Crystallite size effect on the structural, microstructure, magnetic and electrical transport properties of Pr0.7Sr0.3Mn0.9Cr0.1O3 nanocrystalline via a modified Pechini method

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• Fine particles samples of Pr0.7Sr0.3Mn0.90Cr0.1O3 were prepared using Pechini method.
• The lattices parameters and the unit cell volume increase with the increase of crystallite size.
• Nanocrystalline samples of Pr0.7Sr0.3Mn0.90Cr0.1O3 crystallize in the orthorhombic structure.
• The lattices parameters and the unit cell volume increase with the increase of crystallite size.
• The resistivity is described in terms of percolation phase in the whole range of temperatures.

The effect of nanometric crystallite size on the structural, microstructure, magnetic and electrical transport properties of single phase, nanocrystalline, granular Pr0.7Sr0.3Mn0.90Cr0.1O3 is investigated. The materials were synthesized using a soft chemical method (Pechini method) by sintering at three different temperatures 1123, 1223 and 1323 K to produce samples of crystallites sizes 32 nm, 40 nm, and 46 nm. X-ray diffraction studies confirm that, phase formation starts at 1123 K. All samples crystallize with the orthorhombic symmetry within the space group Pnma. SEM micrographs of the samples revealed that the grain size increase and the porosity decrease with the increase in sintering temperature. All samples undergo a paramagnetic (PM) – ferromagnetic (FM) phase transition at T = TC. Furthermore, a reduction in magnetization and a slight decrease in Curie temperature TC have been observed as the sintering temperature decreases. The metal–semiconductor transition, TM-Sc increased linearly from 131 K to 181 K with the increase in sintering temperature. Additionally, the resistivity obviously increases with decreasing grain size mainly due to the increase of both the height and width of tunnelling barriers with decreasing grain size. Based on the idea that doped manganites consist of ferromagnetic-metallic and paramagnetic-semiconducting regions coexisting in the same specimen, a good fit of the resistivity with the phenomenological percolation model, may be obtained by combining the contributions of the resistivity above and below TM-Sc by a single expression in the temperature region between 70 and 300 K. We found that the estimated results are in good agreement with the obtained experimental data.