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.     

Electroconduction of Solid Solutions Na3 – 2x M x PO4(M = Cd, Pb)

In the sodium-orthophosphate-based solid solutions in Na_{3 – 2x} M _x PO₄ systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x 0.4 for M = Cd and x 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10^–3 and 2.5 × 10^–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na₃PO₄-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect.     

Phase equilibria in the system Rb3PO4–Ba3(PO4)2

The system Rb₃PO₄–Ba₃(PO₄)₂ was investigated by thermoanalytical methods, X-ray powder diffraction, ICP, and FT-IR. On the basis of the obtained results its phase diagram was proposed. For this system with one intermediate compound, BaRbPO₄, we found that this compound melts congruently at 1700 °C, exhibits a polymorphic transition at 1195 °C and is high-temperature unstable. Also, the intermediate compound was subject to gradual decomposes to Ba₃(PO₄)₂ (the solid phase) and vaporization (with conversion of phosphorus and rubidium oxides into vapor phase). We also found that Rb₃PO₄ melts congruently at 1450 °C and shows a polymorphic transition at 1040 °C. Regarding Ba₃(PO₄)₂, we have confirmed that it melts congruently at 1605 °C and exhibits a polymorphic transition at 1360 °C.     

Eu2+在M3La3(BO3)4(M=Ca,Sr,Ba)中的发光性质

本文研究了Eu²⁺离子在M_yAl_xBO_y+3/2(1+x)(M=Ca,Sr,Ba)基质中的发光性质及磷和卤素对发光的影响。 采用以H₂和N₂混合气体为还原气氛在高温下进行固相反应的方法合成了一系列磷光体。发现,在CaAl_xBO_2.5+3/2x基质中,当X在0.5～2的范围内时及在Sr_yAl₂BO_{4 6+}基质中,当y在2～6的范围时掺入的Eu³⁺不能被H₂还原为Eu²⁺。其他Eu²⁺激活的磷光体一般都产生f～d跃迁的宽带发射,发射峰的波长随着基质组成的不同可在400～600nm的区间的变化。     

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.     

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.     

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.     

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.     

Anodic Dissolution of Aluminum in Liquid Electrolytes MF· 2AlEt3 (M = Na,K, Rb)

The kinetics of anodic dissolution of aluminum films electrodeposited on platinum via direct aluminum electrooxidation without preliminary discharge of electrolyte components is studied. The process probably involves adatoms and clusters Al* on the electrode surfaces, with limiting stage Al* – e (A1⁺)_ads.     

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.     

MMgF4(M=Ca,Sr, Ba)体系中Eu和Tb的电荷迁移

于不同气流中, 合成了MMgF4:xEu,yTb复合氟化物磷光体。该体系中Eu^3^+和Eu^2^+共存。Tb的存在影响Eu的价态存在形式。ESR测试表明, 随Tb的掺入浓度增加, Eu^2^+的浓度呈规律性变化。随Eu的掺入, 样品的XPS谱中出现了四价铽的Tb3d5/2特征伴峰。认为Eu^3^+和Tb^3^+之间存在电荷迁移平衡。即Eu^3^++Tb^3^+=Eu^2^++Tb^4^+。通过半定量手段研究了SrMgF4中这一衡的平衡常数。     

Study of the paramagnetic centers in heterofullerides MnM′3-nC60 (M = K, Rb, Cs; M′ = Be, Mg, Ca, Ba; n = 1, 2)

New heterofullerides Cs₂MC₆₀, CsM₂C₆₀, Rb₂MC₆₀, K₂MC₆₀, and KM₂C₆₀ (M = Be, Mg, Ca, Ba) have been synthesized; the temperature dependences of the magnetic susceptibilities of these compounds in the temperature range from 4.2 to 297 K have been measured. Among these heterofullerides, K₂MgC₆₀, KMg₂C₆₀, K₂CaC₆₀, K₂BeC₆₀, and Rb₂BeC₆₀ pass to the superconducting state at temperatures T _c = 13–24.3 K. The paramagnetic electronic states of the compounds have been studied by EPR at temperatures of 105–300 K, which shows the existence of two types of paramagnetic centers, related to oxygen defects and conduction electrons.     

