排序方式: 共有3条查询结果,搜索用时 0 毫秒
1
1.
The dc conductivity of a sintered sample of Y2 O3 containing an excess of lower-valent metal (Ml) impurities has been measured at 600° to 1100°C in air as a function of the water vapor pressure (0.4 to 3000 Pa). The logarithm of the p -type conductivity vs log P H2o has a slope of – 1/2 in certain regions of F H2o and temperature. This reflects a defect situation where interstitial protons from water vapor balance the excess of lower-valent cation impurities: [H˙ ] = [M1' ]. The activation energy for the p -type conductivity under these conditions is evaluated and interpreted in terms of the enthalpy needed to dissolve interstitial protons in yttria. 相似文献
2.
The electrical conductivity of several sintered yttria ceramics with different levels of lower valent cation impurities was studied as a function of the partial pressure of water vapor (3 to 1600 Pa) at 500° to 1300°C in oxygen or air. At the higher temperatures yttria is a P -type conductor, but at the lowest temperatures and highest water vapor pressures, an ionic contribution becomes significant. The p -type conductivity decreases with increasing water vapor pressure. This is interpreted in terms of a model involving dissolution of hydrogen as interstitial protons and which counterbalance the effective charges of the lower valent impurities. At the higher water vapor pressures and lower impurity levels excess protons are probably compensated by interstitial hydroxide or oxygen ions. Indications of grain boundary segregation of impurities are reported. 相似文献
3.
The electrical conductivity of polycrystalline Y2 O3 has been studied as a function of the partial pressure of oxygen (10–14 to 105 Pa) at 900° to 1500°C in atmospheres saturated with water vapor at 12°C or dried with P2 O5 . Yttria is a p -conductor at high oxygen activities. The p -conductivity increases with increasing P O2 and decreases with increasing PH2O . At low oxygen activities the oxide is a mixed ionic/electronic conductor. The ionic conductivity is approximately independent of P O2 and increases with increasing P H2O . In the Y2 O3 samples, excesses of lower-valent cation impurities (in the 10 to 100 mol-ppm range) are the dominating negatively charged defects, and in the presence of water vapor they are compensated by interstitial protons. At high P H2O levels additional protons are probably compensated by interstitial oxygen ions. At high temperatures (±1100°C) and for high P O2 and low P H2O , the protons are no longer dominant, and the lower-valent cations are mainly compensated by electron holes. The electrical conductivity exhibits hysteresis-like effects which are interpreted in terms of segregation/desegregation of impurities at grain boundaries. The mobility of electron holes in yttria at 1500°C is estimated to be of the order of magnitude of 0.05 cm2 . s–1 . V–1 相似文献
1