Papers by Keyword: X-Ray Powder Diffraction

Abstract: Rare earth-transition metal (R-T) intermetallics have been well used because of their excellent properties. The X-ray diffraction patterns of many new phases in the R-T system have not been extensively studied. A new compound AlCrNi₃Pr was prepared by arc melting using non-consumable tungsten electrode under argon atmosphere, and then annealed at 1023K for 30 days. The X-ray powder diffraction data of AlCrNi₃Pr was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed, and the structure refinement by using Rietveld method indicated that the AlCrNi₃Pr compound crystallized in the hexagonal structure, space group P6/mmm (No.191) with PrNi₅ structure type, a=b=5.0553(9) Ǻ, c=4.0763(6) Ǻ, V=90.22Ǻ³, Z=1, ρ_x=7.288g cm^-3, the Smith–Snyder FOM F₃₀=279.1(0.0044, 32) and the intensity ratio RIR=1.23.

Abstract: The quantitative phase analyses of a slag have been successfully carried out by using both of the full-profile Rietveld and RIR methods from X-ray powder diffraction data. The qualitative phase analysis indicates that the slag contains mayenite (CaO)₁₂(Al₂O₃)₇, olivine Ca₂(SiO₄), gehlenite Ca₂Al (AlSiO₇), lemite Ca₂(SiO₄) and hibonite CaO(Al₂O₃)₆. The quantitative analysis from Rietveld refinement shows that the weight concentrations of mayenite, olivine, gehlenite, lemite and hibonite for the slag are 48.8(4) wt.%, 32.2(5) wt.%, 11.0(9) wt.%, 6.2(1.1) wt.% and 1.8 (1.2) wt.%, respectively. The quantitative phase analysis results obtained by Rietveld method are more precise then those by RIR method.

Abstract: The NiTi shape memory alloys with ternary additions of Co are being considered for future applications in the construction of medical products. In this study the commercially available Ni_50.8Ti_49.2 medical alloy and Ti₅₀Ni_48.7Co_1.3 alloy obtained by the conventional VIM technique, were used to prepare shape memory and superelastic staples. The phase transformations in the wires of those alloys after various thermo-mechanical and thermal treatments have been defined by the differential scanning calorimetry (DSC) method and three-point bending and free recovery ASTM F2082-06 tests. In this work the courses of phase transformations in the studied alloys were investigated by means of the low-temperature X-ray powder diffraction method. In both alloys after cold working and annealing during cooling two phase transformations occur: from parent B2-phase to rhombohedral R-phase and monoclinic B19’ martensite phase. Such phase transformations are fully reversible during heating and the obtained characteristic temperatures from DSC and X-ray powder diffraction measurements are in good agreement.

Abstract: Nasicon type compounds of general formula Li1..3M0.3Ti1.7 (PO4)3 (M = Al, Cr, Fe) were prepared using melt quenching method. The samples were characterized by X-ray powder diffraction and infrared spectra. Thermal stability against crystallization was evaluated by DSC curve. All the compounds crystallize in hexagonal lattice with R-3c space group. The IR spectra show the characteristic PO4 vibrations. DSC curve reveals that the Li1.3Fe0.3Ti1.7(PO4)3 glass-ceramics possesses the better thermal stability against crystallization. Conductivity studies indicate that the total conductivity is dominated by the grain boundary

Abstract: The structure of the new ternary compound Hf₂GaSb₃ was determined by means of X-ray powder diffraction. It crystallizes with the structure type Zr₂CuSb₃ which represents a ternary ordered derivative of the UAs₂ type (Pearson symbol tP6, space group P-4m2, a = 3.89841(8), c = 8.62650(19) Å). The ternary compound can be regarded as an ordered, Ga-stabilized derivative of the high-temperature modification of the binary antimonide HfSb₂ (structure type UAs₂).

