[en] The samples of Y₃Fe_(5-x)Al_xO₁₂ (x=1, 2, 3, 4, 5) were sintered from corresponding mixed hydroxides that were obtained by coprecipitation of mixed nitrates. The neutron diffraction experiments were done, for all the samples, at 295 and 10 K. All the samples crystallize in the garnet structure type. The iron and aluminum ions occupy tetrahedral and octahedral positions. The preferential distribution of these cations is found. The iron ions preferentially occupy octahedral positions, the smaller aluminum ions preferentially occupy the smaller tetrahedral positions. The samples with x=1, 2 are collinear ferrimagnetics, with antiparallel moments in tetrahedral and octahedral positions, at 10 K. The sample with x=1 retains this magnetic order at 295 K. The magnetically ordered phases were refined in the cubic space group Ia3d and in the rhombohedral space group R-3c. In the rhombohedral space group the magnetic moments of the iron ions at 10 K are -3.94(6) and -3.6(1) μ_B in the tetrahedral position and 4.28(5) and 3.75(7) μ_B in the octahedral position, for samples with x=1, 2, respectively. In the R-3c the total magnetic moment, per formula unit, agrees with the results of the classical magnetic measurements. Both samples (x=1, 2) are rhombohedral at low temperatures and the symmetry of x=1 sample approaches the cubic with the increase of temperature

[en] The X-ray powder diffraction patterns of La_2-xEr_xO₃ (x=0.2, 0.3, 1, 1.8, 2) samples were refined by the Rietveld full profile method. The magnetic susceptibility was measured in the temperature range 4-300 K, and the magnetic behavior of trivalent erbium ion is discussed in connection with the different local symmetry sites

[en] The polycrystalline samples of Tm_xY_2-xO₃ (x=0.1, 0.2, 0.4, 0.6, 1, 1.4, 1.8) were obtained by ceramic technology. X-ray diffraction data were collected and the crystal structures were refined by the Rietveld method. A random distribution of Tm³⁺ ions over two cationic sites, 8b and 24d, in the space group Ia3-bar was found. Magnetic susceptibility measurements of all samples were done using a SQUID susceptometer in a temperature range 4 K< T<290 K. Above 90 K a Curie-Weiss law was observed, while below 90 K the inverse magnetic susceptibility deviates from linearity due to the crystal-field influence. Deduced effective magnetic moments are close to the free ion values. In the whole temperature range the susceptibility data were fitted in accordance with the axial symmetry approximation of the crystal field and corresponding values of the crystal-field energy levels were deduced

[en] Powder mixture of Ca(OH)₂-P₂O₅-CaF₂ were milled in planetary ball mill. A carbonated fluorhydroxyapatite, FHA Ca₁₀(PO₄)_1-y(CO₃)_y(PO₄)₅(OH)_2-2x1(F)_2x1 was formed after 5 h of milling and carbonated fluoroapatite Ca₁₀(PO₄)_1-y(CO₃)_y(PO₄)₅(F)₂ was formed after 9 h of milling. Complete transformation of the carbonated form of FA into then single phase of FA occurred after 9 h milling and thermally treating. The various experimental techniques like X-ray Diffraction (XRD), Differential Thermal Analysis (DTA), Infrared Spectroscopy (IR), Transmission Electron Microscopy and Scanning Electron Microscopy (SEM) were used to characterize the synthesized powders and to postulate reaction mechanisms' steps- transformations of reactants involved

[en] Polycrystalline samples of cadmium-manganese mixed oxides Cd_1-xMn_xO were synthesized by ceramic technology in a wide range of concentrations x (0.05≤ x≤0.90). Their crystalline structures were investigated by the Rietveld profile method based on the x-ray powder diffraction measurements. All samples were found to be of sodium chloride structure type with lattice constants a(x) slightly deviating from the Vegard law. Thermogravimetric analysis shows that samples are unstable above 500 K owing to the absorption of oxygen by MnO. Magnetic susceptibility χ(x, T) measurements made by the Faraday method indicated the presence of antiferromagnetic interactions between Mn²⁺ ions. In the paramagnetic region the Curie-Weiss law is obeyed with the linear dependence on the concentration of the effective paramagnetic temperature Θ(x) and Curie molar constant C_M(x). From the analysis of the magnetic susceptibility data, values of the spin and the nearest-neighbour exchange integral were found to be S=2.6±0.1 and J₁/k_B=11±1 K, respectively. (author)

