Subsolidus phase equilibria and the Li5Nd4FeO10 phase in the Li2O-Nd2O3-Fe2O3 system

A survey of the subsolidus phase equilibria in the system Li₂O-Nd₂O₃-Fe₂O₃ was made at subsolidus temperatures in the range 1000-1050 °C. A ternary phase was identified. The phase is centered on Li₅Nd₄FeO₁₀, with a cubic lattice a = 11.9494 Å. The compound melts incongruently at 1105 °C. The magnetic susceptibility was measured in the temperature range 4-300 K. The compound is paramagnetic in the temperature range 150-300 K and follows the Curie-Weiss law. At about T_N = 10 K, a long-range magnetic ordering is observed.     

Formation domain and characterization of new glasses within the Tl2O-TiO2-TeO2 system

A glass-forming domain is found and studied within the Tl₂O-TiO₂-TeO₂ system. Linear and non-linear optical, thermal and mechanical characteristics were measured and/or theoretically estimated for relevant glasses, and found to be very promising for applications in non-linear optical designs. The chemical, lattice-dynamical and structural effects of the Tl₂O and TiO₂ modifiers are discussed by using the Raman spectroscopy data. It was concluded that the former modifier favours the non-linear optical properties of the glasses, whereas the latter improves their thermal and mechanical stabilities.     

光纤接头用微晶玻璃材料的相转变

通过差热分析(DTA),X射线衍射(XRD)研究、热膨胀系数(CTE)测定及扫描电镜(SEM)观察等实验手段,研究了以Li     

Ionic conductivity of Li4GeO4, Li2GeO3 and Li2Ge7O15

The ionic conductivity of polycrystalline samples of three lithium germanates: Li₄GeO₄, Li₂GeO₃, and Li₂Ge₇O₁₅, has been determined using a c techniques and complex plane analysis. Conductivities at 400°C are 8.7 × 10^?5, 1.5 × 10^?5, and $\text{1.4 × 10}{}^{\mathrm{?7}}\text{(Ω·}\text{cm}\text{)}{}^{\mathrm{?1}}$ respectively. The conductivity of Li₄GeO₄ rises appreciably in the range 700–750°C.     

Phase diagram of the LISICON,solid electrolyte system,Li4GeO4Zn2GeO4

The phase diagram of the system Li₄GeO₄Zn₂GeO₄ is fairly similar to the corresponding silicate system and contains a wide range of solid solutions that extend to either side of the composition Li₂ZnGeO₄. These solid solutions are polymorphic. The high temperature ^γII solid solutions have a crystal structure derived from that of ^γII Li₃PO₄ and a formula, Li_{2 + 2x}Zn_1?xGeO₄ : ?0.36 < x < +0.87. LISICON, x = 0.75, is one member of the ^γII solid solution series. The compositional extent of the ^γII solid solutions is temperature dependent and eg. the LISICON composition is stable as a single phase γII structure only ? 630°C. On annealing LISICON and other lithiumrich, ^γII solid solutions in the range ～100 to 600°C, various reactions occur, including 1) precipitation of Li₄GeO₄, 2) phase transition(s) to metastable low temperature, γ-derivative structure(s) and 3) atmospheric attack to give Li₂GeO₃, Li₂CO₃ and other phases. The low temperature ^βII, ^βII′ solid solutions occur over a much smaller range of compositions to either side of Li₂ZnGeO₄ and have a crystal structure derived from that of ^βII Li₃PO₄. Li₄GeO₄ forms a short range of solid solutions.     

Phase diagram of the TeO2GeO2 system

The TeO₂GeO₂ phase diagram has been investigated by X-ray phase analysis, DTA and electron microscopy. A eutectic at 67 mol% TeO₂ and 685 ± 10°C has been found. There is evidence of microscopic phase separation in some glasses.     

