Type Solid Solution Research Articles

TiO2-ZrO2系の高圧相関係とα-PbO2型固溶体の形成

TiO2-ZrO2系の高圧相関係とα-PbO2型固溶体の形成

Measurement and Properties of the Oxide Ionic Conductivity of β- and δ-Phases in the Binary (Bi2O3)1−x (Tb4O7) x System

The total conductivity (σT) in the β-phase and δ-Bi2O3 doped with Tb4O7 system was measured in the composition range between 1 and 30 mol% Tb4O7 at different temperatures. According to the DTA/TG results, this tetragonal type solid solution was stable up to about ∼740°C, and the solubility limit was found at ∼5 mol% Tb4O7 in the β-phase; this fcc type solid solution was stable up to about ∼740°C, and the solubility limit was found at ∼30 mol% Tb4O7 in the δ-phase. All phases showed predominant oxide ionic conduction. It has been proposed that β- and δ-Bi2O3 phases contain a large number of oxide anion vacancies and incorporated terbium cations at tetrahedral sites that affect the oxygen sublattice of the crystal structure.

Oxidation behaviors of Nb-15W and Nb-15W-10Cr alloys fabricated by vacuum hot-pressing sintering

Vacuum hot-pressing sintering (VHPS) was used for fabricating Nb-15W and Nb-15W-10Cr (at.%) alloys under 30 MPa for 60 min at 1800 °C in pure argon atmosphere. Microstructure and oxidation resistance of both materials were investigated. Microstructure analysis showed that the as-sintered Nb-15W alloy only consisted of α-Nb (W) solid solution and the as-sintered Nb-15W-10Cr alloy composed of α-Nb (W, Cr) solid solution and small amount cubic type NbCr2 Laves phase due to addition of 10 at.% Cr. The oxidation at 1300 °C for 4 h exhibited that the addition of 10 at.% Cr increased the oxidation rate of Nb-15W alloy. The effects of Cr on the oxidation behaviors are discussed in detail.

The conversion of phase diagrams of solid solution type into electrochemical synthesis diagrams for binary metallic systems on inert cathodes

A method has been developed to convert equilibrium phase diagrams into equilibrium electrochemical synthesis diagrams (EESDs) using the same Calphad (Calculation of the Phase Diagrams) type of information behind them. The method is developed for binary ( A–B) metallic systems electrodeposited from an electrolyte containing cations A + n and B + m on inert cathodes in a galvanostatic regime at very low cathodic current densities, i.e. close to equilibrium. The EESD shows the equilibrium composition of different phases in the equilibrium cathodic product at fixed values of temperature and pressure as a function of parameter Δ E B , being the deposition potential of one of the components ( B) relative to another ( A). The key to construct the EESD is a new equation derived for the synthesis potential of the alloy as a function of Δ E B , the charges the ions n and m in the electrolyte and the Gibbs energy of the cathodic product (alloy) as a function of its composition, temperature and pressure. The general method of phase diagram construction (i.e. the Gibbs energy minimization) is converted during the construction of the EESDs into the method of synthesis potential maximization. The given EESD is generally valid for the corresponding binary metallic A–B system, independent of the electrolyte (for the given values of n and m). The EESD can be used to design electrochemical synthesis of alloys if parameter Δ E B is known as a function of the composition of the given type of electrolyte (ionic liquid, aqueous solution, molten salt, etc.) at given temperature and pressure. In the present paper the method is developed to construct EESDs for phase diagrams of solid solution type.

