Synthesis, crystal structure, relative content of the Mn⁴⁺ ion, tolerance factor and catalytic property of La_1-xCa _xMnO₃ (x = 0.0-1.0)

The series compounds La_1-xCa_xMnO₃ (x = 0.0-1.0) are synthesized by the wet chemical method. When x < 0.5, the crystal structure of La_1-xCa_xMnO₃ belongs to cubic system, when x ≥ 0.5, that of La_1-xCa_xMnO ₃ belongs to orthorhornbic system. The relative contents of the Mn⁴⁺ ion in the series compounds are determined by the chemical analysis methods. The relative content of the Mn⁴⁺ ion in La _1-xCa_xMnO₃ increases gradually with increasing the calcium ion content. When x ≥ 0.5, there is neither the oxygen excess nor the lanthanum deficiency in the compound. The tolerance factor of La _1-xCa_xMnO₃ is calculated and no anomaly in the variation of tolerance factor of La_1-xCa_xMnO₃ with x is found. The catalysis activity of La_1-xCa _xMnO₃ for NO_y reduction by C₃H ₆ varies with x and there is a minimum in the variation of the largest conversion efficiency for NO_y reduction with the composition of La_1-xCa_xMnO₃.