Mixed oxides of the [formula omitted] system synthesized by a chemical route: Structural, electric and magnetic characterization

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In this work, ceramic powders of thePr1−xSrxMnO3(PSMO) system, praseodymium manganites doped with strontium in concentrations 0.1≤x≤0.5, were synthesized using the polymeric precursor method (Pechini). The powders obtained were characterized using X-ray diffraction (XRD) and Raman, UV-Vis diffuse reflectance and photoluminescence spectroscopies. Bearing in mind the potential uses of the synthesized PSMO systems, their magnetic and electrical characteristics were determined. Samples heat treated at 900 °C were found to have a single crystalline phase with an orthorhombic perovskite type structure Pnma, a primary particle size of ~32nm and a crystallite size of< 40 nm, a result that would indicate that the primary particles are in fact monocrystals. The Raman spectroscopy results revealed the characteristic vibrations of the synthesized Pr1−xSrxMnO3 mixed oxides and reinforced the fact that for concentrations between 0.1 and 0.5 of strontium, the oxides corresponded to the Pnma space group. Furthermore, the energy gap value varied between 1.61 and 1.51eV and the Urbach energy between 990 and 640meV by increasing the Sr concentration in the manganite. The magnetic characterization meanwhile showed that (Tc) - the ferromagnetic to paramagnetic semiconductor transition temperature - increased as the Sr doping increased, being very close to room temperature, Tc=295K, for a Sr content of x=0.4. The electrical resistivity measurements moreover showed a metal-semiconductor transition, at temperatureTMI−sc, which also gave the highest value for this sample, and which increased when the applied magnetic field increased (TMI−sc = 283 K at 2T). The TC values showed a linear correspondence with temperature TMI−sc, indicating a strong correlation between the magnetic and electrical properties of the Pr1−xSrxMnO3 system samples.