Na7Y2(P2O7)2 (P3O10) – A New Layer and Tunnel Structure

A new layered phosphate, Na₇Y₂(P₂O₇) ₂(P₃O₁₀), containing both [P₂O₇]^4? and [P₃O₁₀]^5? groups, has been prepared. It crystallizes in the monoclinic space group P2/c with a = 16.205(4), b = 5.3746(9), c = 12.309(4) Å, β = 97.96(2)°, V = 1061.7(5) ų and Z = 2. The structure was solved and refined to R₁ = 0.0298 and wR₂ = 0.0698 for 1844 independent reflections with I > 2σ(I). It consists of layers of corner and edge-sharing YO₇ polyhedra, P₂O₇ and P₃O₁₀ groups. Each layer is built up from two parallel [YP₂O₇] slabs, held together by the P₃O₁₀ groups. This arrangement gives rise to intersecting tunnels within the layer. The Na⁺ cations are located in the tunnels and between the layers. Both P₂O₇ and P₃O₁₀ groups contain unshared oxygen atoms directed toward the interlayer space and toward the tunnels. The P₂O₇ groups show a staggered configuration. In addition to this original layered framework, the title compound provides the third example of a compound containing a mixed anion of [P₂O₇]^4? and [P₃O₁₀]^5?. The structure was compared with the two previously reported ones, containing such a mixed anion: NH₄Cd₆(P₂O₇) ₂(P₃O₁₀) [6] and Cs₂Mo₅O₂(P₂O₇)₃ · (P₃O₁₀) [7].     

Groups whose proper subgroups are Baer-by-Chernikov or Baer-by-(finite rank)

Our main result is that a locally graded group whose proper subgroups are Baer-by-Chernikov is itself Baer-by-Chernikov. We prove also that a locally (soluble-by-finite) group whose proper subgroups are Baer-by-(finite rank) is itself Baer-by-(finite rank) if either it is locally of finite rank but not locally finite or it has no infinite simple images.     

Synthesis and crystal structure of K3Sb4BO13

K₃Sb₄BO₁₃, Mr = 823.11 g.mol^–1, crystallizes in the triclinic system, space group P , Z = 2. The lattice parameters are a = 7.133(1) Å, b = 7.232(1) Å, c = 13.259(2) Å, = 82.00 (1)°, = 99.77(1)° and = 117.08(1)°, V = 598.7(2) ų, D_x = 4.566 Mg m^–3. The final R index and weighted R_w index are 0.0251 and 0.0623, respectively. The three-dimensional network of the title compound is constituted by layers (Sb₃O₉)_n, similar to that of hexagonal bronze of Magneli. These layers are linked together, in the c direction, alternatively by edge-sharing pairs of SbO₆ octahedra and BO₃ triangles. This framework has interconnected tunnels, running approximately along the a and b directions, in which the K⁺ ions are located.     

Growth and spectroscopic properties of Yb-doped Li6Y(BO3)3 single crystal

The spectroscopic properties of high-quality Czochralski grown 20% Yb³⁺-doped Li₆Y(BO₃)₃ single crystal as new promising laser material are presented. The crystal was seeded-grown in the 〈0 1 0〉 direction and its crystallinity was measured using X-ray rocking curve analysis. Low temperature transmission spectrum exhibits broad bands in a short range of wavelengths and two sharp lines at 972.5 and 978 nm, interpreted as two zero-lines of two nonequivalent Yb³⁺ centers inside the lattice. The fluorescence lifetimes associated to these two intense lines are different: 0.867 and 1.33 ms. An attempt of determination of the Stark sublevels energies of the ⁴F_5/2 and ⁴F_7/2 manifolds of the two Yb³⁺ nonequivalent ions is given. The polarized absorption and emission spectra were also recorded at room temperature and we conclude that the most favorable emission line for laser application could be around 1042 nm in n_g polarization.