Gas-Phase Reactions of hydrated alkaline earth metal ions, M2+(H2O) n (M = Mg, Ca, Sr, Ba and n = 4–7), with benzene

Gas-phase reactions of hydrated divalent alkaline earth metal ions and benzene were investigated by electrospray ionization Fourier-transform mass spectrometry. Rate constants for solvent-exchange reactions were determined as a function of hydration extent for Mg2+, Ca2+, Sr2+, and Ba2+ clusters containing four to seven water molecules each. All of the strontium and barium clusters react quickly with benzene. Barium reacts slightly faster than the corresponding strontium cluster with the same number of water molecules attached. For calcium, clusters with four and five water molecules react quickly, whereas those with six and seven water molecules do not. Magnesium with four water molecules reacts quickly, but not when five through seven water molecules are attached. The slow reactivity observed for some of these clusters indicates that the cation-pi interaction between the metal ion and benzene is partially screened by the surrounding water molecules. The reactivity of magnesium with seven water molecules is intermediate that of the hexa- and pentahydrate and the tetrahydrate. This result is consistent with the seventh water molecule being in the outer shell and much more weakly bound. The unusual trend in reactivity observed for magnesium may be due to the presence of mixed shell structures observed previously. These results are the first to provide information about the relative importance of cation-pi interactions in divalent metal ions as a function of metal hydration extent. Such studies should also provide a model and some insight into the relative binding affinities of divalent metal ions to aromatic residues on peptides and proteins.     

MF_2-xMgF_2(M=Ca,Sr,Ba)体系中Eu~(2+)离子的光谱特性

BaMgF_4不仅是良好的压电材料,而且也是Eu~(2+)离子激活磷光体的良好基质。MF_(2-x)MgF_2(M=Ca,Sr,Ba;x=1.0,2.0)中Eu~(2+)离子的荧光发射波长随M~(2+)离子半径增大向短波方向移动;并观察到了 BaF_2-_xMgF~2(x=1.5～2.5)体系中Eu~(2+)离子的f→f跃迁尖峰发射(360nm),当x=2.0时,其发射强度最大。     

Ionic Conductivity of Composite Solid Electrolytes (C4H9)4NBF4–Al2O3

Russian Journal of Electrochemistry - Composite solid electrolytes (C4H9)4NBF4–Al2O3 are synthesized in a wide range of composition. Their thermal, structural, and conducting properties are...     

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.     

Phase equilibria in the ErPO4–K3PO4 system

The phase equilibria occurring in the ErPO₄–K₃PO₄ system were investigated by the thermal analysis, FTIR, and X-ray powder diffraction methods. On the basis of obtained results, the related phase diagram is proposed. This system includes one intermediate compound, K₃Er(PO₄)₂; the double phosphate melts incongruently at 1355 °C and occurs in two polymorphic forms; transformation β/α-K₃Er(PO₄)₂ proceeds at 420 °C. The eutectic occurs at the composition of 58.5 wt% K₃PO₄, 41.5 wt% ErPO₄ at 1317 °C.     

Effect of hydration on conductivity of Ba4La x Ca2 − x Nb2O11 + 0.5x (x = 0.5, 1, 1.5, 2) phases

Substitution of Ca by La in initial cubic double perovskite Ba₄(Ca₂Nb₂)O₁₁[VO]₁ allowed obtaining phases with a similar structure with a lower content of structural oxygen vacancies, Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} [VO]_{1 ? 0.5x} (x = 0.5, 1, 1.5, 2). The impedance technique was used to measure the temperature dependences of conductivity in the atmosphere of dry and humid air. Transport numbers determined using the EMF method in an oxygen-air and water steam concentration cells point to the predominantly hole nature of conductivity in the high-temperature region (T > 600°C) and to predominance of proton conductivity in the low-temperature region. Activation energies of hole and proton conductivity were calculated. Thermogravimetric measurements were carried out under heating from 25 to 1000°C with simultaneous mass-spectrometric determination of evolved H₂O and CO₂. The properties of the studied Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} (x = 0.5, 1, 1.5, 2) phases were compared with the earlier studied Ba_{4 ? x} La _x (Ca₂Nb₂)O_{11 + 0.5x} phases with similar lanthanum content.