V. Prashanth Kumar

Crystal structure, electrical conductivity and thermal expansion of Nd1–xCaxCoO3–δ (0≤x≤0·5)

Abstract The synthesis, crystal structure, thermal expansion and electrical conductivity of the ceramic oxide materials (Nd1–xCax)CoO3 (0≤x≤0·5) were investigated. These powders with perovskites structure were synthesized using the sol–gel method. Compositions have a pure orthorhombic structure up to 0·3 Ca doping. The lattice parameters were determined at room temperature (RT) by powder X-ray diffraction. Thermal expansion measurements on the sintered samples were carried out from RT to 900°C. The average linear thermal expansion coefficient range was found to decrease with increasing Ca doping up to x=0·4 and thereafter it increased. The thermal expansion curves for all values of x displayed rapid increase in slope at high temperatures. Electrical DC conductivity measurements were taken from RT to 600°C. The conductivity of the samples increased with Ca concentration up to 0·3.

Characterization and thermal expansion of Sr2Fe1-xInxMoO6 (x=0.0, 0.1 and 0.4 wt. %) double perovskites

Double perovskite oxides of Sr2Fe1-xInxMoO6 (x = 0.0, 0.1 and 0.4 wt. %.) were prepared by sol-gel growth followed by annealing under reducing atmosphere conditions of 10% H2/Ar flow. These samples were characterized by X-ray diffraction, Scanning Electron Microscopy and Electron Spin Resonance studies. High temperature thermal expansion studies were carried out using Netzsch 402PC dilatometer in the temperature range from 40 to 400°C. The coefficient of thermal expansion (α) was calculated at different temperature for all the samples. The value of α was found to increase with increase of temperature while average value of coefficient of thermal expansion found to decrease with indium composition in SFIMO materials.

The effect of Pr co-dopant in samarium doped ceria

The compositions of Ce0.8−xSm0.2PrxO2−δ (x=0, 0.02, 0.04, 0.06) were prepared through the sol-gel route. The effect of Pr addition on the crystal structure, densification and thermal expansion of Ce0.8Sm0.2O2−δ was studied. The powder X-ray diffraction (XRD) analysis showed that all the samples exhibit a fluorite structure. The lattice parameters and volume of the unit cell increase with Pr doping. Density of all the samples is more than 90% of theoretical density. The thermal expansion was measured using dilatometric technique in the temperature range 30-1000°C and it was observed that the thermal expansion increased linearly with increasing temperature for all the samples.

CRYSTAL STRUCTURE, ELECTRICAL CONDUCTIVITY AND THERMAL EXPANSION OF Pr1-xSrxFeO3-δ(0 ≤ x ≤ 0.6)

The crystal structure at room temperature (RT), thermal expansion from RT to 1000°C and electrical conductivity, from RT to 600°C, of the perovskite-type oxides in the system Pr1-xSrxFeO3(x = 0, 0.2, 0.4, 0.6) were studied. All the compounds have the orthorhombic perovskite GdFeO3-type structure with space group Pbnm. The lattice parameters were determined by X-ray powder diffraction. The Pseudo cubic lattice parameter decreases with an increase in x, while the coefficient of linear thermal expansion increases. The thermal expansion is almost linear for x = 0 and 0.2. The electrical conductivity increases with increasing x while the activation energy decreases. The electrical conductivity can be described by the small polaron hopping conductivity model.