Czochralski growth of single-crystal fayalite under controlled oxygen fugacity conditions

Journal Article · Sat Mar 01 00:00:00 EST 1980 · Am. Mineral.; (United States)

OSTI ID:6599597

Finch, C B ^[1]; Clark, G W; Kopp, O C

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1. Oak Ridge National Lab., TN

Single-crystal boules of fayalite (Fe/sub 2/SiO/sub 4/) were grown in the temperature range 1165 to 1200/sup 0/C at 1 bar total pressure from high-purity oxide melts of 1.95:1 to 2.10:1 Fe:Si atom ratio. A modified Czochralski technique was used, with platinum crucibles inductively heated under oxygen fugacities, f(O/sub 2/), between 10/sup -9/ and 10/sup -12/ bar. The boules are up to 10 mm in diameter by 40 mm long and brownish-black in color. The best crystal homogeneity was obtained at growth rates of less than or equal to 3 mm/h from 2.1:1 Fe:Si melts at an f(O/sub 2/) of 10/sup -12/ bar at 1180 to 1185/sup 0/C. Colorimetric data indicate boule Fe/sup 3 +/ contents which increase with synthesis f(O/sub 2/) from 0.27% (10/sup -12/ bar) to 0.86% (10/sup -9/ bar). The typical orthohombic unit-cell parameters are a = 4.8214 to 4.8219, b = 10.4774 to 10.4767, and c = 6.0880 to 6.0893 A, varying slightly with synthesis f(O/sub 2/). The optical and infrared absorption spectrum is similar to that of natural fayalite, exhibiting a broad absorption band at 10,000 A with transparency maxima at 7000 and 25,000 A. Samples appear stable up to melting at approx. 1202/sup 0/C(f(O/sub 2/) approx. = 10/sup -12/ bar), but lose weight and solidify incongruently.

• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 6599597
• Journal Information: Am. Mineral.; (United States), Vol. 65:3-4
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
IRON SILICATES
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CZOCHRALSKI METHOD
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MAGNESIUM SILICATES
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