Synthesis, X-ray, magnetic and electrical studies of substituted (Pr, Sr)MnO3 perovskites

A systematic study of the structural, magnetic and electrical properties of the manganites Pr1-xSrxMnO3 (0 less than or equal to x less than or equal to 0.5) has been carried out. X-ray diffraction investigation shows a struc tural change with composition, from orthorhombic (0 less than or equal to x less than or equal to 0.2) to rhombohedral (0.25 less than or equal to x l ess than or equal to 0.5). The magnetic properties of Pr1-xSrxMnO3 samples could be explained on the basis of a double exchange mechanism between pair s of Mn3+ and Mn4+ ions. These properties are strongly dependent on the rat io of Mn3+/Mn4+. The maximum of the ferromagnetic transition temperature T- c is reached at x approximate to 0.35 corresponding to a value 1.85 of this ratio. The investigation of the electrical properties shows a semiconducto r to metal transition as a function of temperature (0.25 less than or equal to x less than or equal to 0.4) with a metallic-like behaviour above a cri tical temperature T-p. A semiconducting-like one is observed for all the ra nge of temperature (50 300 K) for (0 less than or equal to x less than or e qual to 0.2 and x = 0.5). The evolution of activated energies with the carr ier concentration has been investigated.