94 x 10-6/C, respectively. The effect of rare earth ionic substitution in thermal expansion behavior was investigated.