High Temperature X-ray Powder Diffractometry Research Articles

Effect of addition of LiAlSiO4 on microstructure, phase composition, and electrical properties of Li1.3Al0.3Ti1.7(PO4)3–based solid electrolyte

Li1.3Al0.3Ti1.7(PO4)3 (LATP) NASICON-type ceramic, due to its high bulk conductivity, is believed to be one of the most appropriate material for application as solid electrolyte in all-solid-state lithium-ion batteries. However, its highly resistant grain boundaries strongly limit the total ionic conductivity. Therefore, in this work, an attempt has been made to overcome this problem by introducing a Li-ion conducting additive LiAlSiO4 (LASO) to LATP base matrix in order to provide more conduction paths for lithium ions between grains. The properties of Li1.3Al0.3Ti1.7(PO4)3–xLiAlSiO4 (0.02 ≤ x ≤ 0.1) composite system were studied by means of: high-temperature X-ray powder diffractometry (HTXRD), 6Li, 27Al, and 31P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), scanning electron microscopy (SEM), and impedance spectroscopy (IS) methods. The obtained ceramic LATP–LASO materials exhibited high values of bulk conductivity, above 10−3 S/cm, and good total conductivity, exceeding 10−4 S/cm. The factors responsible for the enhancement, but also for the deterioration of total conductivity, i.e. microstructure and grain boundaries, are identified and discussed in this work.

On the synthesis and structure of the copper-molybdenum oxide bronzes: Monoclinic Cu2Mo10O30 and orthorhombic CuMo9O26

Cu2Mo10O30 was prepared as a monophasic material comprising dark blue platy crystals by reacting Cu with MoO3 under argon at 550 ​°C. Single-crystal X-ray diffractometry showed that Cu2Mo10O30 is a stoichiometric compound that crystallizes with a monoclinic (C2/c) cell: a ​= ​16.6359(6); b ​= ​9.3112(3); c ​= ​27.1597(9) Å; β ​= ​102.621(3)° (Z ​= ​8). Electron paramagnetic resonance spectroscopy revealed that Cu2Mo10O30 displays mixed-valency; (CuI2−xCuIIx)(MoV2+xMoVI8−x)O30 (0 ​≪ ​x ​≤ ​2). Differential scanning calorimetry and in situ high-temperature powder X-ray diffractometry showed that Cu2Mo10O30 decomposes ≳550 ​°C under an inert atmosphere. Dark blue acicular crystals of CuMo9O26 were discovered as a side-product in materials prepared inside evacuated glass ampoules at 500 ​°C. Single-crystal X-ray diffractometry showed these to crystallize with an orthorhombic (Pmmn) cell: a ​= ​3.74190(10); b ​= ​26.4941(4); c ​= ​9.15300(10) Å; (Z ​= ​2). Rietveld refinement of the powder X-ray diffraction data for these materials revealed Cu2Mo10O30 with minor CuMo9O26 and ‘Cu0.1MoO3’.

Investigation on thermophysical properties of RE6UO12(s) (RE = La, Pr, Nd, Sm)

RE6UO12(s) (RE=La, Pr, Nd, Sm) was synthesized by citrate-nitrate combustion method. The synthesis condition for Pr6UO12(s) was optimized. Nonstoichiometry in these rare earth uranates in argon atmosphere was analysed using various techniques like thermogravimetry (TG), X-ray photo electron spectroscopy (XPS), chemical analysis and electrical conductivity measurements. Thermal expansions of RE6UO12(s) (RE=Pr and Sm) was studied in the temperature range 298–1273K by high temperature X-ray powder diffractometry and compared with that of similar rare earth compounds reported in the literature. Heat capacity of RE6UO12(s) (RE=La, Pr, Nd, Sm) was measured by differential scanning calorimetry in the temperature range 300–870K. Enthalpy, entropy and Gibbs energy functions of these compounds were computed from the measured heat capacity data.

Combustion synthesis and thermal expansion of RE6UO12 (RE = Dy and Tb)

Citrate–nitrate combustion method was adopted for the synthesis of RE6UO12 (RE = Dy and Tb). These compounds were characterized by X-ray diffraction. Thermal expansion coefficient of these compounds were measured in the temperature range of 298–1,273 K by high temperature X-ray powder diffractometry (HT-XRD) and compared with other rare earth compounds reported in the literature. There was no observed phase transition in Dy6UO12, but Tb6UO12 showed a second-order phase transition at 670 K which was confirmed using differential scanning calorimeter. The average volume thermal expansion coefficient of Dy6UO12 in the temperature range of 298–1,273 K is (29.82 ± 4.02) × 10−6 and that of Tb6UO12 in the temperature range of 298–673 K is (13.76 ± 2.64) × 10−6 K−1.

