On the proton conductor (H3O)Zr2(PO4)3

The compound HZr₂(PO₄)₃ was converted to (H₃O)Zr₂(PO₄)₃ by refluxing in water for 12 or more hours. The water is lost above 150°C to regenerate the original triphosphate. The hydronium ion phase is rhombohedral with hexagonal axes of a = 8.760(1) and $\text{c}\text{= 23.774(4)}\text{A}\text{?}$. Proton conduction in these compounds was investigated by an ac impedance method over the frequency range 5Hz – 10MHz. The activation energy for (H₃O)Zr₂(PO₄)₃ in the temperature range of 25 to 150°C was 0.56eV while the corresponding value for HZr₂(PO₄)₃ (125 – 300°C) was 0.44eV.     

Etude du systeme KPO3-LaP3O9. Donnees cristal lographiques sur K2La(PO3)5 et (NH4)2La(PO3)5

The system KPO₃-LaP₃O₉ has been studied for the first time by differential thermal analysis and X ray diffraction. The system shows two compounds KLa(PO₃)₄ and K₂La(PO₃)₅ which melt in a peritectic decomposition at 880°C and 770°C respectively. An eutectic point appears at 705°C; The eutectic point corresponds to a concentration of 10% molar LaP₃O₉.Infra Red absorption spectra are typical of chain phosphates.The new compound K₂La(PO₃₅ is isotypic whith (NH₄)₂La(PO₃)₅ which has been synthetized for the first time. They belong to the triclinic system whith space group P1 and Z = 2. The parameters of the unit cell are: $\text{a = 7.309(4)}\text{A}\text{?}$$\text{b = 13.35(2)}\text{A}\text{?}$$\text{c = 7.155(7)}\text{A}\text{?}$α = 90°3(1) β = 109°17(7) γ = 89°90(4) for K₂La(PO₃)₅ and: $\text{a = 7.174(8)}\text{A}\text{?}$$\text{b = 13.38(2)}\text{A}\text{?}$$\text{c = 7.35(2)}\text{A}\text{?}$α = 90°6(2) β = 107°4(1) γ = 89°82(7) for (NH₄)₂La(PO₃)₅.     

The sodium ytterbium orthophosphate Na3(1+x)Yb(2-x)(PO4)3

A new sodium ytterbium orthophosphate with general formula Na_3(1+x)Yb_(2-x)(PO₄)₃ (0.07 ? x ? 0.50) has been prepared and characterized. Its crystal structure has been determined from a single crystal for x = 0.50. The space group is R3?c, the lattice constants are : $\text{a}\text{= 9.12(1)}\text{A}\text{?}$, $\text{c}\text{= 21.81(6)}\text{A}\text{?}$. The structure of Na_4.50Yb_1.50(PO₄)₃ is related to that of NaZr₂(PO₄)₃. The PO₄ tetrahedra and the (Yb,Na)O₆ octahedra form a three-dimensional skeleton in which the remaining sodium atoms are inserted. This structural type is also found for the phases Na_4.50Ln_1.50(PO₄)₃ (Ln = Tm, Lu) and Na_4.50Ln_1.50(AsO₄)₃ (Ln = Er, Tm, Yb, Lu).     

Preparation of sodium zirconium phosphates of the type Na1+4xZr2−x (PO4)3

Sodium zirconium phosphates of the type Na_1+4x Zr_2?x (PO₄)₃ were prepared from mixtures of Na₃PO₄-ZrO₂-ZrP₂O₇ in sealed platinum tubes at temperatures of 900 – 1200°C. Stoichiometric NaZr₂ (PO₄)₃ (x = 0) was found not to exist. Instead, a solid solution in the range x = 0.02 ? 0.06 was found, with a slight difference in unit cell dimensions obtained. A second solid solution region was found with x = 0.88 – 0.93. At still higher values of x, a stoichiometric phase with hexagonal unit cell dimensions of $\text{a}\text{= 9.152(1)}\text{A}\text{?}$ and $\text{c}\text{= 21.844(1)}\text{A}\text{?}$ was obtained. Finally a phase of composition Na₇Zr_0.5 (PO₄)₃ was synthesized at the highest values of x. Attempts to prepare Na_5+x ZrSi_x-P_3?xO₁₂ always yielded NASICON and Na₇Zr_0.5 (PO₄)₃.     

