Structural, Thermal and Electrical Studies of Thallium-Scandium-hafnium(zirconium) Molybdates

Thallium scandium hafnium molybdate Tl5ScHf(MoO4)(6) and thallium scandium zirconium molybdate Tl5ScHf(MoO4)(6) crystallize in trigonal symmetry with the space group R (3) over barc. The compounds are synthesized by sintering the finely powdered simple molybdates mixture in a muffle furnace at 723-823 K for 100 h. The crystal structures of Tl5ScHf(MoO4)(6) and Tl5ScHf(MoO4)(6) are obtained by Rietveld method. The following unit cell parameters are calculated for Tl5ScHf(MoO4)(6) : a = 10.62338 (5), c = 38.0579 (2) angstrom, V = 3719.64 (4) angstrom(3), Z = 6 and for Tl5ScHf(MoO4)(6) : a = 10.63216 (7), c = 38.0716 (3) angstrom, V = 3727.14 (5) angstrom(3), Z = 6. The conductivity of the Tl5ScHf(MoO4)(6) and Tl5ScHf(MoO4)(6) are measured between 293 and 860 K. The ionic conductivity of Tl5ScHf(MoO4)(6) and Tl5ScHf(MoO4)(6) molybdates are 8 x 10(-4) S/cm and 8 x 10(-3) S/cm (at 773 K); the activation energy of ionic transfer are 0.8 eV and 0.3 eV respectively.