Thermal expansion of lanthanum silicate oxyapatite (La9.33+2x(SiO4)6O2+3x), lanthanum oxyorthosilicate (La2SiO5) and lanthanum sorosilicate (La2Si2O7)

Four types of powder specimens of La9.33(SiO4)6O2 (space group P63/m and Z=1), La9.33+2x(SiO4)6O2+3x with 0.06≤x≤0.13 (P63/m and Z=1), La2SiO5 (P21/c and Z=4) and La2Si2O7 (P21/c and Z=4) were examined by high-temperature X-ray powder diffractometry to determine the changes in unit-cell dimensions up to 1473K. The anisotropy of thermal expansion was demonstrated for the former two crystals to clarify the thermal behaviors of the highly c-axis-oriented polycrystals. With La9.33(SiO4)6O2, the linear expansion coefficient of the a-axis (αa) was 4.8×10−6K−1 and that of the c-axis (αc) was 1.8×10−6K−1 in the temperature range from 298 to 1473K. The αa- and αc-values of La9.33+2x(SiO4)6O2+3x (0.06≤x≤0.13) were, respectively, 5.9×10−6K−1 and 2.3×10−6K−1. The coefficients of mean linear thermal expansion were 4.9×10−6K−1 for La2SiO5 and 6.0×10−6K−1 for La2Si2O7, which describe the thermal expansion behaviors of the randomly grain-oriented polycrystalline materials.

Heat capacity and thermal expansion coefficient of SrCeO3(s) and Sr2CeO4(s)

SrCeO3(s) and Sr2CeO4(s) were synthesized by citrate–nitrate gel combustion and solid state methods, respectively. Heat capacity of SrCeO3(s) and Sr2CeO4(s) were measured in high pure oxygen atmosphere by differential scanning calorimetry in the temperature range of 300–870K. Enthalpy, entropy and Gibbs energy functions were computed from the heat capacity data for SrCeO3 and Sr2CeO4(s) in the temperature range of 298–870K and 298–600K respectively. Thermal expansion measurements of these compounds were carried out in the temperature range of 298–1273K by high temperature X-ray powder diffractometry. The average value of coefficient of volume expansion for SrCeO3 and Sr2CeO4(s) were calculated in the temperature range of 298–1273K to be (10.79±2.31) and (23.22±5.19)×10−6K−1, respectively.

Geometric ferroelectricity in rare-earth compoundsRGaO3andRInO3

We have studied the stability and ferroelectric properties of hexagonal $R{\text{GaO}}_{3}$ and $R{\text{InO}}_{3}$ ($R$: rare-earth elements) by first-principles calculations. Computed spontaneous polarization in the series shows a systematic increase with the rare-earth elements, with values being larger in $R{\text{InO}}_{3}$ than in the corresponding $R{\text{GaO}}_{3}$. The largest polarization found is about $10\text{ }\ensuremath{\mu}\text{C}/{\text{cm}}^{2}$ for ${\text{ErInO}}_{3}$, which is about twice as large as those observed in hexagonal $R{\text{MnO}}_{3}$. The polarization can be further increased by applying in-plane compressive stress. The Born effective charges of constituent ions in the compounds are found to be similar to their formal values, implying that the ferroelectric displacements are merely driven by the ionic size effect. A transition to the high-symmetry phase at around 1500 K was confirmed in ${\text{GdInO}}_{3}$ and ${\text{DyInO}}_{3}$ by in situ high-temperature powder x-ray diffractometry. The present systems should belong to the family of geometric ferroelectrics.

Thermal expansion and heat capacity of Gd 6UO 12(s)

Gd 6UO 12(s) was synthesized by citrate–nitrate combustion method. Thermal expansion measurements of this compound were carried out in the temperature range of 298–1273 K by high temperature X-ray powder diffractometry and compared with other rare earth compounds of similar stoichiometry reported in literature. Heat capacity of Gd 6UO 12(s) was also measured by differential scanning calorimetry in the temperature range of 330–720 K. Enthalpy, entropy and free energy functions for Gd 6UO 12(s) were computed.

