Electrical conductivity studies of nanocrystalline lanthanum silicate synthesized by sol–gel route

Nanocrystalline apatite type structured lanthanum silicate (La10Si6O27) sample was synthesized by sol–gel process. Thermal behavior of the dried gel of lanthanum silicate sample was studied using TG/DTA. The structural coordination of the dried gel of lanthanum silicate, calcined at various temperatures, was identified from the observed FTIR spectral results. The observed XRD patterns of the calcined dried gel were compared with the ICDD data and confirmed the formation of crystalline lanthanum silicate phase. The average crystalline size of La10Si6O27 was calculated using the Scherrer formula and it is found to be ∼80 nm. The observed SEM images of the lanthanum silicate indicate the formation of the spherical particles and the existence of O, Si and La in the lanthanum silicate are confirmed from the SEM-EDX spectrum. The grain and grain boundary conductivities are evaluated by analyzing the measured impedance data, using winfit software, obtained at different temperatures, of La10Si6O27 sample. Also, the observed grain and grain boundary conductivity behaviors of the La10Si6O27 sample are analysed using brick layer model. The electrical permittivity and electrical modulus were calculated from the measured impedance data and were analyzed by fitting through the Havriliak and Negami function to describe the dielectric relaxation behavior of the nanocrystalline lanthanum silicate.

Research highlights▶ Nanocrystalline La10Si6O27 material was synthesized by sol–gel method. ▶ TG/DTA curves predicted the thermal behavior of the material. ▶ FTIR spectra confirmed the formation of SiO4 and La–O network in the La10Si6O27. ▶ XRD patterns confirmed the formation of pure crystalline La10Si6O27 phase. ▶ The grain interior and the grain boundary conductivities are evaluated.