Electroconductivity of Solid Solutions Cs3–2x M x PO4 (M = Ba, Sr, Ca, Mg)

Solid solutions Cs_{3 – 2x} M _x PO₄ (M = Ba, Sr, Ca, Mg) are synthesized and their thermal behavior and electroconductivity are examined. Adding elements of Subgroup IIA of the periodic table into cesium orthophosphate shifts the phase transition, which occurs in pure Cs₃PO₄ at 450–620°, towards lower temperatures and raises the cesium cation conductivity at low temperatures. The electroconductivity of a high-temperature modification of Cs₃PO₄ is weakly dependent on the presence and concentration of such additives, which points to structural disordering of the cesium sublattice.     

Electroconductivity of Solid Electrolytes in the Systems K3–2x M x PO4 (M = Ca, Sr, Ba)

Solid electrolytes K_{3 – 2x} M _x PO₄ (M = Ca, Sr, Ba) are synthesized and the temperature and concentration dependences of their electroconductivity are studied. Adding calcium and strontium stabilizes the high-temperature -form of K₃PO₄ at room temperature, while barium-containing solid electrolytes undergo an eutectoid decomposition below 430°C. Maximum electroconductivity is exhibited by K_{3 – 2x} Sr _x PO₄ (7.1 × 10^–3 and 1.25 × 10^–1 S cm^–1 at 300 and 700°C).     

Synthesis and Ionic Conductivity of LiZr2(VO4)x(PO4)3 – x

Russian Journal of Electrochemistry - Vanadate phosphates LiZr2(VO4)x(PO4)3 – x are synthesized by the sol-gel technique with subsequent annealing and studied using X-ray diffraction...     

Solid electrolytes with potassium cation conductivity in K1−2x M x AlO2 (M = Ba, Pb) systems

New solid electrolytes with high potassium cationic conductivity based on potassium monoaluminate were synthesized and studied in the K_1?2x Ba _x AlO₂ and K_1?2x Pb _x AlO₂ systems. A partial substitution of potassium cations with double charged positive cations results in a considerable increase in the conductivity of KAlO₂ in the whole studied range of temperatures. The electric characteristics are somewhat higher in the bariumcontaining system, which is in all probability connected with the effect of the size factor: the size of the Ba²⁺ ion is higher than that of Pb²⁺, which must correlate with the increase of the effective dimensions of the migration channels in the electrolyte structure. The main cause of the conductivity increase at the introduction of the studied additives is the formation of potassium vacancies at the substitution of 2K⁺ → Ba²⁺(Pb²⁺) + V′_K.     

Sol-gel synthesis and structure of MZr2(AsO4)3 arsenates and MZr2(AsO4) x (PO4)3 − x arsenate phosphates (M = K,Rb, Cs)

MZr₂(AsO₄)₃ arsenates and MZr₂(AsO₄) _x (PO₄)_{3 ? x} arsenate phosphates (M = K, Rb, Cs) have been obtained by sol-gel synthesis followed by heat treatment and have been characterized by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Continuous series of substitutional solid solutions form in the MZr₂(AsO₄) _x (PO₄)_{3 ? x} systems (0 ≤ x ≤ 3). The solid solutions have a kosnarite structure (KZr₂(PO₄)₃, space group \(R\bar 3c\) ). The crystal structures of MZr₂(AsO₄)₃ and MZr₂(AsO₄)_1.5(PO₄)_1.5 have been refined by full-profile analysis. The structural frameworks of these phases are built from ZrO₆ octahedra and AsO₄ tetrahedra or (As,P)O₄ tetrahedra statistically populated by arsenic and phosphorus atoms. The alkali metal atoms occupy extraframework sites. The effect of the crystal chemical properties of alkali metals on the formation of the structures of MZr₂(AsO₄)₃ arsenates (M = Li-Cs) and MZr₂(AsO₄) _x (PO₄)_{3 ? x} solid solutions is discussed.     

Co-cation Conduction in Solid Solutions (K1 – xRbx)4P2O7–M2P2O7(M = Ca,Sr, Cd,Ba): Dependence on the Nature and Concentration of Cations M2+

Solid solutions of the structure -K₄P₂O₇, which have the composition (K_{1 – x} Rb _x )_3.8M_0.1P₂O₇(M = Ca, Sr, Cd, Ba) and (K_{1 – x} Rb _x )_{4 – 2y} Ca _y P₂O₇(y= 0.025–0.20), are synthesized. The solutions' electroconductivity is studied in the temperature range 400–600°C. The concentration dependences of the conductivity and the activation energy for conduction have extremums at x 0.6, which points to the polyalkaline effect. The effect increases with decreasing radius of cation M²⁺and with increasing concentration of calcium cations, which is explained by an increased energy nonequivalence of positions in the cation sublattice accessible to alkali ions.     