The solid electrolyte system,Li3PO4Li4SiO4

The phase diagram of the system Li₄SiO₄Li₃PO₄ has been studied. At subsolidus temperatures, ? 1000°C, Li₄SiO₄ forms a short range of equilibrium solid solutions between 0 and ～ 12 mole % Li₃PO₄; γ-Li₃PO₄ forms a range of equilibrium solid solutions between ～ 58 and 100% Li₃PO₄. In addition to these equilibrium solid solutions, Li₄SiO₄ forms an extensive range of metastable solid solutions containing up to ～ 60% Li₃PO₄, on quenching melts from ? 1050°C. Hence compositions around 60% Li₃PO₄, 40% Li₄SiO₄ may be prepared in two structural forms, i.e. as solid solutions of either Li₄SiO₄ or γ Li₃PO₄. Conductivity measurements show that, at these compositions, the two solid solution structures have similar, high conductivity of Li⁺ ions.     

Crystal structure of Li2 CaUF8

Compound Li₂CaUF₈ is tetragonal. The unit cell, with $\text{a}\text{=5.2290(12)}\text{A}\text{?}$,$\text{c}\text{=11.0130(18)}\text{A}\text{?}$, contains two formula units and the space group is I$\text{bar}\text{?}$m2. The crystal structure has been solved from single crystal diffractometer data by Patterson and Fourier synthesis and refined by a least-squares method. The final value of R is 0.062 for 602 reflections. The cationic distribution is the same as in the scheelite structure, with an additional cationic ordering. Moreover, we observe that the fluorine atoms are randomly distributed at two half occupied sites.     

A low-firing microwave dielectric material in Li2O-ZnO-Nb2O5 system

LiZnNbO₄ ceramic was fabricated by the conventional solid state reaction method and its microwave dielectric properties were reported for the first time. The phase structure, microstructure, and sintering behavior were also investigated. The LiZnNbO₄ ceramic could be well densified at around 950 °C and demonstrated high performance microwave dielectric properties with a low relative permittivity ~ 14.6, a high quality factor (resonant frequency/dielectric loss) ~ 47, 200 GHz (at 8.7 GHz), and a negative temperature coefficient of resonant frequency approzmiately −64.5 ppm/°C. The LiZnNbO₄ ceramic is chemically compatible with Ag electrode material at its sintering temperature. It can be a promising microwave dielectric material for low-temperature co-fired ceramic technology.     

Subsolidus phase equilibria in the RuO2-Bi2O3-ZrO2 system

Subsolidus equilibria in air in the RuO₂-Bi₂O₃-ZrO₂ system were studied with the aim of obtaining information on possible interactions between a Bi₂Ru₂O₇-based cathode and a ZrO₂-based solid electrolyte in solid-oxide fuel cells (SOFCs). No ternary compound was found in the system. The tie lines are between Bi₂Ru₂O₇ and ZrO₂, and between Bi₂Ru₂O₇ and gamma-Bi₂O₃—the ZrO₂ stabilised Bi₂O₃ phase, stable at temperatures over 710 °C.     

Phase relations of the Li2O-Ta2O5-B2O3 and Li2O-WO3-B2O3 systems and promising nonlinear optical compounds in K2O-Ta2O5-B2O3 system

The subsolidus phase equilibria of the Li₂O-Ta₂O₅-B₂O₃, K₂O-Ta₂O₅-B₂O₃ and Li₂O-WO₃-B₂O₃ systems have been investigated mainly by means of the powder X-ray diffraction method. Two ternary compounds, KTaB₂O₆ and K₃Ta₃B₂O₁₂ were confirmed in the system K₂O-Ta₂O₅-B₂O₃. Crystal structure of compound KTaB₂O₆ has been refined from X-ray powder diffraction data using the Rietveld method. The compound crystallizes in the orthorhombic, space group Pmn2₁ (No. 31), with lattice parameters a = 7.3253(4) Å, b = 3.8402(2) Å, c = 9.3040(5) Å, z = 2 and D_calc = 4.283 g/cm³. The powder second harmonic generation (SHG) coefficients of KTaB₂O₆ and K₃Ta₃B₂O₁₂ were five times and two times as large as that of KH₂PO₄ (KDP), respectively.     

