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

1.建立了从La(III)-Cr(VI)溶液中电沉积的前驱体薄膜生成反常价铬化合物LaCrO_4的条件。确定了LaCrO_4的热稳定区为温度、加热时间和氧分压的函数。LaCrO_4在500ﾟC以下是稳定的，与氧分压无关，在室温下不会在真空中分解。LaCrO_4薄膜的电导率随温度的升高而呈指数增加，表明LaCrO_4薄膜的电导率与半导体相似。薄膜的电导率高于相同工艺制备的钙钛矿型LaCrO_3薄膜，但A位的价态控制对薄膜的电导率没有影响。以钼酸铵和硫酸镁溶液为原料，采用阴极沉积法制备了混合价钼氧氢氧化物薄膜。发现硫酸镁是形成均匀和粘合薄膜的溶液中必不可少的成分。混合价钼氧氢氧化物薄膜为非晶态，在200ﾟC加热12h不晶化。在100ﾟC下，薄膜的光谱发射率在4-10微米的红外区约为30-50%，当波长大于10微米时，发射率可达90%以上。薄膜在干燥或不干燥的情况下均表现出导电性。这些特性表明，该薄膜在远红外辐射器、传感器、红外探测器等方面具有潜在的应用价值。研究发现，在稀土元素硝酸盐溶液中，通过阴极极化可以形成Ce(III)-Ce(IV)等混价稀土元素的胶状氢氧化物薄膜。

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.