Temperature dependence of critical stress and phase diagram of ferroelastic Pb3 (PO4)2 Pb3 (VO4)2

The temperature dependence of the critical stress in ferroelastic Pb₃ (PO₄)₂ reveals a Curie-Weiß law ($\text{ß =}\text{1}\text{2}$) up to 145°C. Between 160°C and the transition point at 180°C a crossover to a $\text{ß =}\text{1}\text{3}$ regime was found. For mixed crystals Pb₃ (PO₄)₂ ? Pb₃ (VO₄)₂ a phase diagram is suggested from optical, dielectric and Raman spectroscopical experiments.     

The incommensurate solid solution phase Na5−4x Zr1+x(PO4)3:0.04 <x <0.15

The orthophosphate solid solution phase, Na_5?4x Zr_1+x(PO₄)₃:0.04 ? x ? 0.15 has trigonal symmetry with an apparent one dimensional incommensurate superstructure parallel to c_HEX. Using selected area electron diffraction patterns as a guide, an indexing scheme for the powder X-ray data has been devised. The parameter $\text{k = c}{}_{\mathrm{<mtext>supercell</mtext>}}\text{c}{}_{\mathrm{<mtext>subcell</mtext>}}$ varies smoothly with composition from ～ 10.4 at x = 0.04 to ～4.4 at x = 0.11 and is believed to originate in ordering of the extra interstitial Zr⁴⁺ ions. The Na⁺ ion conductivity increases gradually with x and for x = 0.108 varies from ～5×10^?8 ohm^?1 cm^?1 at 25°C to ～1×10^?3 ohm^?1 cm^?1 at 300°C.     

The crystal structure of a new high -Nd- concentration laser material: Na3Nd(PO4)2

The crystal structure of Na₃Nd(PO₄)₂ has been determined from three-dimensional Mo-Kα diffractometer data. The space group is Pbc2₁, the lattice constants are: $\text{a}\text{= 15.874(8)}\text{A}\text{?}$$\text{b}\text{= 13.952(8)}\text{A}\text{?}$$\text{c}\text{= 18.470(9)}\text{A}\text{?}$ and there are 24 formula units per unit cell, giving a Nd concentration of 5.8 10²¹cm^?3. The final R-factor with 2329 independent reflections is 0.060. The structure of Na₃Nd(PO₄)₂, very closely related to that of Na₃La(VO₄)₂, is made up of isolated PO₄ tetrahedra and of sodium and neodymium atoms arranged in an ordered way. The tripling of the a parameter results only from the distortion of the PO₄ tetrahedra. The NdO_y polyhedra are isolated from one another and the shortest Nd-Nd distance is 4.65 Å.     

Crystal structures of two cesium phosphate-tellurates : Te(OH)6.Cs2HPO4 and Te(OH)6.Cs2HPO4.2CsH2PO4

Te(OH)₆.Cs₂HPO₄ and Te(OH)₆.Cs₂HPO₄.2CsH₂PO₄ are monoclinic, the first one with a = 8.204(5), b = 18.416(9), $\text{c}\text{= 6.995(5)}\text{A}\text{?}$, β = 89.89(5)°, Z = 4, space group P2₁/n, the second one with a = 9.591(6), b = 13.163(9), $\text{c}\text{= 8.367(5)}\text{A}\text{?}$, β = 106.27(5)°, Z = 2, space group P2₁/m. As already observed in previously described phosphate-tellurates the main feature of these atomic arrangements is the coexistence of two independent and different types of anions (PO₄ and TeO₆ groups) in the unit cell.     

Crystal data for two new phosphate-tellurates : Te(OH)6·2TlH2PO4·Tl2HPO4 and Te(OH)6·2TlH2PO4. Crystal structure of Te(OH)6·2TlH2PO4

We describe chemical preparations and give crystal data for two new phosphate-tellurates : Te(OH)₆·2TlH₂PO₄·Tl₂HPO₄ and Te(OH)₆·2TlH₂PO₄. Both are monoclinic with the following unit cell dimensions : a = 13.68(1), b = 6.317(5), $\text{c}\text{= 11.36(1)}\text{A}\text{?}$, β = 110.18(1)°, Z = 2, D_x = 4.82, S.G. = Cm for the first one, a = 6.285(5), b = 14.74(1), $\text{c}\text{= 7.844(5)}\text{A}\text{?}$, β = 113.38(1)°, Z = 2, D_x = 4.14, S.G. = P2₁/n for the second one. Crystal structure of the second salt shows, as in the already described phosphate-tellurates, the coexistence of independent TeO₆ octahedra and PO₄ tetrahedra in the atomic arrangement.     

The crystal structure of Pb8Bi2(PO4)6O2

Single crystals of Pb₈Bi₂(PO₄)₆O₂ were grown by the Czochralski technique, and the structure of this compound was determined. It was found to crystallize in Pnma orthorhombic symmetry with a = 13.313, b = 10.284 and $\text{c}\text{= 9.219}\text{A}\text{?}$. The structure was refined to an R value of 7%. Powder diffraction data are also reported.     

