This research was undertaken to determine whether by powder diffraction substitution in the "123"-type high T_{c} oxides, Ln_{1-x}M_{x}Ba_{2-y}M_{y}Cu_{3-z}M_{z}O_{6.5+δ} (where Ln = lanthanoid, M_{x} = Me^{3+}, M_{y} = Me^{3+} and M_{z} = Me^{3+} and Me^{2+}) could be detected unequivocally. Numerous X-ray and a few neutron powder diffractograms were calculated for substituted compounds. Reflections most sensitive to substitution and the influence of site occupancy for Cu and O atoms are also characterized. The results are compared with some experimental data reported in the literature.
The lattice parameter for polycrystalline diamond is determined as a function of temperature in the 4-300 K temperature range. In the range studied, the lattice parameter, expressed in angstrom units, of the studied sample increases according to the equation a = 3.566810(12) + 6.37(41) × 10^{-14} T^{4} (approximately, from 3.5668 to 3.5673 Å). This increase is larger than that earlier reported for pure single crystals. The observed dependence and the resulting thermal expansion coefficient are discussed on the basis of literature data reported for diamond single crystals and polycrystals.
Two examples of transition metal molybdates were studied with the use of X-ray diffraction and DC magnetometry techniques. First compound, copper dimolybdate trihydrate CuMo_{2}O_{7}·3H_{2}O contains 2D layers. The second one is fibrillar cobalt trimolybdate octahydrate CoMo_{3}O_{10}·8H_{2}O. Both compounds exhibit paramagnetic behaviour at room temperature. However, in the first one copper ions form dimers linked by oxygen bridges, in which exchange interactions between two localized spin states occur. The second compound consists of isolated cobalt ions in the octahedral surroundings, resulting in magnetic properties deviating from the Curie law.
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