Phase equilibria and curie temperature in the LiNbO3−xTiO2 system,investigated by dta and x-ray diffraction

Solidus and liquidus temperatures, ferroelectric Curie temperature and lattice parameters of phases in the congruent LiNbO₃?xTiO₂ system was determined (0 < x < 0.465). The TiO₂ phase shows solid solubility in congruent LiNbO₃ up to x = 0.20 at 1187°C. The Curie temperature of the solid solution Li_0.954 Nb_1.0092 O₃:xTiO₂ decreases substantially with increasing amounts of TiO₂. This temperature variation was expressed as a function of the equivalent composition $\text{Re}\text{=}\text{0.954}\text{0.954 + 1.0092 +}\text{x}$; it coǐncides with the Curie temperature variation of LiNbO₃ with composition, which has also been studied by DTA. Outside the solid solution range (x > 0.20) two phases are present: a LiNbO₃ — type phase and a rutile-type phase.     

Structure et conductivite electrique de verres appartenant au systeme Li2Si2O5 Li2SO4

The conductivity of vitreous electrolytes belonging to the Li₂Si₂O₅ Li₂SO₄ system has been measured over the temperature range 25–300 °C and for Li₂SO₄ concentrations varying from 0–28 mole percent. It has been found that the conductivity increases with the Li₂SO₄ fraction, attaining 10^?5 Ω^?1 cm^?1 at 130°C for the glass containing the highest proportion of sulphate. Raman spectroscopic studies indicate that the tetrahedral SO^2?₄ ions are in the glassy network, inserted or not into the silicate chains.     

Subsolidus phase equilibria in the CaO-poor part of the RuO2-CaO-SiO2 system

During firing the conductive phase based on CaRuO₃ in lead-free thick-film resistors decomposes, presumably due to interactions with the silica-rich glass phase. Subsolidus equilibria in the CaO-poor part of the RuO₂-CaO-SiO₂ diagram were studied with the aim of investigating possible interactions between the conductive phase and silica-rich glasses in thick-film resistors. The tie lines are between CaRuO₃ and CaSiO₃, and between RuO₂ and CaSiO₃. This indicates that the calcium ruthenate is not stable in the presence of the silica-rich glass phase.     

Phase relations in the CaAl2O4|CaGa2O4 system

The solid state reactions and the phase relations in the CaAl₂O₄|CaGa₂O₄ system, of which both end-members have the stuffed tridymite structure, were examined by using three kinds of starting materials; A (CaCO₃ + (Al,Ga)₂O₃), B (CaAl₂O₄ + CaGa₂O₄) and C (CaCO₃ + Al₂O₃ + Ga₂O₃). In the starting material B, a very low rate of solid state reaction between CaAl₂O₄ and CaGa₂O₄ was found, which seemed to be due to very slow interchange of Al³⁺ and Ga³⁺ located in tetrahedra of this structure. In order to obtain the probable equilibrium phase relations, it was necessary to use the starting material A. In the present system, a new phase was found in a wide range of composition as a stable phase, which was supposed to have the same structure as so-called metastable phase of CaGa₂O₄ and different array of tetrahedra from either CaAl₂O₄ or CaGa₂O₄|I.     

Low temperature biomimetic synthesis of the Li2ZrO3 nanoparticles containing Li6Zr2O7 and high temperature CO2 capture

Li₂ZrO₃ nanoparticles containing Li₆Zr₂O₇ were prepared by a biomimetic soft solution route and characterized with X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption. The results show that the tetragonal Li₂ZrO₃ nanoparticles containing monoclinic Li₆Zr₂O₇ can be obtained using this simple method. The mean diameter of the nanoparticles is approximately 90 nm and the corresponding specific surface area is 23.7 m² g^− 1. Moreover, the Li₂ZrO₃ nanoparticles obtained were thermally analyzed under a CO₂ flux to evaluate their CO₂ capture capacity at high temperature. It was found that the as-prepared Li₂ZrO₃ nanoparticles would be an effective acceptor for high temperature CO₂ capture.     