Hydrogen bonding in NH4HSO4. NH4H2PO4

NH₄HSO₄·NH₄H₂PO₄ is monoclinic $\text{P}\text{2}{}_1\text{n}$ with Z = 2 and the following unit cell dimensions : a = 7.723(5), b = 7.540(5), $\text{c}\text{= 7.482(5)}\text{A}\text{?}$, β = 101.32(5)°. Crystal structure of this salt has been solved with a final R value 0.028. As in the corresponding potassium salt PO₄ and SO₄ tetrahedra are randomly distributed.A complete hydrogen bonding pattern is given.     

Diagramme d'equilibre solide-liquide du systeme Ce(PO3)3 — AgPO3

The Ce(PO₃)₃ — AgPO₃ system was investigated by differential thermal analysis (DTA) and X-ray diffraction. Its phase equilibrium diagram was established by recording heating curves on a M5 Setaram μ-DTA aparatus. This diagram shows that the Ce (PO₃)₃—AgPO₃ system forms only one compound, AgCe(PO₃)₄, which melts in a peritectic reaction at 788°C. The chemical preparation, powder diagram and main crystallogrophic characteristics of this compound are given. AgCe(PO₃)₄, a polyphosphate isotypic with NaNd(PO₃)₄, has a monoclinic unit cell with a space group $\text{P2}{}_1\text{n}$ and parameters a = 9.717(4), b = 12.959(5), c = 7.242(2) Å, β = 91.07(2)°, Z = 4, V = 911.79 ų, d_x = 4.11. The different structure types of binary poly and metaphosphates, M₂O.Ln₂O₃.4P₂O₅, are regrouped and a correlation between each crystalline form and the corresponding M³ and Ln³⁺ cation size is dicussed.     

Crystal chemistry of γ-(Zn, Me)3(PO4)2 solid solutions

A number of γ-(Zn,$\text{Me}$)₃(PO₄)₂ solid solutions with the “γ-Zn₃(PO₄)₂” structure have been prepared and equilibrated at about 1070 K ($\text{Me}\text{= Mg, Mn, Fe, Co, Ni, Cu, and Cd}$). Approximate homogeneity ranges are given. The monoclinic unit cell dimensions have been accurately determined from Guinier-Hägg photographs. The structure contains five- and six-coordinated cations. Correlations between homogeneity ranges, unit cell dimensions, cation radii and cation distributions are pointed out, and the phases are also compared with isotypic (Mg,$\text{Me}$₃(PO₄)₂ and (Co,$\text{Me}$)₃(PO₄)₂ solid solutions.     

New tetrahedrally coordinated A2CdBr4 compounds (A = Cs,CH3NH3)

(CH₃NH₃)₂CdBr₄ and Cs₂CdBr₄ are two compounds with a tetrahedral CdBr₄-coordination. Their room temperature structures are determined. (CH₃NH₃)₂CdBr₄: monoclinic, $\text{P}\text{2}{}_1\text{c}$, $\text{a}\text{= 8.1227(13)}\text{A}\text{?}$, $\text{b}\text{= 13.4355(16)}\text{A}\text{?}$, $\text{c}\text{= 11.4194(13)}\text{A}\text{?}$, β = 96.194(11) °, z = 4. Cs₂CdBr₄: orthorhombic, Pnma, $\text{a}\text{= 10.235(5)}\text{A}\text{?}$, $\text{b}\text{= 7.946(3)}\text{A}\text{?}$, $\text{c}\text{= 13.977(5)}\text{A}\text{?}$, z = 4.     

Crystal chemistry of (Cd,Me)3(PO4)2 solid solutions

A number of solid solutions of $\text{Me}$₃(PO₄)₂ in Cd₃(PO₄)₂ have been prepared and equilibrated at 1070 K ($\text{Me}\text{=}\text{Mg, Mn, Fe, Co, Ni, Cu, Zn, or Ca}$). The respective ($\text{Cd}{}_{\mathrm{<mtext>1?</mtext><mtext>z</mtext>}}\text{Me}{}_{\mathrm{<mtext>z</mtext>}}\text{)}{}_3\text{(}\text{PO}{}_4\text{)}{}_2$ phases are either isotypic with β′-Cd₃(PO₄)₂ or with the mineral graftonite, both with five- and six- (or even seven)-coordinated cations. The monoclinic unit cell dimensions have been accurately determined from Guinier-Hägg photographs, and complete X-ray powder diffraction data are given for β′-Cd₃(PO₄)₂. The cell volumes are strongly correlated to the size and amount of incorporated $\text{Me}$²⁺ cation. The homogeneity regions and structures of the (Cd,$\text{Me}$)₃(PO₄)₂ phases, though, seem rather to be controlled by the $\text{Cd}{}^{\mathrm{2+}}\text{Me}{}^{\mathrm{2+}}$ cation ordering.     