Phase Evolution, Phase Transition, Raman Spectra, Infrared Spectra, and Microwave Dielectric Properties of Low Temperature Firing (K0.5xBi1–0.5x)(MoxV1–x)O4 Ceramics with Scheelite Related Structure

In the present work, the (K(0.5x)Bi(1-0.5x))(Mo(x)V(1-x))O(4) ceramics (0≤x ≤ 1.00) were prepared via the solid state reaction method and sintered at temperatures below 830 °C. At room temperature, the BiVO(4) scheelite monoclinic solid solution was formed in ceramic samples with x < 0.10. When x lies between 0.1-0.19, a BiVO(4) scheelite tetragonal phase was formed. The phase transition from scheelite monoclinic to scheelite tetragonal phase is a continuous, second order ferroelastic transition. High temperature X-ray diffraction results showed that this phase transition can also be induced at high temperatures about 62 °C for x = 0.09 sample, and has a monoclinic phase at room temperature. Two scheelite tetragonal phases, one being a BiVO(4) type and the other phase is a (K,Bi)(1/2)MoO(4) type, coexist in the compositional range 0.19 < x < 0.82. A pure (K,Bi)(1/2)MoO(4) tetragonal type solid solution can be obtained in the range 0.82 ≤ x ≤ 0.85. Between 0.88 ≤ x ≤ 1.0, a (K,Bi)(1/2)MoO(4) monoclinic solid solution region was observed. Excellent microwave dielectric performance with a relative dielectric permittivity around 78 and Qf value above 7800 GHz were achieved in ceramic samples near the ferroelastic phase boundary (at x = 0.09 and 0.10).

Ferroelectric property of (Ba,Bi)(Ti,M)O3 (M; Cu, Mn, Al, Fe, In, Y, Yb) ceramics

Two types of solid solutions, (Ba1-2xBi2x)(CuxTi1-x)O3 (x ≤ 0.04) and (Ba1-xBix)(MxTi1-x)O3 (M; Al, Mn, Fe, In, Y, Yb; x ≤ 0.03) were prepared by conventional high temperature reaction. For the solid solution of (Ba1-2xBi2x)(CuxTi1-x)O3 single phases with the tetragonal cell was obtained in the region of x ≤ 0.04 and for the solid solutions of (Ba1-xBix)(MxTi1-x)O3 (M; Al, Mn, Fe, In, Y, Yb) single phases with the tetragonal cell was observed in the region of x ≤ 0.03 except the sample of M = Al in which a small amount of the second phase was contained. In these solid solutions the Tc increased with the value of x except for M = Al, and was 144.7°C for x = 0.020 of M = Cu, and the highest Tc was observed for x = 0.020 of every M atom and the order of the highest Tc was Cu (144.7°C), Y (141.4°C), Yb (140.8°C), In (138.5°C), Mn (135.5°C) and Fe (131.3°C). The highest apparent piezoelectric constant, (d33 = 258 pm/V) in these solid solutions was observed for x = 0.010 of Al.

A Study on the Properties of Substituted Ferrite (Fe-Al-Ga-Si)

Abstract The crystal structure and magnetic properties of a new solid solution type ferrite (Fe 2 O 3 ) 5 -(Al 2 3 3.4 -(Ga 2 3 0.6 -SiOwere investigated using X-ray diffraction and Mossbauer spectroscopy. The results of the X-ray diffraction pattern indicated thatthe crystal structure of the sample appears to be a cubic spinel type structure. The lattice constant (a = 8.317 A) decreasesslightly with the substitution of Ga 2 O 3 even though the ionic radii of the Ga ions are larger than that of the Al ions. The resultscan be attributed to a higher degree of covalency in the Ga-O bonds than in the Al-O and Fe-O bonds, which can also beexplained using the observed Mossbauer parameters, which are the magnetic hyperfine field, isomer shift, and quadrupolesplitting. The drastic change in the magnetic structure according to the Ga ion substitution in the (Fe 2 O 3 ) 5 (Al 2 O 3 ) 4-x (Ga 2 O 3 ) x SiOsystem and the low temperature variation have been studied through a Mossbauer spectroscopy. The Mossbauer spectrum atroom temperature shows the superpositions of two Zeeman patterns and a strong doublet. It shows significant departures fromthe prototypical ferrite and is comparable with the diluted ferrite. The doublet of spectrum at room temperature appears tooriginate from superparamagnetic clusters and also the asymmetry of the doublet appears to be caused by the preferredorientation of the crystallites. The Mossbauer spectra below room temperature show various complicated patterns, which canbe explained by the freezing of the superparamagnetic clusters. On cooling, the magnetic states of the sample were various andmulti critical. Key words nonstoichiometric ferrite, superparamagnetic clusters, Zeeman pattern, Mossbauer spectroscopy, X-ray diffraction.

