Ba2Cu2Te2P2O13: A new telluro-phosphate with S=1/2 Heisenberg chain

Antiferromagnetic Order and Spin-Canting Transition in the Corrugated Square Net Compound Cu3(TeO4)(SO4)·H2O

Strongly correlated electrons in layered perovskite structures have been the birthplace of high-temperature superconductivity, spin liquids, and quantum criticality. Specifically, the cuprate materials with layered structures made of corner-sharing square-planar CuO4 units have been intensely studied due to their Mott insulating ground state, which leads to high-temperature superconductivity upon doping. Identifying new compounds with similar lattice and electronic structures has become a challenge in solid-state chemistry. Here, we report the hydrothermal crystal growth of a new copper tellurite sulfate, Cu3(TeO4)(SO4)·H2O, a promising alternative to layered perovskites. The orthorhombic phase (space group Pnma) is made of corrugated layers of corner-sharing CuO4 square-planar units that are edge-shared with TeO4 units. The layers are linked by slabs of corner-sharing CuO4 and SO4. Using both the bond valence sum analysis and magnetization data, we find purely Cu2+ ions within the layers but a mixed valence of Cu2+/Cu+ between the layers. Cu3(TeO4)(SO4)·H2O undergoes an antiferromagnetic transition at TN = 67 K marked by a peak in the magnetic susceptibility. Upon further cooling, a spin-canting transition occurs at T* = 12 K, evidenced by a kink in the heat capacity. The spin-canting transition is explained on the basis of a J1-J2 model of magnetic interactions, which is consistent with the slightly different in-plane superexchange paths. We present Cu3(TeO4)(SO4)·H2O as a promising platform for the future doping and strain experiments that could tune the Mott insulating ground state into superconducting or spin liquid states.

Structural variety in zinc telluro-phosphates: syntheses, crystal structures and characterizations of Sr2Zn3Te2P2O14, Pb2Zn3Te2P2O14 and Ba2Zn2TeP2O11

Three new zinc telluro-phosphates, Sr2Zn3Te2P2O14 (1), Pb2Zn3Te2P2O14 (2) and Ba2Zn2TeP2O11 (3), were grown by flux method, and their crystal structures were solved by X-ray diffraction method. Although all three crystals crystallize into the same space group P21/c with similar chemical compositions, they exhibit different topology structure types. 1 features a two-dimensional layered structure with the connection of TeO4 and (Zn3TeP2O18)(16-) 12-membered rings (MRs), which are composed of planar square and tetrahedral configuration ZnO4 groups, tetrahedral PO4 and seesaw TeO4. Due to lone-pair Coulomb repulsion of Pb(2+), the structure of 2, which is also composed of unbalanced seesaw TeO4 and ZnO4 groups and distorted PO4 tetrahedra, is slightly different from that of its analog 1. Compound 3 exhibits a complicated three-dimensional network with (Zn2PO9)(9-) 6-MRs and (Zn2Te2O10)(8-) 8-MRs built from distorted tetrahedral ZnO4 and PO4 groups and trigonal pyramidal TeO3 units. According to UV-vis-NIR diffuse reflectance spectra, compounds 1, 2 and 3 are highly transparent in the range of 450 to 2500 nm with a UV cut-off of 275 nm, 330 nm and 278 nm, respectively. In addition, the characterizations, including thermal analyses, XPS measurement and dipole moment calculations, are also reported.