Vibrational Spectroscopic Study of Structural Evolution in the Coprecipitated Precursors to La2Sn2O7 and La2Ti2O7 |
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| Authors: | Junichi Takahashi Toshiaki Ohtsuka |
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| Affiliation: | Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, Japan;Electrochemistry Laboratory, Faculty of Engineering, Hokkaido University, Sapporo 060, Japan |
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| Abstract: | Structural evolution in the X-ray amorphous precursors to La2Sn2O7 and La2Ti2O7 is examined using IR and Raman spectroscopy. These precursors are prepared by rapid coprecipitation from mixed aqueous solutions of the corresponding metal chlorides. Rapid coprecipitation from an SnCl2−6 and La3+-containing aqueous solution yields microcrystalline particles of SnO2· n H2O and La(OH)3, which instantaneously interconnect to form an ultimate, complex colloid particle. The Ti(OH)2+2 and La3+ in the other solution system coprecipitate into a different, complex colloid (an unidentified phase), which is definitely not a mixed dispersion of single-component colloids. A comparative examination of the vibrational spectra of the coprecipitates heated to various temperatures indicates that the SnO2 and anatase phases develop in the respective precursors before crystallization of the desired double oxides. Crystallization itself can be attributed to a solid-state reaction among the various microcrystallites of each single-metal oxide in a gel particle of the precursor. |
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| Keywords: | colloids lanthanum tin titanium coprecipitation |
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