X-RAY-DIFFRACTION AND MOSSBAUER-EFFECT STUDIES ON SM1-XCAXFEO3-Y (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.70)

Samples of Sm1-xCaxFeO3-y are prepared in air for x ranging from 0 to 0.70. X-ray powder diffraction analysis shows that the samples are the single-phased perovskite-type compounds with the space group D2h16-Pbnm. The accurate lattice constants of Sm1-xCaxFeO3-y are calculated from the observed diffraction peaks by the least-squares refinement. Sm1-xCaxFeO3-y yields two hyperfine splitting patterns which would be assigned to iron(III) on octahedral sites and iron(III) on tetrahedral ones. The percentage of the iron on the tetrahedral sites increases almost linearly with increasing x, indicating that the oxygen vacancies in the lattice increase with the increasing substitution of Ca for Sm. The compounds prepared contain only trivalent iron, suggesting that they would have the chemical formula SM1-xCaxFeO3-x/2.