Effect of germanium oxide (GeO 2) additive on the anatase-to-rutile phase transition

Kiyoshi Okada, Ken Ichi Katsumata, Yoshikazu Kameshima, Atsuo Yasumori

Research output: Contribution to journalArticle

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Abstract

The effect of germanium oxide (GeO 2) addition on the anatase-to-rutile phase transition was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). TiO 2 xerogels containing up to 20 mol% GeO 2 were prepared by refluxing and hydrolyzing titanium tetraisopropoxide (TTIP) and germanium butoxide (GB) using nitric acid as a catalyst. The following occurred with increasing amounts of GeO 2 in the xerogels: (i) the crystallization temperature of anatase increased from 410° to 565°C and the DTA temperature of the anatase-to-rutile phase transition increased from 676° to 977°C in 20 mol% GeO 2-containing xerogel; (ii) the crystaliite size of anatase became smaller; (iii) the lattice a-parameter of the anatase showed little change, but the c-parameter decreased up to 20 mol% GeO 2; (iv) both the lattice a- and c-parameters of the rutile decreased monotonically. From these results, the added GeO 2 is considered to become incorporated into the anatase structure. The following occurred with increasing anatase heating temperature: (i) the lattice c-parameter of the anatase increased gradually and approached the value of pure anatase; and (ii) the chemical composition of the xerogel surfaces, measured by XPS, showed an increase in GeO 2 content, indicating the expulsion of GeO 2 from the anatase to form an amorphous surface layer. The formation of this amorphous GeO 2 surface layer is thought to play an important role in retarding the anatase-to-rutile phase transition by suppressing diffusion between the anatase particles in direct contact, and limiting their ability to act as surface nucleation sites for rutile, as in the case of SiO 2 additions. However, GeO 2 addition is less effective than SiO 2 in retarding the phase transition.

Original languageEnglish
Pages (from-to)2078-2082
Number of pages5
JournalJournal of the American Ceramic Society
Volume85
Issue number8
Publication statusPublished - Aug 2002
Externally publishedYes

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Germanium oxides
Titanium dioxide
Phase transitions
Xerogels
Differential thermal analysis
germanium oxide
titanium dioxide
X ray photoelectron spectroscopy
Nitric acid
Germanium
Temperature

ASJC Scopus subject areas

  • Ceramics and Composites

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Effect of germanium oxide (GeO 2) additive on the anatase-to-rutile phase transition. / Okada, Kiyoshi; Katsumata, Ken Ichi; Kameshima, Yoshikazu; Yasumori, Atsuo.

In: Journal of the American Ceramic Society, Vol. 85, No. 8, 08.2002, p. 2078-2082.

Research output: Contribution to journalArticle

Okada, Kiyoshi ; Katsumata, Ken Ichi ; Kameshima, Yoshikazu ; Yasumori, Atsuo. / Effect of germanium oxide (GeO 2) additive on the anatase-to-rutile phase transition. In: Journal of the American Ceramic Society. 2002 ; Vol. 85, No. 8. pp. 2078-2082.
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abstract = "The effect of germanium oxide (GeO 2) addition on the anatase-to-rutile phase transition was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). TiO 2 xerogels containing up to 20 mol{\%} GeO 2 were prepared by refluxing and hydrolyzing titanium tetraisopropoxide (TTIP) and germanium butoxide (GB) using nitric acid as a catalyst. The following occurred with increasing amounts of GeO 2 in the xerogels: (i) the crystallization temperature of anatase increased from 410° to 565°C and the DTA temperature of the anatase-to-rutile phase transition increased from 676° to 977°C in 20 mol{\%} GeO 2-containing xerogel; (ii) the crystaliite size of anatase became smaller; (iii) the lattice a-parameter of the anatase showed little change, but the c-parameter decreased up to 20 mol{\%} GeO 2; (iv) both the lattice a- and c-parameters of the rutile decreased monotonically. From these results, the added GeO 2 is considered to become incorporated into the anatase structure. The following occurred with increasing anatase heating temperature: (i) the lattice c-parameter of the anatase increased gradually and approached the value of pure anatase; and (ii) the chemical composition of the xerogel surfaces, measured by XPS, showed an increase in GeO 2 content, indicating the expulsion of GeO 2 from the anatase to form an amorphous surface layer. The formation of this amorphous GeO 2 surface layer is thought to play an important role in retarding the anatase-to-rutile phase transition by suppressing diffusion between the anatase particles in direct contact, and limiting their ability to act as surface nucleation sites for rutile, as in the case of SiO 2 additions. However, GeO 2 addition is less effective than SiO 2 in retarding the phase transition.",
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