Powder X-ray diffraction and Rietveld analysis of La_(1-x)Ca_xMnO_3(0 < X < 1)

摘要

Single-phase samples of La_(1-x)Ca_xMnO_3 compounds have been synthesized by solid-state reaction. Detailed Rietveld analysis of powder X-ray diffraction data showed that La_(1-x)Ca_xMnO_3 undergoes a structural phase transformation from R-3c to Pnma at X = 0.05-0.075. There is a linear variation of lattice parameters as a function of calcium concentration. The slope of this linear variation changes at X = 0.6. A correlation between observed Mn-O bond lengths, corresponding to different compositions, and possible magnetic phases is discussed.