Solid Solubility and Transport Properties of Nanocrystalline(CeO2)1-x(BiO1.5)x by Hydrothermal Con
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- 作者：Guangshe Li ; Yachun Mao ; Liping Li ; Shouhua Feng ; Minqiang Wang ; and Xi Yao
- 刊名：Chemistry of Materials
- 出版年：1999
- 出版时间：May 1999
- 年：1999
- 卷：11
- 期：5
- 页码：1259 - 1266
- 全文大小：124K
- 年卷期：v.11,no.5(May 1999)
- ISSN：1520-5002
文摘
A series of nanocrystalline solid solutions (CeO2)1-x(BiO1.5)x (x = 0.0-0.5) were synthesizedby mild hydrothermal conditions at 240 
C. The products were characterized by X-raydiffraction (XRD), scanning electronic microscope (SEM), X-ray photoelectron spectroscopy(XPS), and electron paramagnetic resonance (EPR). Different from the solid-state reactionsystems, the solution limit of Bi2O3 in ceria by hydrothermal conditions was as high as ca.50%. XRD data showed that all solid solutions crystallized in single-phase cubic fluorite-type structure. The average grain size of all solid solutions was within nanometer scale.XPS data gave evidence of the presence of Bi(III) and Ce(IV) on the surface of the dopedceria. EPR measurements confirmed Ce(III) ions in the bulk of the sintered solutions. Whenthe content of dopant Bi2O3 in ceria was lower than the limit, air firing of the as-made dopedceria up to 800 C did not lead to any structural transformation. For the solution (CeO2)0.5(BiO1.5)0.5, however, sintering it in air at 800 C would destabilize the cubic fluorite structureand result in segregation of an unknown phase. The ionic conduction measured by impedancespectroscopy showed that the solid solutions with dopant content lower than the limitexhibited primarily the bulk conduction, whereas for the sintered (CeO2)0.5(BiO1.5)0.5, boththe bulk and grain boundary resistance decreased dramatically with increasing temperaturewhen using silver electrode. The solution (CeO2)0.6(BiO1.5)0.4 was determined to be the bestconducting phase. For the nanocrystalline solutions (CeO2)1-x(BiO1.5)x, the bulk conductionwas due to oxide ions. The variations of the activation energy and conductivity with dopantcontent were interpreted in terms of the relative content of the dopant-defect complexes,CeCe'Vö/BiCe'Vö@mx@.
C. The products were characterized by X-raydiffraction (XRD), scanning electronic microscope (SEM), X-ray photoelectron spectroscopy(XPS), and electron paramagnetic resonance (EPR). Different from the solid-state reactionsystems, the solution limit of Bi2O3 in ceria by hydrothermal conditions was as high as ca.50%. XRD data showed that all solid solutions crystallized in single-phase cubic fluorite-type structure. The average grain size of all solid solutions was within nanometer scale.XPS data gave evidence of the presence of Bi(III) and Ce(IV) on the surface of the dopedceria. EPR measurements confirmed Ce(III) ions in the bulk of the sintered solutions. Whenthe content of dopant Bi2O3 in ceria was lower than the limit, air firing of the as-made dopedceria up to 800 C did not lead to any structural transformation. For the solution (CeO2)0.5(BiO1.5)0.5, however, sintering it in air at 800 C would destabilize the cubic fluorite structureand result in segregation of an unknown phase. The ionic conduction measured by impedancespectroscopy showed that the solid solutions with dopant content lower than the limitexhibited primarily the bulk conduction, whereas for the sintered (CeO2)0.5(BiO1.5)0.5, boththe bulk and grain boundary resistance decreased dramatically with increasing temperaturewhen using silver electrode. The solution (CeO2)0.6(BiO1.5)0.4 was determined to be the bestconducting phase. For the nanocrystalline solutions (CeO2)1-x(BiO1.5)x, the bulk conductionwas due to oxide ions. The variations of the activation energy and conductivity with dopantcontent were interpreted in terms of the relative content of the dopant-defect complexes,CeCe'Vö/BiCe'Vö@mx@.