Structural, electrical and magnetic characterization of nanoparticles of the Pr1-xSrxCoO3 (0.1≤ x ≤ 0.5) system synthesized by a chemical route

Abstract

Ceramic powders of the strontium-doped praseodymium cobaltite system, Pr_1-xSr_xCoO₃ - PSCO, were synthesized in concentrations (0.1≤ x ≤ 0.5), using the Pechini polymeric precursor method. The synthesized powders, heat treated at 1000 °C, had a single crystalline phase with an orthorhombic perovskite type Pnma structure and a primary particle size <100 nm, a characteristic determined using SEM and TEM techniques. The results of Raman spectroscopy allowed us to determine the distortions in the lattice vibrations caused by the ions that replace the A sites (Pr for Sr). The PSCO samples with concentrations between x = 0.2 and x = 0.5, had energy gap values of ∼3.3 eV, while for the concentration x = 0.1 a value close to 4 eV was obtained. In addition, the indirect gap calculations, carried out for all samples, showed a value close to 2.5 eV. These results suggest that the substitution of the corresponding transition metal ion allowed the modification of the gap energy, obtaining wide-gap semiconductors. The magnetic characterization showed that T_c - the temperature of transition from the PM to the FM state - increased for the concentration of x = 0.4 of strontium, being very close to room temperature (T_c = 290 K). In addition, a second anomalous magnetic transition was observed at T_A = 115 K for the PSCO (x = 0.5) sample, behavior that has also been reported by other researchers.