Synthesis, characterization and oxide conduction in Ba doped apatite-type silicates Ca2La6Bi2(SiO4) 6O2

The apatite-type compounds Ca2-xBaxLa 6Bi2(SiO4)6O2 (0 ≤ x ≤ 2) have been prepared by high temperature solid-state reaction technique. Samples have been investigated by powder X-ray diffraction (XRD), infrared absorption spectroscopy (IR), Raman scattering spectroscopy (Raman) and 29Si MAS-NMR spectroscopy. IR, Raman and NMR techniques have been used to demonstrate the presence of isolated SiO4 groups and to investigate the cation distribution around the silicate tetrahedra. The analysis of 29Si MAS-NMR spectra indicates that Ca and Ba distribution becomes disordered at intermediate compositions. An impedance analysis has been used to analyze the electrical behavior of samples as a function of frequency at different temperatures. Evidences of temperature-dependent electrical relaxation phenomena have been observed. © 2014 Elsevier B.V. All rights reserved.Peer Reviewe