Structure and electrical properties of Ln2(MO4)3(Ln = La or Sm; M = W or Mo) nanoceramics

Abstract

Ln₂(MO₄)₃ (Ln = La and Sm; M = W and Mo) nanomaterials are synthesized by auto ignited combustion method. The synthesized materials are characterized by X-ray diffraction, vibrational spectroscopy, transmission electron microscopy, scanning electron microscopy and impedance spectroscopy. The structural analysis established monoclinic structure for the synthesised nanoparticles. The average crystallite size estimated using Debye–Scherrer formula is obtained in the range 27 to 35 nm. Raman and FTIR studies revealed two types of WO₄ and MoO₄ tetrahedrons in tungstate and molybdate compounds, respectively. TEM micrographs show that the nanoparticles are spherical in shape with narrow size distribution. SEM micrographs of bulk ceramics showed high densification, low porosity and grain distribution of distinct dimensions. EDS analysis confirmed the chemical composition of the materials and agreed with their actual stoichiometry. The presence of grain, grain boundary and electrode contribution to impedance spectra of bulk ceramics was analysed using complex impedance plot. Arrhenius plots of all the prepared materials show almost a linear behaviour with a small deviation noticed at particular temperatures. The conductivity studies of prepared materials showed oxide ion and mixed electron-proton conduction.