RESUMO
Single crystals of four new cesium copper silicates were grown from CsCl/CsF flux. [CsCs4Cl][Cu2Si8O20] is a salt-inclusion compound that crystallizes in space group P4/m with lattice parameters a = 12.2768(3) Å and c = 8.6470(2) Å; Cs6Cu2Si9O23 crystallizes in space group P21/n with lattice parameters a = 15.0763(9) Å, b = 6.9654(4) Å, c = 26.9511(17) Å, and ß = 99.240(2)°; Cs8Cu3Si14O35 crystallizes in space group C2/c with a = 39.2236(13) Å, b = 6.9658(2) Å, c = 14.9115(5) Å, and ß = 97.1950(10)°; and Cs2CuSi3O8 is a member of the stuffed tridymite family and crystallizes in a monoclinic distortion of the CsAlSiO4 structure type with space group C2/m and a = 12.8587(3) Å, b = 5.38510(10) Å, c = 9.0440(2) Å, and ß = 133.2580(10)°. All four compounds contain CuO4-flattened tetrahedra. The degree of flattening can be correlated with the UV-vis spectra. Cs6Cu2Si9O23 exhibits spin dimer magnetism that can be attributed to super-super-exchange between two Cu(II) ions connected by a silicate tetrahedron. The other three compounds all show paramagnetic behavior down to 2 K.
RESUMO
Single crystals of A3MF6 (A = Rb, Cs; M = Al, Ga) were grown from mixed alkali chloride/fluoride fluxes in sealed silver tubes. For Cs3AlF6 and Cs3GaF6, two polymorphs were observed at room temperature: m-Cs3MF6 and o-Cs3MF6. For the two Rb containing compositions, only one room temperature polymorph was observed: o-Rb3AlF6 and t-Rb3GaF6, respectively. Simultaneous TGA/DSC and high temperature SCXRD/PXRD were used to study the high temperature behavior of A3MF6. The compounds of all four compositions were found to undergo structure transitions upon heating to the same cubic structure type, c-A3MF6.
