Effect of sintering temperature on the structure and transport properties of La4/3Sr5/3Mn2O7

La4/3Sr5/3Mn2O7 polycrystalline samples are prepared by the sol-gel method followed by sintering treatments at various temperatures (T s). The sample sintered at lower T s has higher insulator-metal transition temperature (T p). But for the case of higher T s, the sample has higher T p and lower resistivity at the layer near the surface, but lower T p and larger resistivity inside the sample. Based on the structure analysis, we propose that although a higher T s favors the formation of Sr3Ti2O7 phase, it is likely for the segregation of (La, Sr)MnO3 phase to the surface layer, resulting in a higher T p and lower resistivity at the layer near the surface