Metathetic room temperature preparation and characterization of scheelite-type ABO4 (A = Ca, Sr, Ba, Pb;: B=Mo, W) powders

Scheelite-type ABO(4) (A = Ca, Sr, Ba, Pb; B = Mo, W) powders of the shape of small spheres (except BaBO4: needles) were prepared at room temperature by metathetic reactions using aqueous solutions of alkaline or lead chloride, and sodium molybdates or tungstates. The reaction is completed within a minute. The particle size as determined by SEM is of the order of several micrometers. Impedance measurements show activation energies of 0.40 and 0.62 eV for SrWO4 and PbWO4, respectively. EMF measurements indicate ionic transport with an average transference number of 0.86-0.95 over the oxygen partial pressure range 10(-4) to 10(-19) atm in the temperature range 600-850degreesC. (C) 2003 Elsevier B.V. All rights reserved.