Lithium-cation Conduction and Crystallochemical Features of Solid Solutions La2/3 – x Li3x□4/3 – 2x Nb2O6 with the Structure of Fault Perovskite

Transport properties and crystallochemical features of lithium-containing lanthanum metaniobates La_{2/3 – x} Li_{3x4/3 – 2x} Nb₂O₆ with the structure of fault perovskite are studied. The materials studied have high conductivity by lithium ions. A correlation between the conductivity magnitude, chemical composition, and crystallographic parameters is found.     

Co-cation Conduction in Solid Solutions (K1 – xRbx)4P2O7–M2P2O7(M = Ca,Sr, Cd,Ba): Transport Numbers and Partial Ionic Conductivities

Transport numbers for potassium and rubidium cations in solid electrolytes (K_{1 – x} Rb _x )_3.8M_0.1P₂O₇(M = Ca, Cd, Ba) are measured, and the co-cation nature of the electrolytes" conduction is confirmed. The concentration dependences of transport numbers are used to draw a conclusion about the ratio between mobilities of potassium and rubidium cations. The presence of an extremum in the concentration dependence of the activation energy for the rubidium-cation constituent of conduction is confirmed by the NMR method. The obtained results are explained by assuming that the polyalkaline effect is largely due to an ordering of mobile alkali cations.     

Superacid Univalent Metal Phosphites (MH2PO3)2· H3PO3 (M = Rb,Tl(I)) and MH2PO3· H3PO3(M = K,Cs): Synthesis and Structure

By reacting the K, Rb, Cs, or Tl carbonates with excess phosphoric acid, crystals of superacid phosphites, namely, (RbH₂PO₃)₂· H₃PO₃(I), (TlH₂PO₃)₂· H₃PO₃(II), KH₂PO₃· H₃PO₃(III), -CsH₂PO₃· H₃PO₃(IV), and -CsH₂PO₃· H₃PO₃(V), were synthesized. Their structures were determined by single-crystal X-ray diffraction analysis at 150 K. Crystals I: triclinic system, space group , a= 7.713(2) Å, b= 8.679(3) Å, c= 9.235(3) Å, = 79.36(3)°, = 67.60(2)°, = 88.13(3)°, R ₁= 0.0252; crystals II: triclinic system, space group , a= 7.690(3) Å, b= 8.494(3) Å, c= 9.292(4) Å, = 79.48(3)°, = 66.72(3)°, = 85.45(3)°, R ₁= 0.0485; crystals III: monoclinic system, space group P2₁/c, a= 8.726(3) Å, b= 12.182(4) Å, c= 6.354(2) Å, = 104.14(3)°, R ₁= 0.0241; crystals IV: orthorhombic system, space group P2₁2₁2₁, a= 6.033(1) Å, b= 6.444(1) Å, c= 18.345(4) Å, R ₁= 0.0172; crystals Vare monoclinic, space group C2/c, a= 9.990(3) Å, b= 12.197(4) Å, c= 6.866(2) Å. = 118.14(3)°, R ₁= 0.0181. The hydrogen bonding systems form corrugated bands (Iand II), bent layers (III), individual tubes with rectangular cross sections (V), or a three-dimensional framework (IV). A comparative analysis of the crystal structures of acid phosphites with different compositions was performed.     

Phosphates M 0.5(1 + x) 2+ Cr x Ti2 − x (PO4)3: Synthesis, structure, and catalytic properties

Complex phosphates of titanium, chromium, and metals(2+) of the general formula M_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ (M = Mg, Ca, Mn, Ni, Sr, Ba, and Pb) were synthesized. Their phase formation was studied by means of X-ray powder diffraction, electron probe microanalysis, differential thermal analysis, and IR spectroscopy. Individual phases and solid solutions crystallizing in kosnarite and langbeinite structure types were identified; their crystallographic parameters were calculated. The catalytic properties of phosphates Ca_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ in methanol conversion were studied.     

α-Na3M2(PO4)3 (M = Ti, Fe): absolute cationic ordering in NASICON-type phases

The structure of the fully ordered α-Na(3)Ti(2)(PO(4))(3) NASICON compound was elucidated using high-quality single-crystal data. The cation/vacancy distribution forms a homogeneous 3D arrangement and could represent the absolute cationic ordering available in the full Na(3)M(2)(PO(4))(3) series, as verified for M = Fe. For M = Ti, the reversible α → γ transition was observed at 85 °C, leading to the standard disordered R ?3c γ model. Through JPDF analysis, the most probable Na(+) zigzag M(2)-M(1) diffusion scheme was directly deduced using our accurate crystallographic data.     

