Crystal structure, composition and valence state of cations in mixed-valence A1-xCdxMnO3 (A=Pr, La) ceramics

Complex manganites A_1−xCd_xMnO₃ (A = Pr, La) are synthesized by solid state reaction method. X-ray diffraction, scanning electron microscopy and energy-dispersive analysis are applied to study their crystal structure, surface morphology, elemental and phase composition. X-ray photoelectron spectroscopy (XPS) methods are used to study the charge states of Pr and La cations, as well as to quantify the fractions of coexisting Mn³⁺ and Mn⁴⁺ ions. La3d-, La4d-, Pr4d- и Mn2p-spectra of La³⁺, Pr³⁺, Mn³⁺ and Mn⁴⁺ ions are calculated in the isolated–ion approximation with accounting for multiplet splitting and charge transfer effect. Good agreement with the experiment is obtained. The relative fractions of trivalent and tetravalent manganese ions in La_0.45Cd_0.78Mn_0,9O_2.86 and Pr_0.50Cd_0.76Mn_0.86O_2.88 samples are determined by fitting the Mn2p spectra by superposition of experimental spectra containing only Mn³⁺, and only Mn⁴⁺ ions; they were found to be 0.71Mn³⁺/0.29Mn⁴⁺ and 0.54Mn³⁺/0.46Mn⁴⁺, respectively.