Enthalpy of formation of rare-earth silicates Y{sub 2}SiO{sub 5} and Yb{sub 2}SiO{sub 5} and N-containing silicate Y{sub 10}(SiO{sub 4}){sub 6}N{sub 2}
- Thermochemistry Facility, Chemistry Building, Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616 (United States)
- Max-Planck-Institut fuer Metallforschung and Universitaet Stuttgart, Institut fuer Nichtmetallische Anorganische Materialien Pulvermetallurgisches Laboratorium, Heisenbergstr 5, D-70569 Stuttgart (Germany)
The enthalpies of formation of two rare-earth silicates (Y{sub 2}SiO{sub 5} and Yb{sub 2}SiO{sub 5}) and a N-containing rare-earth silicate Y{sub 10}(SiO{sub 4}){sub 6}N{sub 2} have been determined using high-temperature drop solution calorimetry. Alkali borate (52 wt{percent} LiBO{sub 2}{center_dot}48 wt{percent} NaBO{sub 2}) solvent was used at 800 {degree}C, and oxygen gas was bubbled through the melt. The nitrogen-containing silicate was oxidized during dissolution. The standard enthalpies of formation are for Y{sub 2}SiO{sub 5}, Yb{sub 2}SiO{sub 5}, and Y{sub 10}(SiO{sub 4}){sub 6}N{sub 2}, respectively, {minus}2868.54{plus_minus}5.34, {minus}2774.75{plus_minus}8.21, and {minus}14145.20{plus_minus}16.48 kJ/mol from elements, and {minus}52.53{plus_minus}4.83, {minus}49.45{plus_minus}8.35, and {minus}94.53{plus_minus}11.66 kJ/mol from oxides (Y{sub 2}O{sub 3} or Yb{sub 2}O{sub 3}, SiO{sub 2}) and nitride (Si{sub 3}N{sub 4}). The silicates and N-containing silicate are energetically stable with respect to binary oxides and Si{sub 3}N{sub 4}, but the N-containing silicate may be metastable with respect to assemblages containing Y{sub 2}SiO{sub 5}, Si{sub 3}N{sub 4}, and SiO{sub 2}. A linear relationship was found between the enthalpy of formation of a series of M{sub 2}SiO{sub 5} silicates from binary oxides and the ionic potential (z/r) of the metal cation. {copyright} {ital 1999 Materials Research Society.}
- OSTI ID:
- 348149
- Journal Information:
- Journal of Materials Research, Vol. 14, Issue 4; Other Information: PBD: Apr 1999
- Country of Publication:
- United States
- Language:
- English
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