Near Heterosite Li0.1FePO4 Phase Formation as Atmospheric Aging Product of LiFePO4/C Composite. Electrochemical, Magnetic and EPR Study

Freeze-drying method was employed in order to synthesize a LiFePO4/C composite. This method produced phosphate nanoparticles (10–20 nm size) covered in a carbon network. Nanostructuring and homogeneous conductive web around the active material promoted a good electrochemical response, with 141 mAh · g−1 at C/1 and a capacity retention of 90% up to 300 cycles. However, XRD measurements showed the presence of an approximately 30% of a near heterosite Li0.1FePO4 intermediate phase in the initial sample, as a product of atmospheric aging. EPR spectrum displayed a very broad signal attributed to a high spin Fe3+ ion magnetically coupled to Fe2+, confirming the formation of the non stoichiometric LixFePO4 compound. Electrochemical measurements indicated the presence of active Fe3+ in the initial composite, in a structural environment close to that of a FePO4 heterosite system. A post-mortem cathode, stopped at 4 V, was characterized. Metastable LixFePO4 solid solution type phase was not noticed. Thus, it would have disappeared during cathode cycling life, and all active material would have evolved to a classic biphasic system.

Relaxation dynamics, microwave absorption, and secondary periodicity in properties of rare-earth-modified bismuth ferrites

Based on an analysis of the structure and physical properties of bismuth ferrite (BiFeO3) modified by rare-earth (RE) elements, solid solutions characterized by the presence of spontaneous magnetization, low- and high-temperature relaxation, and maximum microwave absorption have been found. It is established that these materials exhibit a secondary periodicity in their properties. The observed effects are related to the appearance of symmetry phase transitions, specific features of the crystal chemistry of RE elements, and changes in the type of solid solutions.

Piezoelectric Behavior Based on Mixing-Doped in Lead Zirconate Titanate Ceramics and Application

In this investigation, we extend our previous works to improve piezoelectric properties of Pb(Zr,Ti)O3 ceramics. Modified lead zirconate titanate (PZT) piezoceramics with a composition Zr/Ti=53/47 containing a trace of mixing dopants were prepared by conventional ceramic technology sintering powder compacts. Replacement of (Zr, Ti)+4 by Nb+5, Pb+2 by Sb+3 and Mn+4 in PZT perovskite type solid solutions was accomplished by the creation of cation and anion vacancies. Modified ceramics were explored as a function of firing temperature to acquire exceedingly good piezoelectric characterizations. From the analysis results, calcined at 850°C for 2 h, and then sintered at 1280°C for 2 h, PZT piezoceramic showed the larger dielectric constant er 2013, mechanical quality factor Qm 120 and maximum electromechanical coupling factor kp 0.67. Besides, the bulk ceramic grains distribution were found to be uniform. Furthermore, the sample was found to possess piezoelectric properties, the resonance frequency being about 200 KHz suitable for acoustic sensor.

Fabrication of Ni, Pt, Pt/Ni Nano Powders using Wire Explosion Process and Characterization

Spherical typed Pt, Ni and Pt/Ni nanoparticles less than 50nm in particle size were successfully obtained by pulsed wire explosion in D.I. water. The Pt nanoparticles exhibited high purity, but the Ni nanoparticles exhibited a partial and very thin oxide layer. It was confirmed that the obtained Pt/Ni nanoparticles consisted of Pt and Ni nanoparticles as well as PtNi composite nanoparticles of solid solution type.