Thermal dehydration of lithium metaborate dihydrate and phase transitions of anhydrous product

Reaction steps and mechanisms of the thermal dehydration of lithium metaborate dihydrate were investigated by means of thermoanalytical measurements, high temperature powder X-ray diffractometry, FT-IR spectroscopy, and microscopic observations. The first half of thermal dehydration was characterized by the melting of the sample producing viscous surface layer, the formation of bubbles on the particle surfaces, and the sudden mass-loss taking place by an opportunity of cracking and/or bursting of the bubble surface layer. The second half of the dehydration with a long-tailed mass-loss process in a wide temperature region was divided further into three distinguished reaction steps by the measurements of controlled rate thermal analysis. During the course of the thermal dehydration, four different poorly crystalline phases of intermediate hydrates were observed, in addition to an amorphous phase produced by an isothermal annealing. Just after completing the thermal dehydration, an exothermic DTA peak of the crystallization of β-LiBO 2 was appeared at around 750 K. The phase transition from β-LiBO 2 to α-LiBO 2 was observed in the temperature range of 800–900 K, which subsequently melted by indicating a sharp endothermic DTA peak with the onset temperature at 1101.4 ± 0.6 K.

Phase transition of BaNd 2Mn 2O 7

Phase transition of BaNd 2Mn 2O 7 from orthorhombic (space group Fmmm) to tetragonal phase ( I4/ mmm) was studied by high temperature powder X-ray diffractometry and Rietveld analysis. The transition temperature was identified at 523 K, which is almost the same transition temperature as the compounds with other rare earth ions in this BaLn 2Mn 2O 7 family (Ln = Sm and Eu) with Fmmm space group. During the transition an oxygen octahedron of each phase changes a little its form, in which four oxygen atoms perpendicular to c-axis make a rectangle and a square for orthorhombic and tetragonal phases, respectively. Manganese ion is not on the center of the quadrilateral consisting of these four oxygen ions, but a little apart from the center along c-axis in both phases.

Crystal structure and dielectric properties of complex perovskite (Sr, Ba, Ca)(Ni 0.5W 0.5)O 3

A-site cation substitution with Ba 2+ and Ca 2+ was made for the complex perovskite Sr(Ni 0.5W 0.5)O 3 to correlate with the structure evolution and the temperature coefficient of dielectric constant. The crystal structures of the solid solutions at elevated temperatures were studied using high temperature X-ray powder diffractometry. A single phase of the perovskite was obtained and ordering of the cations in B-site was observed for all compositions of the solid solutions sintered at 1400 °C for 24 h. The crystal symmetry of the solid solutions at room temperature was changed from monoclinic→rhombohedral→orthorhombic→cubic with the corresponding A-site cation species of Ca 2+→Sr 2+→Ba 2+. The orthorhombic phase of Sr(Ni 0.5W 0.5)O 3 was transformed to the cubic phase at 300 °C. The phase transformation from rhombohedral to cubic at elevated temperatures was observed for each of the Ca 2+-substituted solid solutions, and the phase transformation temperatures increased with increasing Ca 2+ content. Another phase transformation from monoclinic to rhombohedral gradually occurred for (Sr 0.2Ca 0.8)(Ni 0.5W 0.5)O 3 between 400 and 600 °C. Phase transformation was not observed for Ca(Ni 0.5W 0.5)O 3 in the temperature range from room temperature to 1200 °C. Dielectric constants of the solid solutions at room temperature were approximately 27–33. Temperature dependence of dielectric constant was measured in the temperature range from −100 to 500 °C and the temperature coefficients of dielectric constant for each of the solid solutions are discussed correlating with the changes in the crystal symmetry during heating.

Crystallographic phase transition, electrical and magnetic properties of stoichiometric La(Mn,Rh)O 3

Temperature-induced phase transitions, electrical conductivity, and some magnetic properties of stoichiometric LaMn 1− x Rh x O 3 (0.1≤ x≤0.5) have been studied. The phase transitions of LaMn 0.9Rh 0.1O 3 were investigated by high-temperature X-ray powder diffractometry and orthorhombic–pseudocubic–rhombohedral transitions were observed. The electrical conductivity measurement shows semiconducting property above room temperature. Breaking of slope in the temperature dependence of the conductivity bring the evidence in support of the phase transition for LaMn 0.9Rh 0.1O 3. At low temperature, the compounds show ferromagnetic behavior but the ferromagnetic intensity increases with the increase of the oxygen nonstoichiometry.

