Hanèn Chaker

Rietveld refinement of X-ray powder data and bond-valence calculations of NdSrNi0.5Cr0.5O4-δ compound

Compound from the solid-solution NdSrNi 1− x Cr x O 4−δ , 0≤ x ≤1, has been prepared using conventional solid-state method and was characterized by X-ray powder diffraction. The NdSrNi 0.5 Cr 0.5 O 4−δ sample shows the adoption of the K 2 NiF 4 -type structure based on the tolerance factor calculation. X-ray diffraction analysis using the Rietveld method was carried out and it was found that NdSrNi 0.5 Cr 0.5 O 4−δ compound crystallizes in tetragonal symmetry with space group I 4/ mmm . The lattice parameters are found to be at room temperature, a =3.8012(3) A and c =12.4812(1) A. For X-ray diffraction data, the reliability factors are R B =0.034, R wp =0.089, , and χ 2 =1.17. Bond-valence sum calculations were performed for nickel and chromium. The changes in unit-cell parameters are discussed in terms of oxygen stoichiometry and transition metal (3 d ) oxidation state from the perspective of the Brown bond-valence sum calculation theory.

Rietveld refinement of the gadolinium strontium oxide SrGd 2 O 4

Powder X-ray diffraction (XRD) data were collected for a new phase of SrGd 2 O 4 . Analysis using the Rietveld method was carried out and it was found that the sample crystallizes in the orthorhombic symmetry with CaFe 2 O 4 related structure. The lattice parameters are found to be a =12.0521(2) A, b =10.1327(2) A, c =3.4757(4) A and Z =4. For X-ray data R F =4.9%, R B =7.6%, R P =8.1% and χ 2 =1.51. The structure can be described as an assembly of bioctahedron [Gd 2 O 10 ] which are linked together by O 2− anions and of dodecahedron of SrO 8 .