Preparation and characterization of La 9.33Si 6O 26 powders by molten salt method for solid electrolyte application

Lanthanum silicate La 9.33Si 6O 26 (LSO) powders with more uniform particle and less agglomeration were obtained at a much lower synthesis temperature by the molten salt method than by the solid-state method. LSO ceramic electrolytes were prepared with these powders and characterized as well. The optimal molten salt synthesis conditions are mass ratio of reactants to NaCl of 1:3 and synthesis temperature of 900 °C. XRD results showed that when the mass ratio of reactants to NaCl was no more than 1:3, pure LSO phase powder was obtained at 900 °C. XRD and XRF results showed that when synthesis temperature was higher than 900 °C, a solid solution type LSO powder with Na replacement for La formed at a fixed mass ratio of reactants to NaCl of 1:3. The involvement of Na in LSO lattice might lead to the lattice contraction in powders and deteriorate the conductance of ceramic electrolytes. The ceramic electrolytes prepared from the pure LSO powder via molten salt process exhibited better electrical properties than those from the powder via solid-state method.

Microwave Dielectric Ceramics with Rare-Earth (II)

Nearly half of the microwave dielectric materials includes rare-earth elements based on a database presented by Sebastian MT. The presence of rare-earth elements helps to improve the microwave dielectric properties which come from the crystal structure adjusted by the ionic radius of rare-earth. The microwave dielectrics are grouped by the crystal structure: (1) pseudo-tungstenbronze type solid solutions Ba6–3x R 8+2x Ti18O54, (2) homologous compounds Ba n La4Ti3+n O12+3n , (3) green phases Y2BaCu2O5, (4) aeschynite LaYTiO6 and scheelite BaWO4, (5) perovskite-type compounds ABO3, (6) garnet compounds A 3 B′2 B″3O12. The materials group (1)-(2) are presented in “Microwave Dielectric Ceramics with Rare-earth (I)”. In this paper we discuss the groups (3)-(6).

Synthesis of Gallium-Aluminum Dawsonites and their Crystal Structures

Solid solutions of dawsonites, ammonium aluminum carbonate hydroxide–ammonium gallium carbonate hydroxide, were obtained by the addition of aqueous solutions of mixtures of aluminum and gallium nitrates to an excess ammonium carbonate solution. The dawsonite solid solutions were calcined at 700°C to give γ-Ga2O3–Al2O3 solid solutions. The structures of these two types of solid solution were discussed on the basis of their X-ray diffraction patterns and X-ray absorption fine structure spectra.

Oxide ionic conductivity and crystallographic properties of tetragonal type Bi2O3-based solid electrolyte doped with Ho2O3

In the present work, the authors have investigated the binary system of (Bi2O3)1–x(Ho2O3)x. For the stabilisation of the tetragonal type solid solution, small amounts of Ho2O3 were doped into the monoclinic Bi2O3 via solid state reactions in the stoichiometric range 0·01≤x≤0·1. The crystal formula of the formed solid solution was determined as Bi(III)4–4xHo(II)4xO6–2xVo(2+2x) (where Vo is the oxide ion vacancy) according to the XRD and SEM microprobe results. In the crystal formula, stoichiometric values of x were 0·04≤x≤0·08, 0·03≤x≤0·09, 0·02≤x≤0·09 and 0·04≤x≤0·09 for annealing temperatures at 750, 800, 805 (quench) and 760°C (quench) respectively. The four probe electrical conductivity measurements showed that the studied system had an oxide ionic type electrical conductivity behaviour, which is increased with increasing dopant concentration and temperature. The obtained solid electrolyte system has an oxygen non-stoichiometry characteristic, and it contains O2– vacancies, which have disordered arrangements in its tetragonal crystal structure. The increase in the amount of Ho2O3 doping and temperature causes an increasing degree of the disordering of oxygen vacancies and a decrease in the activation energy Ea.

Synthesis and Characterization of the Ba&lt;sub&gt;5&lt;/sub&gt;(P&lt;sub&gt;x&lt;/sub&gt;As&lt;sub&gt;1-x&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;Cl Solid Solutions

A series of arsenate substituted chlorapatite was directly prepared through aqueous precipitation method. Characterization studies from elemental analysis, XRD, FT-IR spectra and SEM confirmed the forming of the arsenate/phosphate chlorapatite solid solutions. The XRD analysis indicated the typical solid solution phase of the apatite-type structure. In FT-IR spectra, the area of the phosphate peak was gradually suppressed and the arsenate peak increased as the proportion of the arsenate increased. The solids with As/(As+P) molar ratio of 0.49~1.0 were needle-like crystals; those with As/(As+P) molar ratio &lt;0.19 were large tabular.

