Optical and electrochemical properties of Li+ intercalated Zr-Ce oxide and Hf-Ce oxide films

Sputter deposited Zr-Ce oxide and Hf-Ce oxide films were investigated with regard to structure, optical absorption, and electrochemical properties. X-ray diffractometry and Rutherford backscattering spectrometry showed that polycrystalline Zr-Ce oxide and Hf-Ce oxide films had cubic crystal structures for 40-100 mol% CeO2 and 50-100 mol % CeO2, respectively. Cyclic voltammetry was performed in an electrolyte of propylene carbonate containing LiClO4. The charge capacity was similar to 60 mC/cm(2) mu m for a Zr-Ce oxide film with a Ce/Zr atom ratio of similar to 13 as well as for a Hf-Ce oxide film with a Ce/Hf atom ratio of similar to 2. A decrease of the charge capacity was noted after similar to 1000 voltammetric cycles, with the mixed oxide films being far more stable than CeO2. In situ Optical transmittance measurements showed that both Zr-Ce and Kf-Ce oxide films remained essentially transparent during Li+ intercalation. Chronopotentiometry measurements were used to elucidate effects of the electronic structure during Li+ intercalation. (C) 1998 American Institute of Physics. [S0021-8979(98)08303-0].