STRUCTURAL CHARACTERIZATION AND ELECTRICAL-PROPERTIES OF A NOVEL DEFECT PYROCHLORE

Improved structural parameters for the defect pyrochlore K3/2Cr1/2Te3/ 2O . 0.5H(2)O have been determined by employing a full-profile Rietvel d structure analysis of X ray powder-diffraction data. These results m ake it possible to establish the location of the atoms in the Fd3m spa ce group as follows: K (32e), Te/Cr (16d), and O (48f); the unit cell parameter is a = 10.039 (1). The ionic conductivity of this material h as been determined by ac methods (complex impedance measurements) in p ressed pellets and the obtained data suggest the unique contribution o f K mobile cation, with an activation energy of 0.7 eV. (C) 1995 Acade mic Press, Inc.