Low‐Thermal‐Expansion Properties of Sodium‐ and Lithium‐Substituted Cubic Cesium Leucite Compounds

Cubic cesium leucite‐based compounds, namely cesium leucites, cesium sodium leucites, and cesium lithium leucites, were synthesized using a multistep solid‐state reaction method. The thermal expansion properties, in the temperature range of 298‐1273 K, for the synthesized cubic cesium leucite‐based compounds were examined using high‐temperature powder X‐ray diffractometry data. The thermal expansions of the cubic cesium leucite‐based compounds were found to vary with the chemical composition. For instance, the thermal expansions of Cs0.7Na0.2Al0.9Si2.1O6 and Cs0.7Li0.2Al0.9Si2.1O6 were 0.14% at 1273 K and 0.081% at 1073 K, values lower than those of Cs0.9Al0.9Si2.1O6, which were 0.16% at 1073 K and 0.2% at 1273 K. The results showed that the thermal expansions of the cubic cesium leucite‐based compounds changed with ionic substitution at the Cs+ sites because of ionic size differences between Cs+ and the Na+ or Li+ substitutional ions.

Anisotropic thermal expansion in yttrium silicate

In this study, crystals of Y2SiO5 were examined by high-temperature powder x-ray diffractometry to determine the changes in unit-cell dimensions with temperatures up to 1273 K for the X1 phase (the low-temperature phase, space group P121/c1) and 1473 K for the X2 phase (the high-temperature phase, space group I12/a1). The lattice deformations of both phases induced by thermal expansion were investigated by matrix algebra analysis to determine the directions and magnitudes of the principal distortions (λi, i = 1, 2, and 3). For the X1 phase, λ1 and λ2 invariably showed a positive thermal expansion. On the other hand, λ3 showed a negative thermal expansion below 1173 K; the maximum contraction of 0.10(4)% occurred at 685 K. The λ2 axis invariably coincides with the crystallographic b axis. The directions of λ1 and λ3, defined by the acute angle λ3 ^ c changed between 53(3)° (T = 394 K) and 45(1)° (T = 788 K). For the X2 phase, all of the principal distortions steadily increased with increasing temperature. The angle λ3 ^ c steadily decreased from 71(2)° to 62.1(1)° with increasing temperature. The mean linear thermal expansion coefficients were, when compared at the same temperatures, necessarily higher for the X1 phase than for the X2 phase. The lattice change of X1–RE2SiO5 (RE = Y and Yb–La), which was induced by the substitution of rare-earth (RE) ions, showed a striking resemblance with the lattice deformation of X1-Y2SiO5, which was caused by the thermal expansion. Because the lattice change of the former must be caused by the isotropic expansion of the RE sites, the anisotropic thermal expansion of the latter would be essentially attributable to the isotropic thermal expansion of the YO9 and YO7 polyhedron.

Anisotropic Thermal Expansion in CaAl4O7

Crystals of CaAl4O7 (space group C2/c) have been examined by high-temperature powder x-ray diffractometry to determine the change in unit-cell dimensions with temperature up to 1473 K. The lattice deformation induced by thermal expansion has been investigated by matrix algebra analysis to determine the directions and magnitudes of the principal distortions. During heating from 298 K, two of the three principal distortions, λ1 and λ2, invariably showed a positive thermal expansion, the magnitudes of which at 1473 K are respectively approximately 1.0% and approximately 0.8%. The direction of λ1 was nearly parallel to [304], and the λ2 axis invariably coincides with the crystallographic b axis. On the other hand, the distortion λ3 showed a negative thermal expansion below approximately 1173 K; the maximum contraction of approximately 0.2% occurred at approximately 673 K nearly along [207]. During further heating to 1473 K, λ3 showed, to the contrary, a positive expansion of approximately 0.2% nearly along [50, 16]. The negative thermal expansion along the λ3 axis substantially accounts for the mean linear thermal expansion being very low at temperatures below approximately 473 K.

