Electrochemical behavior of single crystals of nonstoichiometric cerium(III) fluorides

• Published in: Russian journal of electrochemistry 2009-04, Vol.45 (4), p.393-398
• Main Authors: Urchukova, M. M., Turaeva, M. S.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Electrochemistry; Physical Chemistry
• ISSN: 1023-1935; 1608-3342
• DOI: 10.1134/S1023193509040065

The electrochemical properties of single crystals of cerium fluoride alloyed with bivalent cations Sr 2+ , Ca 2+ , Ba 2+ , Sr 2+ + Ca 2+ , Sr 2+ + Ba 2+ , Ba 2+ + Ca 2+ and also with La 3+ and La 3+ + Ba 2+ cations are studied using the dynamic voltammetry and impedance spectroscopy. The conductivity of symmetrical cells with Ag electrodes is determined using the method of impedance spectroscopy in the frequency range from 450 to 5 kHz at the temperatures from 20 to 100°C: for CeF 3 : Sr 2+ (0.5 mol %) + Ba 2+ (0.5 mol %), σ = σ 0 exp[(−0.284 ± 0.005/ kT ]; for CeF 3 :Ca 2+ (0.5 mol %) + Sr 2+ (0.5 mol %), σ = σ 0 exp[(−0.292 ± 0.017/ kT ]. The steady-state and dynamic voltammogams of symmetrical electrochemical cells with nonpolarizable reference electrodes and CeF 3 single crystals alloyed with Sr 2+ , Ca 2+ , and Ba 2+ bivalent cations exhibited ohmic polarization. For cells with CeF 3 containing La 3+ as an admixture, a hysteresis was observed, which could not be eliminated by chemical and electrochemical treatment of crystals. In the dynamic voltammetric curves of asymmetric cells with nonpolarizable and silver electrode and CeF 3 crystals alloyed with Sr 2+ , Ca 2+ , and Ba 2+ , a range of ideal polarizability (from 0 to ∼−2.7 V), and also cerium redox processes and silver fluorination-boundary regeneration were observed. In the dynamic voltammetric curves of asymmetric cells with CeF 3 containing La 3+ admixture, no range of ideal polarizability was observed; however, the reactions of silver fluorination and reduction of solid-electrolyte cerium were well pronounced at the corresponding potentials.