Crystal structure of KHSO4 · KH2PO4

KHSO₄ · KH₂PO₄ is monoclinic $\text{P}\text{2}{}_1\text{n}$ with Z = 2 and the following unit cell dimensions: a = 7.434(3); b = 7.341(3); $\text{c}\text{= 7.148(3)}\text{A}\text{?}$; β = 99.56(5)°.Crystal structure of this salt has been solved, using 1699 independent reflexions with a final R value: 0.034. PO₄ and SO₄ tetrahedra are randomly distributed in the arrangement with a resulting (P.S)-O mean distance of 1.508(3) Å.     

(NbSe4)3I low temperature structure

Low temperature (128 K) structural determination of (NbSe₄)₃I is reported. (NbSe₄)₃I is found to undergo a second-order displacive phase transition at 274 K. Symmetry is tetragonal, space group P4?2₁c with $\text{a}\text{= 9.450(7)}\text{A}\text{?}$$\text{c}\text{= 19.08(6)}\text{A}\text{?}$. (NbSe₄)₃I is no more centrosymmetric : NbSe₄ chains are shifted in respect of each other. Some experimental results are discussed in connection with the transition.     

Synthesis and symmetry transformation in the perovskite compounds PbHfO3 and CdHfO3

From high temperature X-ray diffraction experiments the perovskite compounds PbHfO₃ and CdHfO₃ have been shown to undergo a series of structural phase transformations. At 298°K PbHfO₃ is orthorhombic with cell dimensions $\text{a}\text{= 5.8572(5)}\text{A}\text{?}$, $\text{b}\text{= 11.689(1)}\text{A}\text{?}$, $\text{c}\text{= 4.0971(4)}\text{A}\text{?}$ and most probable space group Pnam. At 450°K it is rhombohedral with hexagonal cell dimensions $\text{a}\text{= 5.854(1)}\text{A}\text{?}$ and $\text{c}\text{= 7.145(2)}\text{A}\text{?}$ and at 520°K PbHfO₃ is cubic perovskite with $\text{a}\text{= 4.1354(4)}\text{A}\text{?}$. CdHfO₃ is also orthorhombic at 298°K with cell dimensions $\text{a}\text{= 5.5014(8)}\text{A}\text{?}$, $\text{b}\text{= 5.6607(8)}\text{A}\text{?}$, $\text{c}\text{= 7.969(1)}\text{A}\text{?}$, and space group Pbnm. At 1075°K CdHfO₃ is rhombohedral with hexagonal cell dimensions $\text{a}\text{= 5.747(4)}\text{A}\text{?}$ and $\text{c}\text{= 13.49(1)}\text{A}\text{?}$     

Crystal data on ytterbium chlorosilicate,Yb3(SiO4)2Cl

Ytterbium chlorosilicate, Yb₃(SiO₄)₂Cl, was obtained in the form of single crystals up to 1.5 × 1.5 × 0.5 mm³ as by-product of the synthesis of ytterbium oxychloride. The compound has orthorhombic symmetry (space group Pnma - D_2h¹⁶). The unit cell parameters are: $\text{a}\text{= 6.753}\text{A}\text{?}\text{, b}\text{= 17.583}\text{A}\text{?}\text{, c}\text{= 6.137}\text{A}\text{?}$. The substance is characterized by means of morphology and X-ray powder data.     

The structure of the low temperature phase Mg2NiH4(LT)

The crystal structure of a low temperature modification of Mg₂NiH₄(LT), stable below 235°C, has been determined from Guinier-Hägg powder diffraction data. The unit cell dimensions are $\text{a}\text{= 6.497(2)}\text{A}\text{?}$, $\text{b}\text{= 6.414(1)}\text{A}\text{?}$, $\text{c}\text{= 6.601(2)}\text{A}\text{?}$ and β = 93.23(2)°. The structure has been refined by profile analysis from a sample also containing MgH₂ and small amounts of two other phases, viz. the high temperature modification Mg₂NiH_3.9(HT) and Mg₂NiH_x(LT). It is indicated that the phase transformation of Mg₂NiH_3.9 (HT) at 235°C is eutectoid, giving mainly Mg₂NiH₄(LT) but also small amounts of a less hydrogen containing phase Mg₂NiH_x(LT) (x≈2).