Structural, electrical and thermoelectric property of electron beam irradiated La_0.8Sr_0.2MnO₃ manganites

In this work, we are reporting the effect of electron beam irradiation on the electrical and thermoelectric properties of La_0.8Sr_0.2MnO₃ manganites. Polycrystalline La_0.8Sr_0.2MnO₃ samples were prepared by conventional solid state reaction method. The stoichiometric amount of constituent materials were taken and grounded for several hours. Then the mixture was calcined with intermediate grinding to ensure that the mixture is homogeneous. After calcination the powder was pressurized into pellets and sintered. Then the pelletized samples were irradiated by electron beam using an 8 MeV electron accelerator. The crystallographic phase identification of synthesized samples was carried out by X-ray diffraction. Then the electrical resistivity and thermoelectric power measurements were performed for the pristine and irradiated samples. It is observed that the lattice volume increases with increase in dosage of e-beam. With irradiation an increase in resistivity is observed. For small irradiation dosage, we first observe a decrease in metal-insulator transition temperature TMI; thereafter TMI increases with further increase in dosage of irradiation. Both, the resistivity data and thermo-electric power data demonstrate that small polaron hopping model is valid in low temperature region. (author)