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摘要: 高溫質子導體固體電解質Ba3Ca1+xNb2?xO9?δ化學性質穩定,中低溫電導率較高,具有較好的應用前景。采用固相合成法制備得到了復合鈣鈦礦相的Ba3Ca1+xNb2?xO9?δ(x=0、0.10、0.18、0.30)材料。隨著Ca摻雜量的增加Ba3Ca1+xNb2?xO9?δ樣品的電導率先增加后降低,x=0.18的樣品電導率最高。Ba3Ca1+xNb2?xO9?δ材料在含氫中的電子空穴遷移數較低,當溫度低于750 ℃時,材料中質子導電為主;當溫度達800 ℃后,材料中氧離子導電為主。x=0.10的樣品質子遷移數最高,隨著摻雜量的增加樣品氧離子遷移數逐漸增大,質子遷移數逐漸降低。Abstract: ABO3-type perovskite oxides and A3B′B′′2O9-type composite perovskite oxides exhibit proton conduction from 200 ℃ to 1000 ℃. These high-temperature proton conductors have received considerable attention due to their promise as electrolytes in fuel cells, electrolytic hydrogen production, hydrogen separation, electrochemical reactors, sensors, etc. The Ba3Ca1+xNb2?xO9?δ composite perovskite-type solid electrolyte has stable chemical properties and corrosion resistance to CO2 and H2O, so it can be used in long-term electrochemical devices. Protons are incorporated into Ba3Ca1+xNb2?xO9?δ in a humid or hydrogen-containing atmosphere because of the reaction of H2O and oxygen vacancies in proton conductors. However, proton conductors also exhibit oxygen vacancy conduction in the high-temperature range. In addition, electron holes can be generated by an oxygen vacancy reaction with atmospheric oxygen, causing proton conductors to exhibit electron-hole conduction. Hence, more oxygen vacancies can be produced with more Ca2+ dopant in Ba3Ca1+xNb2?xO9?δ due to a lack of positive charge. Meanwhile, the proton and electron-hole concentrations increase with oxygen vacancies, and the conductivity of Ba3Ca1+xNb2?xO9?δ can be improved. However, the crystal structure of Ba3Ca1+xNb2?xO9?δ can be changed with Ca2+ doping, and changes in proton, oxygen vacancy, and electron-hole transport numbers, the ratio of protons, oxygen vacancies, and electron-hole conductivity to total conductivity respectively, are unknown with Ca2+ doping, with different effects of crystal structure for protons, oxygen vacancies, and electron-hole conduction. Ba3Ca1+xNb2?xO9?δ has high conductivity in a humid atmosphere, and the proton transport number with doping amount needs to be further studied. In this work, Ba3Ca1+xNb2?xO9?δ (x=0, 0.10, 0.18, and 0.30) with a composite perovskite phase was prepared using a solid-state reaction method. With the increase in Ca2+ doping amount, the conductivity of Ba3Ca1+xNb2?xO9?δ samples first increased and then decreased, and the conductivity of the sample with x=0.18 was the highest. The electron-hole transport number of Ba3Ca1+xNb2?xO9?δ under the atmosphere containing hydrogen was relatively low. Protons were mainly conductive carriers in Ba3Ca1+xNb2?xO9?δ below 750 ℃, while Ba3Ca1+xNb2?xO9?δ exhibited mainly oxygen vacancy conduction at 800 ℃. With the increase in dopant amount, the oxygen vacancy transport number of Ba3Ca1+xNb2?xO9?δ increased gradually, while the proton transport number decreased gradually.
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Key words:
- proton conductor /
- perovskite /
- conductivity /
- carriers /
- transport number
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參考文獻
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