High-pressure behavior of. cap alpha. -quartz, oxynitride, and nitride structures

Journal Article · Thu Jan 01 04:00:00 EST 1981 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.328484· OSTI ID:6876741

Cartz, L; Jorgensen, J

The high-pressure behavior of ..cap alpha..-quartz SiO/sub 2/ and GeO/sub 2/, oxynitrides Si/sub 2/N/sub 2/O and Ge/sub 2/N/sub 2/O and ..cap alpha..- and ..beta..-Si/sub 3/N/sub 4/ depends markedly on the nature of the linking of the coordination polyhedra in their crystal structures. Where bond angles can vary between neighboring polyhedra linked at one corner, relative tilting or rotations can occur modifying the aspect of the three-dimensional framework. Such fine structural rearrangements can dominate the reponse of the crystal structure to applied stresses as induced by the application of high pressures or by temperature changes. Direct evidence for this is available from structural measurements at high pressure using time-of-flight neutron diffraction with multicomponent profile refinement procedures, where atomic position changes have been determined up to pressures of approx.3 x 10/sup 9/ Pa. The crystal structures studied are the flexible ..cap alpha..-quartz structures of SiO/sub 2/ and GeO/sub 2/, the partially flexible structures Si/sub 2/N/sub 2/O and Ge/sub 2/N/sub 2/O, and the rigid structures ..cap alpha..- and ..beta..-Si/sub 3/N/sub 4/. The volume compressibility coefficients K/sub v/ are greatest for ..cap alpha..-quartz SiO/sub 2/ (274 x 10/sup -13/ Pa/sup -1/ ) and GeO/sub 2/ (256 x 10/sup -13/ Pa/sup -1/) with the Si-O-Si and Ge-O-Ge angles varying the most; K/sub v/ is intermediate for Si/sub 2/N/sub 2/O (79 x 10-13 Pa/sup -1/ ) and Ge/sub 2/N/sub 2/O (99 x 10/sup -13/ Pa/sup -1/ ) where the Si-O-Si and Ge-O-Ge angles vary appreciably while the bond angles to the nitrogens change only slightly; K/sub v/ is least for ..cap alpha..-Si/sub 3/N/sub 4/ (35.5 x 10/sup -13/ Pa/sup -1/ ) and ..beta..-Si/sub 3/N/sub 4/ (27.5 x 10/sup -13/ Pa/sup -1/ ) where no bond angles vary appreciably. For all of the structures examined, bond length changes with pressure are very small in comparison to bond angle changes, which can be an order of magnitude greater. Each structural type behaves in a characteristic way. For example, Si/sub 2/N/sub 2/O and Ge/sub 2/N/sub 2/O exhibit almost identical responses to pressure.

• Research Organization: College of Engineering, Marquette University, 1515 W. Wisconsin Avenue, Milwaukee, Wisconsin 53233
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6876741
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 52:1; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
BOND ANGLE
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DATA
DIFFRACTION
GERMANIUM COMPOUNDS
GERMANIUM OXIDES
INFORMATION
MOTION
NEUTRON DIFFRACTION
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
QUARTZ
ROTATION
SCATTERING
SILICON COMPOUNDS
SILICON OXIDES
STRESSES
TEMPERATURE DEPENDENCE
THEORETICAL DATA
TIME-OF-FLIGHT METHOD
VERY HIGH PRESSURE