Voltammetric measurements on Me O ( Me 5 Bi , Cu , V ) x y compounds and comparison with results for BICUVOX . 10

Voltammetric measurements on cells of arrangement Pt,ArusampleuYSZuAr,Pt with a very small sample mass (‘microsamples’) turned out to be a very convenient tool for the determination of thermodynamic properties of oxides. Measurements were made on Bi O , CuO and V O microsamples and on nickel and copper metal between 550 and 7008C. The 2 3 2 5 measurements on nickel were used for the calibration of the reference electrode. The measurements on CuO showed the advantage of the use of microsamples. Comparison of the results for CuO with the standard potential, calculated from thermodynamic data in the literature, revealed the high accuracy of the method. In the case of measurements on V O a 2 5 possible reaction path was identified. The vanadium system is very complicated because of the large number of stable oxidation states for vanadium in V O compounds. The measurements on Bi O showed a large deviation of about 100–150 x y 2 3 mV from the calculated equilibrium potentials. BICUVOX.10 microsamples are reduced irreversibly below 2 570 mV against a reversible oxygen electrode in 1 atm O at 6008C in the first negative sweep. The voltammograms for 2 BICUVOX.10 are compared with measurements on pure Me O compounds and with calculated data.  1999 Elsevier x y Science B.V. All rights reserved.