Abstract: The addition of silicon ions to hydroxyapatite (HA) provides a more inorganic bone-like chemical composition compared to stoichiometric HA. It is known to aid the bioactivity of the material and to improve the rates of osseointegration, osteoconduction and bone mineralisation. The literature, however, lacks detailed information regarding each step of the aqueous precipitation procedure to produce silicon-substituted HA (Si-HA). The current work utilised Raman spectroscopy at each stage of the aqueous precipitation method to determine how the silicate is incorporated into the HA structure when producing Si-HA. Raman spectra indicated that at the initial stages of the reaction the disilicate ion (Si₂O₇^6-) formed with the orthosilicate (SiO₄^4-) ion becoming more dominant after sintering. The results demonstrated that the form of silicate in the Si-HA aqueous precipitation method can be tracked using Raman spectroscopy.

Abstract: This study successfully synthesized manganese-doped calcium zirconate phosphor and manganese-doped strontium zirconate phosphor using the sol-gel method. We employed X-ray powder diffraction and fluorescence spectroscopy to analyze the crystal structure and spectral characteristics of both phosphors. In X-ray powder diffraction analysis, data related to manganese-doped calcium zirconate phosphor and manganese-doped strontium zirconate phosphor were compared using X-ray diffraction comparison software to confirm the crystal structures of both phosphors. The crystal structure of manganese-doped calcium zirconate phosphor was in accordance with orthorhombic perovskites belonging to the Pnma {62} space group. The lattice parameters were a=5.762 Å, b=8.017 Å, and c=5.591 Å; c/a=0.97; volume=258.3 ų, and density=4.611 g/cm³. The crystal structure of manganese-doped strontium zirconate phosphor conformed to orthorhombic perovskites belonging to the Pnma {62} space group, and the lattice parameters were a=5.818 Å, b=8.204 Å, c=5.797 Å; c/a=0.996; volume=276.7 ų, and density=5.446 g/cm³. Fluorescence spectroscopy indicated that the primary broadband peak of manganese-doped calcium zirconate phosphor was located at 396.6 nm in the excitation spectrum corresponding to the ⁴T₂(⁴G)⁴T₁(⁴P) energy level transition. In the emission spectrum, the primary broadband peak was located at 596.6 nm, corresponding to the ⁴T₂(⁴D)⁴T₂(⁴G) energy level transition. For manganese-doped strontium zirconate phosphor, the primary broadband peak was located at 496.6 nm in the excitation spectrum and at 696.6 nm in the emission spectrum, corresponding to the ⁴T₁(⁴G)⁴T₂(⁴D) and ⁴E(⁴G)⁴T₁(⁴G) energy level transitions, respectively.

Abstract: YAG is widely applied as the structure materials and the functional materials because of some excellent performances in the chemistry. The pure superfine YAG powder materials are prepared via the co-precipitation method after calcining the precursor of YAG at 1100°C. The superfine YAG powders has the better dispersion, the particle size distribution range is narrow bewteen 200 and 350nm. The superfine YAG mainly show near-spherical, and partly sintering behavior among the particles.

Abstract: The phase equilibria in Al-rich corner of the Al-Zn-Ti ternary system at 400 °C were determined by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and X-ray powder diffraction (XRD). The results showed that this section consisted of three ternary-phase regions, namely, L+(Al)+τ, Ti₂Al₅+τ+(Al) and Ti₂Al₅+TiAl₃+(Al). The XRD patterns and EDS confirmed that a Ti₂Al₅-structured phase with containing 4 at.% Zn was stable at 400 °C. Furthermore, the ternary new phase (τ phase) was identified in samples and in equilibrium with (Al), Ti₂Al₅ and liquid, respectively.

Abstract: Using cadmium acetate and sodium sulfuret as Cd and S sources, CdS samples were synthesized by chemical precipitation method. The conditions of supersaturation and aging time had been investigated, which could influence the activity of CdS for photocatalytic degrading methyl orange. The products were characterized by X-ray powder diffraction and field emission scanning electron microscopy. The CdS samples synthesized under low supersaturation showed better photocatalytic activities. A phase transformation of hexagonal CdS to cubic CdS was observed when CdS precipitation aging and the presence of proper amount of hexagonal CdS should improve the photocatalytic performance of cubic CdS.