Density functional study of structures and mechanical properties of Y-doped alpha-SiAlONs

Autor(en)

Lubomir Benco, Juergen Hafner, Zoltan Lences, Pavol Sajgalik

Abstrakt

2 x 2 x 1 supercell of alpha-Si3N4 is used to model Y-doped alpha-SiAlON's(silicoalumino oxonitrides). Ab initio total energy calculations are performed at the DFT (GGA) level. A full relaxation of atomic positions is performed for stoichiometric alpha-SbN4 and for a series of substituted structures with concentrations of Y, Al and O increasing up to the composition Y0.5Si9.5Al2.5O1.0N15.0, similar to the observed solubility limits. The avoidance of neighboring AlX4 (X = N,O) tetrahedra in highly doped structures indicates that the distribution of Al atoms in the framework of (X-SiAlON's obeys the same Loewenstein rule as in aluminosilicate zeolite structures. An increase of the lattice parameters and cell volumes is observed with increasing degree of the doping. Changes are more pronounced for the insertion of Y than for Si-N/Al-O substitution. An introduction of a Y3+, cation into the interstitial position in the cage, however, causes a local contraction of the structure. Via the contraction a more efficient Y-N bonding is formed, leading to the stabilization of the Y-doped structure. The pronounced increase of the cell volume and the lattice parameters with Y-doping is due to three framework AVSi framework substitutions compensating the extraframework Y3+ cation. The calculated bulk modulus (B-0) ranges from 223 GPa for pure alpha-Si3N4 to 197 GPa for Y0.5Si9.5Al2.5O1.0N15.0. The slope of the decrease of B-0 with the degree of doping depends on the Y-content. For constant concentration of Y an increasing content of O causes a linear decrease of B-0.

Organisation(en)

Computergestützte Materialphysik

Externe Organisation(en)

Slovenian Academy of Sciences and Arts

Journal

Journal of the European Ceramic Society / European Ceramic Society. Journal

Band

28

Seiten

995-1002

Anzahl der Seiten

8

ISSN

0955-2219

DOI

https://doi.org/10.1016/j.jeurceramsoc.2007.09.030

Publikationsdatum

2008

Peer-reviewed

Ja

ÖFOS 2012

103015 Kondensierte Materie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/67b11d52-b269-42d3-a649-5dde7d98b928