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Abstract: The influence of the preparation conditions and metaphosphate secondary phase on the proton conduction and chemical stability of the single and polycrystalline CsH2PO4 samples was studied by the ac admittance technique. The relation between frequency dependences of the admittance plots and adsorbed water as well as a content of the metaphosphate phase was determined. It was shown that in ambient conditions the thermal decomposition reactions start on the sample''s surface at temperatures above specific point, T 1 =425 K, and the rate of the decomposition reactions on the interfaces is strongly influenced by the sample''s quality. It is suggested that this reaction is initiated by the melting of the thin layer of CsH5(PO4)2 on the surface of CsH2PO4. The variation of the contributions of the intergrain and electrode–proton conductor boundaries to the total admittance with the temperature was studied for polycrystalline CDP samples and obtained data were compared with those for nominally pure CDP single crystal samples. [Copyright &y& Elsevier]

A new Au(Ba,La)2CuO5+δ (Au-1201) phase was synthesized at 6 GPa and 1250 °C. This compound is the first member of the Au-containing cuprate family. It crystallizes in an orthorhombic primitive cell with lattice parameters a=3.7976(3) A˚, b=3.8509(3) A˚, c=8.5749(9) A˚. Electron diffraction studies revealed the existence of additional weak reflections indicating a superlattice of as=5a, bs=b, cs=2c. A weak superconducting signal was observed below Tc=19 K in the magnetic susceptibility, but the diamagnetism was not large enough to assume bulk superconductivity. [Copyright &y& Elsevier]

Two new layered oxyborates B2Sr3.2Y1.8Cu3O12 and B2Sr3.11Ho1.89Cu3O12 have been synthesized at 6 GPa using a belt-type apparatus. These compounds could be described as intergrowth between B-1201 and B-1212 phases. The crystal structure of B2Sr3.11Ho1.89Cu3O12 has been determined using single crystal X-ray data. It was refined to R1(I>2σ(I))=0.0456, wR2(all data)=0.1044 with F2 data. B2Sr3.2Y1.8Cu3O12 and B2Sr3.11Ho1.89Cu3O12 crystallize in the space group P4/mmm (no. 123), Z=1 with a=3.852(1) A˚, c=17.770(6) A˚ and a=3.8516(4) A˚, c=17.764(2) A˚, respectively. A weak superstructure with as=a√2, bs=b√2, cs=c was deduced from an electron diffraction pattern for B2Sr3.11Ho1.89Cu3O12 probably due to local ordering of the triangular BO3 groups although such ordering was not revealed from single crystal X-ray data. [Copyright &y& Elsevier]

Single crystals of Au1+xBa2Ca2Cu3−xO9 (Au-1223) were grown at 6 GPa and 1325 °C. This phase is the third member of the Au-containing cuprate family of AuBa2Can−1CunO2n+3 and shows a weak signal of superconductivity. The crystal structure was refined to R1 (I>2σ(I))=0.0188 and wR2=0.0485 with F2 data. The Au-1223 phase crystallizes in the space group Pmmm (no. 47), a=3.8119(1) A˚, b=3.8556(1) A˚, c=15.4431(5) A˚, Z=1. Partial substitution of Au for Cu in the CuO2 planes was revealed. The Au incorporation to the conduction layers may be a reason for the suppression of superconductivity in Au-1223. [Copyright &y& Elsevier]

Single crystals were grown for new layered oxycarbonates CCa2CuO5 and CSr1.9Ca1.1Cu2O7 at 6 GPa using a belt-type apparatus. Their crystal structures were determined using single crystal X-ray diffraction data with R1(wR2)=0.0294(0.0659) and 0.0199(0.0457) for CCa2CuO5 and CSr1.9Ca1.1Cu2O7, respectively. These phases crystallize in the space group P4/mmm (No. 123), Z=1 with a=3.8157(1) A˚, c=7.1426(3) A˚ for CCa2CuO5 and a=3.8753(1) A˚, c=10.6765(5) A˚ for CSr1.9Ca1.1Cu2O7. In contrast to CSr2CuO5, no ordering in the orientation of the triangular CO3 groups was revealed in CCa2CuO5 and CSr1.9Ca1.1Cu2O7. [Copyright &y& Elsevier]