Structure studies of La1.85Sr0.15CuO4 doped with mg at high doping level

Ceramic cuprates of La_1.85Sr_0.15Cu_1-yMg_yO₄ with 0.00≤y≤0.30 are synthesized. The resistivity dependence of temperature is obtained up to room temperature. The metal-insulator transition at the range of higher doping level (y> 0.10) is observed. There is no impurity phase detected in the entire Mg-doped region. The structure of these Mg-doped samples is characterized by X-ray diffraction studies. The atomic structural parameters are obtained by Rietveld refinements for the Mg-doped samples with y≤0.30. No phase transition is detected within the accuracy of our experiments. The Mg doping reduce the local Jahn-Teller distortion of the CuO₆ octahedra. Some meaningful bond distances are determined according to the refined results. According to the variations of the lattice parameters with y, the whole doping range could be divided into two regions: low doping level (LDL) and high doping level (HDL). The bond length between the two apical oxygen atoms in the CuO₆ octahedra for the Mg-doped samples increases with increasing content of Mg in the LDL, and high doping level (HDL). The bond length between the two apical oxygen atoms in the CuO₆ octahedra for the Mg-doped samples increases with increasing content of Mg in the LDL, and decreases in the HDL.