Abstract
A new disodium dipotassium cobalt aluminate hexaarsenate Na2K2Co5.5Al(AsO4)(6) was synthesized by solid state route at 1193 K. The crystalline structure was determined by X-ray diffraction at room temperature. The new member of 13-Xenophyllite material crystallizes in the monoclinic of the C2/m space group with the unit cell parameters: a=10.738(3) angstrom, beta= 14.793 (2) angstrom, c=6.723(3) angstrom, beta = 105.365 degrees (10), V= 1336.8(4) angstrom(3) and Z=4. The crystal structure validation was carried out using Bond Charge distribution (CHARDI) and Bond Valence Sum (BVS) tools. The anionic framework can be described as tridimentionnal anionic framework sowing large hexagonal tunnels along [100] direction where the sodium and potassium cations are located. The electrical property of the title material was characterized by impedance spectroscopy technique from 553 to 753K temperature range using the frequency response analyzer with 0.05V amplitude signal over the range of 13MHz-5Hz. The conductivity value of the sample at 533K is 2.06x 10 -5 S.cm(-1), the activation energy Ea = 0.536eV, show that the Na2K2Co5.5Al(AsO4)(6) compound is an ionicconductor. The alkali ions conduction pathways in the studied compound were simulated via the bond valence site energy model (BVSE).