Comparative Research of Influence of Temperature (20-1000°C) on Binary Mixtures of Solid Solutions Mg 3 (PO 4 ) 2 ·8H 2 O with Sulphate of Differentiated Cation Compound (Na + , Ca 2+ , Al 3+ )

We analyzed thermal (20-1000;C) phase changes of the substrates of Mg 3 (PO 4 ) 2 ;8H 2 O (I), Al 2 (SO 4 ) 3 ;16H 2 O (II), CaSO 4 ;2H 2 O (III), Na 2 SO 4 (IV) and their binary mixtures (percentage ratio 10-90;) in the presence of magnesium phosphate (I). Thermal differential analysis, IR and XR, showed that these substances, heated for 1 hour up to 500 and 1000;C, changed the structure.     

Potassium-conducting solid electrolytes in the K3 − 2x Cd x PO4 system

New potassium-conducting solid electrolytes of the K_{3 ? 2x} Cd _x PO₄ system are synthesized and studied. A wide range of solid solutions reaching x ≈ 0.35 with the structure of high-temperature modification of potassium orthophosphate forms in the system. An addition of cadmium ions leads to an abrupt increase in the K₃PO₄ conductivity due to the formation of potassium vacancies. The highest conductivity is approximately 10^?2 S cm^?1 at 300°C and above 10^?1 S cm^?1 at 700°C.     

[M(dap)3]2(Sb2Se5)·xH2O(M=Ni,x=2;M=Zn,x=0)的溶剂热合成及晶体结构

利用溶剂热法合成了2种新的有机杂化锑硒化合物[Ni(dap)3]2(Sb2Se5)].2H2O(1)和[Zn(dap)3]2(Sb2Se5)](2)(dap=1,2-丙二胺),单晶X射线衍射分析结果表明,1属于三方晶系,P3121空间群,晶胞参数为a=10.7574(14),b=10.7574(14),c=31.672(4),γ=120.00°,z=4。2属于单斜晶系,P21空间群,晶胞参数为a=10.772(2),b=16.391(3),c=11.704(2),β=100.912(4)°,z=4。在2种化合物中,Ni2 与Zn2 离子分别与3个dap配体螯合形成畸变八面体几何构型,其中dap配体的N原子是无序的,而二聚[Sb2Se5]2-阴离子是由2个SbSe3三角锥共用1个Se原子连接而成。     

LiTi2(PO4)3的Na/Li离子交换特征

锂离子传导材料LiTi₂(PO₄)₃能在LiCl水溶液中高选择性地与Na⁺进行离子交换. 研究了NaCl 溶液中LiTi₂(PO₄)₃上的Na/Li离子交换反应, 实验结果表明, 升高温度能显著提高LiTi₂(PO₄)₃上的Na/Li交换反应速率, 其离子交换动力学规律可近似由JMAK(Johnson-Mehl-Aurami-Kalmogorav)方程描述. 对LiTi₂(PO₄)₃在水和NaCl溶液中的溶解行为的研究结果表明, 升高温度能加快其在水中的溶解速率, pH值过大或过小及离子交换都会加剧LiTi₂(PO₄)₃的溶解.     

Electroconductance of single-crystal Li2 + x Fe 2 − 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22)

Electrophysical properties of single-crystal Li_{2 + x} Fe _{2 ? 2x} ²⁺ Fe _x ³⁺ (MoO₄)₃ (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10^-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li_2.22Fe _1.56 ²⁺ Fe _0.22 ³⁺ (MoO₄)₃ is markedly anisotropic.     

MAlH4(M=Li,Na)储氢材料*

氢能是一种新型的清洁能源,有望替代碳经济,而氢的储存是氢能应用的关键。近年来,研究集中在具有储氢容量高和可逆性好等优点的固态储氢材料上。许多新型储氢材料不断出现,其中以MAlH₄(M=Li, Na)为代表的金属复合氢化物体系被认为是最有前景的储氢材料之一。本文综述了MAlH₄(M=Li, Na)作为可逆储氢材料的研究现状,主要从吸放氢反应、储氢性能、反应机理、理论计算和存在的问题等方面进行了讨论,并指出其相关发展趋势。     

Synthesis of Calcium Phosphates by PO(OH)x(OBut)3−x and CaO2C2H4

In this work, an alkoxide solution route to synthesize Ca phosphates was developed. For the precursors, a CaO₂C₂H₄ solution was prepared by dissolving Ca metal powder into ethylene glycol, and a PO(OH)_x(OBut)_3–x solution was prepared by dissolving P₂O₅ inton -butanol under reflux conditions. In order to obtain a mixed solution of the two precursors, acetic acid was used as an additive. The experimental results show that (1) -2CaO · P₂O₅, -3CaO · P₂O₅, and hydroxyapatite can be easily synthesized by converting the corresponding mixed solutions to powder products in a hot plate, and calcining the as prepared products at 1100°C; (2) acetic acid behaves as a good agent for controlling the reactions between the two precursors by modifying the CaO₂C₂H₄ species in solution and decreasing the reactivity of the PO(OH)_x(OBut)_3–x species.