Neutron structural and vibrational studies of dipotassium selenate tellurate

摘要

At room temperature the potassium selenate tellurate K_2SeO_4 centre dot Te(OH)_6 (KSeTe) was prepared from water solution of H_6TeO_6 and K_2SeO_4. Its structure has been determined from single crystal using neutron diffraction data. KSeTe is monoclinic with die space group. The unit cell parameters are: a = 11.572(9) A, b = 6.437(7)A, c= 13.938(1) A, beta= 106.07(1) deg , V=997.7(1)A~3 and Z=4. The main feature of this structure is the presence of two different and independent anions (TeO_6~(6-) and SeO_4~(2-)) in the same unit cell. The structure is built by layers of TeO_4, octahedra altering with planes of SeO_4 tetrahedra linked by a network of hydrogen bonds performed by protons belonging to the OH hydroxide groups. DSC measurements indicate that the crystals of K_2SeO_4 centre dot Te(OH)_6 undergo three endothermal peaks at 433, 480 and 495 K. Raman scattering measurements on KSeTe material taken between 300 and 620 K are reported in this paper. The spectra indicate clearly these phase transitions.