Synthesis and Characterization of Hydrated Rubidium Thio-hydroxosilicogermanates Using Mechanochemical Hydrothermal Synthesis
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- 作者：Carly R. Nelson ; Sarah Olson ; Steven A. Poling ; Steve W. Martin
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：December 26, 2006
- 年：2006
- 卷：18
- 期：26
- 页码：6436 - 6441
- 全文大小：196K
- 年卷期：v.18,no.26(December 26, 2006)
- ISSN：1520-5002
文摘
The synthesis, structure, and proton conductivity of the hydrated thio-hydroxosilicogermanatesRbzGexSi1-xSz(OH)4-z·yH2O (2 
z 3; 0 < y < 1.7) are reported. X-ray diffraction indicates that thez = 2 materials are amorphous and show no unreacted starting materials, which is consistent with themechanochemical hydrothermal evaporation-precipitation synthesis method. Infrared spectroscopy showsa fully reacted system where both silicon and germanium central anions have vibrational modes at ~950,~780, ~667, and ~450 cm-1 associated with asymmetric modes for Si-O, Ge-O, Si-S, and Ge-Schemical bonds, respectively. O-H stretching and bending modes are present at ~3370 and 1655 cm-1,respectively, with the intensities of both modes decreasing with the addition of SiO2. Raman spectroscopyreveals symmetric stretching modes of the Ge-S unit at ~420 cm-1. A new peak appears at ~460 cm-1with the substitution of Si4+ for Ge4+. There are weak peaks above ~460 cm-1 that can be attributed toH2O and O-H libration modes. Thermogravimetric analysis shows that water loss begins above thesynthesis temperature of ~75 
C. All water is lost by ~300 C which is consistent with the onset of theloss of conductivity. Alternating current impedance spectroscopy measurements performed on low-pressuresealed pellets show conductivity values ranging from 10-5 to 10-2.5 S/cm from ~100 to 260 C,respectively. Maximum conductivity values of 10-4.5 and 10-3.5 S/cm at 120 C are obtained for 2RbSH+ 0.9GeO2 + 0.1SiO2 + 0.8H2O and 3RbSH + 0.9GeO2 + 0.1SiO2 + 1.1H2O, respectively. a.c.impedance experiments under humidified conditions resulted in large increases in the proton conductivityat low temperatures. For x = 0.9 and 0.8 for the 2RbSH + xGeO2 + (1-x)SiO2 + yH2O samples, thehumidified d.c. conductivity was ~10-4 S/cm at 60 C, up from ~10-8 S/cm for samples measuredunder dry nitrogen. The effects of water and SiO2 content on the proton conductivity are also discussed.
z 3; 0 < y < 1.7) are reported. X-ray diffraction indicates that thez = 2 materials are amorphous and show no unreacted starting materials, which is consistent with themechanochemical hydrothermal evaporation-precipitation synthesis method. Infrared spectroscopy showsa fully reacted system where both silicon and germanium central anions have vibrational modes at ~950,~780, ~667, and ~450 cm-1 associated with asymmetric modes for Si-O, Ge-O, Si-S, and Ge-Schemical bonds, respectively. O-H stretching and bending modes are present at ~3370 and 1655 cm-1,respectively, with the intensities of both modes decreasing with the addition of SiO2. Raman spectroscopyreveals symmetric stretching modes of the Ge-S unit at ~420 cm-1. A new peak appears at ~460 cm-1with the substitution of Si4+ for Ge4+. There are weak peaks above ~460 cm-1 that can be attributed toH2O and O-H libration modes. Thermogravimetric analysis shows that water loss begins above thesynthesis temperature of ~75 C. All water is lost by ~300 C which is consistent with the onset of theloss of conductivity. Alternating current impedance spectroscopy measurements performed on low-pressuresealed pellets show conductivity values ranging from 10-5 to 10-2.5 S/cm from ~100 to 260 C,respectively. Maximum conductivity values of 10-4.5 and 10-3.5 S/cm at 120 C are obtained for 2RbSH+ 0.9GeO2 + 0.1SiO2 + 0.8H2O and 3RbSH + 0.9GeO2 + 0.1SiO2 + 1.1H2O, respectively. a.c.impedance experiments under humidified conditions resulted in large increases in the proton conductivityat low temperatures. For x = 0.9 and 0.8 for the 2RbSH + xGeO2 + (1-x)SiO2 + yH2O samples, thehumidified d.c. conductivity was ~10-4 S/cm at 60 C, up from ~10-8 S/cm for samples measuredunder dry nitrogen. The effects of water and SiO2 content on the proton conductivity are also discussed.