Abstract
Oxy-apatites have been attracting increasing attention from researchers due to their excellent conductivity at relatively low temperatures and low oxygen partial pressures compared with the requirements of ZrO2 solid electrolytes. In this article we report on the successful low temperature synthesis of the interstitial-oxygen silicate apatites CaxLa10-x(SiO4)6O3-x/2 (x=0, 0.5, 1.0, 1.5 and 2) via a sol-gel method. The apatite phases were characterized by TG-DTA, XRD, IR and SEM. Their conducting properties were studied by electrochemical impedance spectroscopy (EIS). It was found that the conductivity increased with increases in interstitial oxygen concentration, whereas the activation energy decreased. The conductivity of La10(SiO4)6O3 is 7.98×10-3 S·cm-1 at 700°C, which is about 21000 times higher than that of Ca2La8(SiO4)6O2. This suggests that interstitial oxygen may greatly promote oxygen ionic conductivity. The number of oxygen ions transported and the dependence of electrical conductivity on oxygen partial pressure indicate that the charge carriers of the oxyapatite are oxygen ions; the synthesized samples were oxide ion conductors.
Original language | English |
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Pages (from-to) | 579-583 |
Number of pages | 5 |
Journal | Harbin Gongcheng Daxue Xuebao/Journal of Harbin Engineering University |
Volume | 30 |
Issue number | 5 |
DOIs | |
Publication status | Published - May 2009 |
Externally published | Yes |
Keywords
- Electrochemical impedance spectroscopy
- Free oxygen ion conduction
- Interstitial oxygen ionic conduction
- Silicate apatites
- Sol-gel method