Lithium ion conduction in Li5A104, Li5GaO4 and Li6ZnO4

Polycrystalline samples of Li₅Al0₄, Li₅Ga0₄, and Li₆Zn0₄ have been synthesized, and their ionic conductivity measured over a range of temperature. These materials, which have the antifluorite structure with large concentrations of intrinsic cation vacancies, have Arrhenius-like conductivities at low temperatures, with a steep rise in the range 385–450°C, reaching very high values, with a very small temperature dependence, thereafter. Materials of this type, which exhibit the highest values of lithium ion conductivity yet found, may have important practical applications in devices such as elevated temperature batteries.     

Phase equilibria in the liquid ternary system [Th(NO3)4(TBP)2]-[UO2(NO3)2(TBP)2]-Isooctane at different temperatures

The phase diagrams of the ternary systems [Th(NO₃)₄(TBP)₂]-[UO₂(NO₃)₂(TBP)₂]-isooctane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Th(NO₃)₄(TBP)₂] and [UO₂(NO₃)₂(TBP)₂], and phase II is enriched in isooctane. With increasing temperature from 298.25 to 333.15 K, the mutual solubility of Th(NO₃)₄(TBP)₂ and isooctane does not change noticeably, but the two-phase fields somewhat contract. In the two-phase systems [UO₂(NO₃)₂(TBP)₂] is preferentially distributed in phase I, although the binary system [UO₂(NO₃)₂(TBP)₂]-isooctane is single-phase over the entire temperature range examined. The preferential accumulation of [UO₂(NO₃)₂(TBP)₂] in phase I causes the redistribution of [Th(NO₃)₄(TBP)₂] and isooctane into phases II and I, respectively. The compositions of the ternary systems in the critical points at different temperatures were determined. The electronic absorption spectra of uranyl nitrate solvate with TBP in the homogeneous and two-phase systems were recorded and analyzed. Original Russian Text ? A.K. Pyartman, V.A. Keskinov, V.V. Lishchuk, Ya.A. Reshetko, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 420–422.     

Synthesis and materials characterization of Li2MnO3-LiCrO2 system nanocomposite electrode materials

A series of Li[Cr_xLi_(1−x)/3Mn_2(1−x)/3]O₂, (0.2 ≤ x ≤ 0.4) with nanocomposite structures was synthesized by a solution method with subsequent quenching. The sample structures were investigated by X-ray diffraction (Rietveld refinement), electron diffraction and HRTEM. According to co-indexed electron diffraction patterns and HRTEM images, Li[Cr_0.211Li_0.268Mn_0.520]O₂ was found to be composed of solid solution powders and Li[Cr_0.290Li_0.240Mn_0.470]O₂ and Li[Cr_0.338Li_0.225Mn_0.436]O₂ of nanocomposite powders indexed in monoclinic and hexagonal structure. Among the three compounds, the nanocomposite Li[Cr_0.290Li_0.240Mn_0.470]O₂ cathode prevented spinel-like structural transformation during cycling and delivered a good reversible capacity of about 195 mAh/g.     

Some new non-stoichiometric ferroelectric phases appearing close to LiTaO3 in the ternary system Li2O-Ta2O5-(TiO2)2

A crystal chemical study of the Li₂O-Ta₂O₅-(TiO₂)₂ system has allowed to obtain some new solid solutions with a LiTaO₃- related structure. The investigated phases are either stoichiometric or non-stoichiometric, either through cationic excess or deficit with regard to LiTaO₃. They have all a ferroelectric-paraelectric transition. For each series the value of the Curie temperature T_C decreases when the composition deviates from LiTaO₃. T_C obtained for Li_1.14Ta_0.86Ti_0.14O₃ (T_C= 205°C) is the lowest ever obtained for this structural type. As LiTaO₃ is a good pyroelectric material; the important decrease of T_C associated with the diffuse character of the phase transition can lead to a potential interest for infrared detector applications. Moreover, the significant decrease of the melting point (T_M(LiTaO3) = 1650°C, T_M(Li1.14Ta_0.86Ti_0.14O₃) = 1460°C) is an obvious advantage for crystal growing.