Search

The crystal structures of Tl 2 TeBr 6 and Tl 2 Tel 6 have been determined using X-ray powder diffraction techniques. Tl 2 TeBr 6 crystallizes in the tetragonal space group P4/mnc, with the lattice parameters: a = 7.468(1) A, c = 10.682(2) A, Z = 2. Tl 2 TeI 6 crystallizes in the monoclinic space group P2 1 /c, with the lattice parameters: a = 7.765(2) A, b = 8.174(2) A, c = 13.756(5) A, β = 124.2(1)°, Z = 2. The Rietveld refinement procedures were stopped when the intensity residuals R B = 0.038 for Tl 2 TeBr 6 and R B = 0.049 for Tl 2 TeI 6 had been reached. The crystal structures of both investigated ternary halides belong to the large family of K 2 PtC 6 -related structures.

The stability regions of Rb2TeI6 , Cs2TeI6 , and Tl2TeI6 were mapped out using quantitative thermal analysis and microhardness measurements on annealed and quenched samples. The congruently melting compositions of the three compounds were shown to coincide with their stoichiometric compositions. A procedure was developed for growing Rb2TeI6 , Cs2TeI6 , and Tl2TeI6 single crystals, and some properties of the grown crystals were investigated.

The composition stability limits of the compounds Tl2TeBr6 , Cs2TeBr6 , and Rb2TeBr6were determined from differential thermal analysis, microstructural, and microhardness data. The congruently melting composition was found to differ from the stoichiometric composition for Tl2TeBr6and Cs2TeBr6and to coincide with it for Rb2TeBr6 . Single crystals of the compounds studied were prepared using growth charges with the congruently melting compositions, and their properties were investigated.

The compound Rb3Bi2I9 was synthesized by melting a stoichiometric mixture of RbI and BiI3 and annealing for 1 month some degrees below the melting temperature of 785±5K; a large single crystal of the title compound has been grown from the melt by directional solidification using the vertical Bridgman-Stockbarger technique. X-ray structure determination of the compound involved single-crystal diffractometry, direct and Patterson methods and least-squares refinement. Rb3Bi2I9 exhibits a new type of crystal structure, crystallizing in the monoclinic space group Pc with unit-cell parameters a=14.690(4), b=8.195(2), c=25.645(6) A, β=125.39(2)°, V=2517(2) A3, Z=4. The unit-cell of Rb3Bi2I9 has six pseudohexagonal RbI3 layers which are stacked along the direction near to the normal of the XY plane. Each BiI6 octahedron shares three corners with three other octahedra to form parallel Bi2I9 corrugated layers intersecting Z axis of the structure at an angle near 120°.

The compound Rb3Bi2I9 was synthesized by melting a stoichiometric mixture of RbI and BiI3 and annealing for 1 month some degrees below the melting temperature of 785±5K; a large single crystal of the title compound has been grown from the melt by directional solidification using the vertical Bridgman-Stockbarger technique. X-ray structure determination of the compound involved single-crystal diffractometry, direct and Patterson methods and least-squares refinement. Rb3Bi2I9 exhibits a new type of crystal structure, crystallizing in the monoclinic space group Pc with unit-cell parameters a=14.690(4), b=8.195(2), c=25.645(6) A, β=125.39(2)°, V=2517(2) A3, Z=4. The unit-cell of Rb3Bi2I9 has six pseudohexagonal RbI3 layers which are stacked along the direction near to the normal of the XY plane. Each BiI6 octahedron shares three corners with three other octahedra to form parallel Bi2I9 corrugated layers intersecting Z axis of the structure at an angle near 120°.