Effect of nitrogen flow ratios on the structure and mechanical properties of (TiVCrZrY)N coatings prepared by reactive magnetron sputtering

This study reports the influence of growth conditions on the characteristics of (TiVCrZrY)N coatings prepared by reactive magnetron sputtering at various N 2-to-total (N 2 + Ar) flow ratio, which is R N. The crystal structures, microstructure, and mechanical properties for different R N were characterized by electron spectroscopy for chemical analysis, X-ray diffraction, atomic force microscopy, field-emission-scanning electron microscopy, transmission electron microscopy, and nanoindentation. The results indicate that the TiVCrZrY alloy and nitride coatings have hexagonal close-packed (hcp)-type and sodium chloride (NaCl)-type solid–solution structures, respectively. The voids in the coatings are eliminated and the growth of the columnar crystal structures is inhibited along with an increasing R N. As a consequence, highly packed equiaxed amorphous structures with smooth surfaces are formed. The coatings accordingly achieved a pronounce hardness of 17.5 GPa when R N = 100%.

Significant Improvement of LiNi0.8Co0.15Al0.05O2 Cathodes at 60 ° C by SiO2 Dry Coating for Li-Ion Batteries

The cycling performance of a cathode at was substantially improved by direct dry coating. The -coated cathode was obtained from firing of the mixture consisting of nanoparticles and the cathode powders with a weight ratio of 99:1 at for 5 h. The first discharge capacity of the coated cathode was 172 mAh/g, whereas the uncoated one showed 182 mAh/g at . However, the coulombic efficiency of the coated sample was 95%, which was 2% higher than that of the uncoated sample. Moreover, the discharge capacities of the coated cathode at was about 2.5 times larger than those of the uncoated sample at rates of 0.5 and 1C, showing 146 and 109 mA/g, respectively. This capacity improvement at is related to the fact that the highly distributed Si element near the surface, as a type of solid solution with , diminishes the side reactions of the cathode and electrolyte at .

Mössbauer study of modified iron-molybdenum catalysts for methanol oxidation

The preparation and catalytic properties of mixed Fe-Mo-W catalysts toward methanol oxidation are investigated. Mössbauer spectroscopy, X-ray diffraction and chemical studies revealed the formation of two types of solid solutions with compositions Fe2(MoxW1-xO4)3 and (MoxW1-x)O3. The solid solutions formed are characterized by high activity and selectivity upon methanol oxidation and are of interest in view of their practical application. Sodium-doped iron-molybdenum catalysts are also investigated and the NaFe(MoO4)2 formation was established.

Oxide Ion Conduction via Interstitial Sites in the Substituted Scheelite- and Spinel-type Oxides

In the purely academic interests to find new and high oxide ion conductors, we investigated on the electrical conduction in the substituted scheelite- and spinel-type oxides. In the former, the substitution methods shown by Pb1−xLnxWO4+x/2 and Pb1−xLn2x/3WO4 (Ln: Lanthanoid element) to intend to increase the concentration of defects brought about formation of the PbWO4-based scheelite-type solid solutions, where the enhanced oxide ion conductivities were observed compared with that of the based material. From the structural and density measurements, the charge carriers in those phases were considered to be interstitial oxide ions. On the other hand, electrical conduction was also studied in many substituted spinel type oxides. Although the oxide ions would be generally hard to move considering from their cubic-packed form, the enhanced oxide ion conductivities were observed in the inverse spinel type solid solutions based on Zn2TiO4. A typical sample was Zn2−x/2Ti1−xTaxO4, the ionic conduction of which was considered to be due to the interstitialcy oxide ion migration. These results are mentioned in relation to the defect crystal phases.