[en] Mixed sesquioxides Y_2-xEu_xO₃ (x = 0.10, 0.20, 0.60, 1.00, 1.60 and 1.80) in the cubic (C) phase were obtained by precipitation and subsequent sintering. Cubic Eu₂O₃ and Y_0.20Eu_1.80O₃ were transformed into monoclinic (B) phases at 1400 K and 1600 K respectively. The transformation is reconstructive in character. All of the structures were refined using the Rietveld powder method, and the Eu³⁺ ions found to be randomly distributed. The molar magnetic susceptibilities at room temperature exceed the free-ion values, and are almost independent of the concentration for x≥0.60. For x≤0.20, the susceptibilities decrease with decreasing concentration of the magnetic ion Eu³⁺. This behaviour is attributed to crystal-field and anisotropic exchange effects. (author)

[en] The polycrystalline samples of Y_2-xHo_xO₃ (0.10≤x≤1.80) were synthesized by ceramic technology. The X-ray powder diffraction data were collected and the crystal structures were refined by the Rietveld method for the samples Y_2-xHo_xO₃ (x=0.00, 0.20, 0.40, 1.20, 1.80, 2.00). Holmium ions Ho³⁺ were randomly distributed over two cationic sites 8b and 24d in the space group Ia3 in all refined structures. Cation-anion-cation bonds important for superexchange interaction were determined. Magnetic susceptibility measurements were done by the Faraday method in the temperature range 290 to 620 K and a behaviour in accordance with the Curie-Weiss law was obtained. The molar Curie's constants linearly depend on concentration. The effective magnetic moments of Ho³⁺ ions were smaller than the free ion value. The Curie-Weiss paramagnetic temperatures indicated antiferromagnetic interaction. The gram ion susceptibilities confirmed the random distribution of Ho³⁺ ions over two crystallographic sites in the concentration range 0.20≤x≤2.00 and pointed to the random distribution of magnetic ions in the sample with x=0.10. The nonlinearity of Curie-Weiss paramagnetic temperatures versus concentration occurred in the low concentration region (x≤0.40), indicating tendency of magnetic ions to form small clusters around cationic sites. ((orig.))

[en] Lithium-indium oxide is one of the candidate materials as solid-state scintillators for solar neutrinos due to an inverse β^--decay of ¹¹⁵In to ¹¹⁵Sn. On the other hand, when doped with rare-earth ions such as Eu³⁺ or Sm³⁺, it becomes a promising phosphor material. In this report we present a simple solid-state procedure for preparation of LiInO₂:Eu³⁺ powders. X-ray diffraction confirmed prod-uct in tetragonal structural form (space group: I4₁/amd) and no impurity phases were detected. Then, high resolution photoluminescence emission measurements were performed at room and low temperatures to find ⁵D₀ → ⁷F_J. Emission kinetics from ⁵D₀ level exhibited pure single exponential behavior with lifetime of about 1.5 ms. Maximum energy splitting of ⁷F₁ manifold is recorded as a function of temperature (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Polycrystalline samples of the new semimagnetic semiconductor Yb_xY_2-xO₃ (x=0.06, 0.12, 0.25, 0.39, 1.00, 1.40, 1.80) were obtained by ceramic technology. An x-ray diffraction experiment was performed on all of the samples at room temperature. These data provided the basis for Rietveld refinements. The refinements showed that Yb³⁺ ions preferentially occupy the 24d position. The lattice constants and the mean cation - anion distances decrease linearly with the Yb³⁺-ion concentration. The inverse magnetic susceptibilities for all of the samples depend linearly on the temperature for 4K< T<30 K. In this region only the lowest Kramer's doublet is populated, and for that level the effective magnetic quantum number M_1eff is deduced. The Curie-Weiss paramagnetic temperatures θ(x) obtained from the low-temperature region depend linearly on the concentration x. Over the whole experimental region 4K< T<250 K, the magnetic susceptibility deviates from the Curie-Weiss law, and its calculation requires inclusion of the first excited Kramer's doublet. The effective magnetic quantum number M_2eff and energy gap ΔW of the first excited doublet were deduced. (author)

[en] In order to determine the rare earth ion distribution in Re_xY_2-xO₃ (Re=Gd, Dy, Ho, Er), for 0< x<2, the X-ray diffraction and the magnetic measurements were done. The preferential and the random distributions of the magnetic ions over two crystallographic sites, depending on Re³⁺ ion nature, and their clusterization were found. ((orig.))