Nitish Kumar Singh

Electrical conductivity of undoped, singly doped, and co-doped ceria

In order to investigate the effect of single doping and co-doping on the enhancement of ionic conductivity in ceria (CeO2), CeO2 and a few compositions in the system Ce0.85Sm0.15 − xGdxO1.925 (x = 0.00, 0.06, 0.09, and 0.15) were prepared using citrate–nitrate auto-combustion method. Gels were characterized by simultaneous differential thermal analysis and thermogravimetric analysis to confirm the formation of end product from the precursor. All the compositions were found to be single-phase solid solution from their X-ray diffraction pattern. Complex plane impedance analysis clearly revealed the contribution of grains, grain boundaries, and electrode specimen interface to the total value of the resistance. The value of activation energy, Ea, of conduction shows that the conduction process is mainly due to diffusion of O2− ions through oxygen vacancies. Effect of doping has been analyzed using the concept of radius mismatch and effective index reported earlier in the literature.

Study of ion dynamics in lanthanum aluminate probed by conductivity spectroscopy

Ion conducting lanthanum aluminate, LaAlO3 was synthesized via a citrate nitrate auto combustion route. Phase formation of LaAlO3 was studied by thermal and powder X-ray diffraction techniques. The conductivity spectra of LaAlO3 were investigated in the frequency range 20 Hz to 1 MHz at different temperatures. The conductivity data were analyzed in terms of Jonschers power law. The dc conductivity and hopping frequency of the charge carrier were extracted from the analysis of conductivity spectra. The corresponding value of activation energy implies that the conductivity is mainly dependent on the mobility of the charge carriers. The conductivity spectra were scaled according to Ghosh scaling. Moreover, the modulus spectra were also scaled. Both the scaling behaviours reflected the temperature independent conduction mechanism in the system.

Effect of lanthanum (La3+) doping on the structural and electrical properties of double perovskite Sr2NiMoO6

To study the effect of La3+ doping on structural and electrical properties, a few compositions of the system Sr2−xLaxNiMoO6−δ (x = 0.02, 0.04, 0.06, 0.08, and 0.10) were synthesized via the citrate–nitrate route. Thermally activated electrical conductivity was observed in this system. The reduction of Mo6+ to Mo5+ was confirmed not only in the thermal analysis but also in the detailed XPS investigation of the samples. The structural behavior was probed by phase formation of the compositions confirmed in X-ray diffraction Rietveld analysis. The SEM images of the compositions indicated that a grain size of the order of a few micrometers was observed in this system. The highest conductivity was obtained for the composition with x = 0.04. The electrical behaviour of the system was explained in terms of the lattice strain, the impure phase present in the system and also in terms of the enhanced charge density . The XPS and XRD analysis support the variation of conductivity behaviour with composition.