High temperature thermal expansion and electrical conductivity of Ln0.95MnO3+δ (Ln = La, Nd or Gd)

The rare earth deficient manganites Ln0.95MnO3+delta (Ln=La, Nd or Gd) have been prepared by conventional ceramic method as well as by wet chemical methods like nitrate route and sol-gel route. Structural transformation, thermal expansion and electrical conductivity at elevated temperature were investigated on Ln0.95MnO3+delta. The X-ray diffraction studies revealed that crystal symmetry of all the rare earth deficient manganites prepared either by sol-gel or solid-state route showed orthorhombic symmetry except lanthanum manganite prepared by solid-state route and the nitrate route. The thermal expansion behavior was studied using thermo-dilatometry and high temperature XRD techniques. The electrical conductivity studies of Ln0.95MnO3+delta showed a clear phase transformation in case of La0.95MnO3+delta synthesized by solid state route which was missing in all other rare earth manganites prepared by solid state and nitrate routes and wet chemical method. A comparative study on their linear thermal expansion behavior indicates that the value of coefficient of thermal expansion (alpha) reduces to half as it goes from La to Gd. The electrical conductivity of sample synthesized by nitrate route was more as compared to sample prepared by other route like ceramic or sol-gel.