X-ray diffraction analysis of stannite, wurtz-stannite and pseudo-cubic quaternary compounds by Rietveld method
Room temperature X-ray powder diffraction measurements were carried out on nine polycrystalline samples of the Cu2B II C IV X4 (B=Mn, or Fe, or Co; C=Si, or Ge, or Sn; X=S, or Se, or Te) magnetic semiconductor compounds. The diffraction patterns were used to show the equilibrium conditions and to derive crystalline parameter values. The results showed that four of these compounds have a tetragonal stannite structure with space group 142m(N° 121), two an orthorhombic wurtz-stannite structure with space group Pmn2(1)(N° 31) and three of them an orthorhombic pseudo-cubic structure with space group F222 (N° 22). In each case, the structure was refined using the Rietveld method. When the obtained atomic parameter values for the tetragonal compounds were plotted as a function of molecular weight W, it was found that the values of the atomic positions, the cation-anion bond distances, tetragonal distortion and internal distortion of the compounds containing S and/or Se lay on different lines. Also, it was found that when the experimental points of the cation-anion bond distances dCu-VI, dII-VI and dIV-VI were plotted against the effective lattice parameter a e = (V/N)1/3, a linear variation of these distances with a e was obtained. Values of the ionic energy gap Ci and homopolar energy gap Eh using the Phillips-Van Vechten scheme, with the present experimental crystallographic results as well as using the atomic data, were determined. It was found that the observed and predicted values of Ci and Eh lie on the same straight line.
| Main Authors: | , , , , , , , , , , |
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| Format: | Digital revista |
| Language: | English |
| Published: |
Sociedad Mexicana de Física
2014
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| Online Access: | http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2014000200013 |
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