HT-XRD, IR and Raman characterization studies of metastable phases emerging in the thermal genesis course of monoclinic zirconia via amorphous zirconium hydroxide: impacts of sulfate and phosphate additives

High-temperature X-ray powder diffractometry was performed on pure and impregnated (with sulfate and phosphate additives) Zr(OH) 4 while being in situ heated (in air) to different temperatures up to 1000 °C. Accordingly, portions of these materials were ex situ calcined at some selected temperatures within the temperature regime examined. The calcination products were subjected to Fourier-transform laser Raman and infrared spectroscopic analyses. The results showed the pure hydroxide to decompose into low-temperature stable monoclinic zirconia ( m-ZrO 2) in a slow process intermediated by metastable tetragonal ( t-ZrO 2) and/or cubic ( c-ZrO 2) phases. The metastability of the intermediate phases was, therefore, considered to be a consequence of the slow kinetics of conversion. Moreover, high surface energy (small particle size) of these phases was suggested as an additional reason for their existence, in terms of consistent literature data. The sulfate and, particularly, phosphate additives were shown to slow further the formation of m-ZrO 2. This has been suggested to arise from (i) suppression of particle sintering (growth), and (ii) phosphate stabilization (most likely) of c-ZrO 2. Results of the present investigation may help a better understanding of phase transitions occurring during the thermal genesis of zirconia-based solid acids from an amorphous parent material, a domain that has hitherto received little agreement in the literature.

Dilatometric and high temperature X-ray diffractometric studies of La 1− xM xCrO 3 (M=Sr 2+, Nd 3+, x=0.0, 0.05, 0.10, 0.20 and 0.25) compounds

The phase transition, bulk and lattice thermal expansion behaviour of the strontium and neodymium substituted lanthanum chromites have been studied by dilatometry and high temperature X-ray powder diffractometry from room temperature to 1123 and 1073 K, respectively, in static air. The studies revealed that the temperature of the orthorhombic to rhombohedral phase transition, which occurred at ∼550 K in undoped LaCrO 3, decreased on substitution of Sr 2+ ions and increased on substitution of Nd 3+ ions, systematically. However, the coefficients of average linear and volume thermal expansion ( α l and α v) of LaCrO 3 showed a marginal increase on Sr 2+ substitution to different extent, whereas a reverse trend was observed with Nd 3+ substitution. The phase transition temperatures and α l and α v of the compounds as determined by dilatometric and high temperature X-ray diffractometric methods are reported.

Combustion synthesis and thermal expansion measurements of the rare earth–uranium ternary oxides RE 6UO 12 (RE=La, Nd and Sm)

Rare earth–uranium ternary oxides were synthesized by a solution combustion route. The starting materials were the corresponding metal nitrates and urea. In these preparations, the metal nitrates act as oxidizer and urea as fuel. Highly exothermic decomposition of the metal nitrate–urea complexes on heating at about 500 K leads to a combustion process yielding RE 6UO 12 fine powders. Thermal expansion measurements of these compounds were carried out in the temperature range of 298–1173 K by high temperature X-ray powder diffractometry. The observed axial thermal expansion behaviour is explained on the basis of the crystal chemistry of the compounds.

Thermoelasticity of belite in Portland cement clinker

Belite crystals, separated from an industrial cement clinker, were examined by high-temperature powder X-ray diffractometry. We determined the starting and finishing temperatures of the α′ L-to-β martensitic transformation and those of the reverse (β-to-α′ L) transformation. The thermal hysteresis was negative (−65°C), indicating the thermoelasticity of the transformation. Each of the transformation temperatures was lower than that of pure Ca 2SiO 4. Because the finishing temperature of the α′ L-to-β transformation was higher than ambient temperature, the α′ L-phase was entirely inverted to the β-phase during cooling.

Thermal expansion studies on the Sodium Zirconium Phosphate family of compounds A1/2M2 (PO4)3: effect of interstitial and framework cations

Thermal expansion of the sodium zirconium phosphate (NZP) family of compounds A1/2M2(PO4)3 (A = Ca or Sr; M = Ti, Zr, Hf or Sn) has been measured in the temperature range 298–1273 K by high-temperature X-ray powder diffractometry. Some of the compounds in the series (calcium zirconium phosphate and calcium hafnium phosphate) display the typical thermal expansion behaviour of NZP compounds, namely expansion along the hexagonal c axis and contraction along the a axis. The other compounds, depending on their interstitial and framework composition, behave differently. The observed axial thermal expansion and contraction behaviour is explained on the basis of the crystal chemistry of the compounds. Low-expansion compounds in this series are identified and their expansion anisotropy examined. Infared spectra of the compounds are reported. Differential scanning calorimetry measurements on the tin compounds indicate the occurrence of a diffuse phase transformation at high temperatures.