ELECTROCHEMICAL FORMATION AND CHARACTERIZATION OF MIXED VALENCE AND ABNORMAL VALENCE OXIDE FILMS

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1. Formation conditions of abnormal valence Cr compound LaCrO_4 from the precursor films electrodeposited from La (III) -Cr (VI) solutions were established. Thermally stable regions of LaCrO_4 were determined as functions of temperature, heating time and oxygen partial pressure. LaCrO_4 is stable below 500ﾟC independent of oxygen partial pressure and does not decompose in a vacuo at room temperature.2. Electric conductivity of LaCrO_4 film increased exponentially with temperature above 150ﾟC,indicating a similar property to semiconductors. The conductivity was higher than that of perovskite type LaCrO_3 film formed by the same process, but the valency control of A site showed no effect on the conductivity.3. Mixed valence molybdenum oxyhydroxide films were formed by cathodic deposition from solutions of ammonium molybdate and magnesium sulfate (MgSO_4). MgSO_4 was found to be a necessary component in the solution to from uniform and adhesive films.4. The mixed valence molybdenum oxyhydroxide films were amorphous and didn't crystallize by heating at 200ﾟC for 12 hours. Spectrophotometric emissivity of the films at 100ﾟC was about 30-50% in the IR region of 4-10 mum and it increased to more than 90% for longer wave length than 10 mum. The films showed electric conductivity with or without drying. These characteristics suggest that the films are potentially useful material for many purposes such as a far IR radiator, sensors, IR detectors, and so on.5. It was found that gel-like oxyhydroxide films of mixed valence rare-earch elements, such as Ce (III) -Ce (IV), can be formed by cathodic polarization in nitrate solutions of rare-earth elements.