Interfacial electronic structure and full spectral Hamaker constants of Si{sub 3}N{sub 4} intergranular films from VUV and SR-VEEL spectroscopy
- DuPont Co. Central Research, Wilmington, DE (United States)
- Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany). Institut fuer Werkstoffwissenschaft
- Lawrence Berkeley Lab., CA (United States)
The interfacial electronic structure, presented as the interband transition strength J{sub cv}({omega}) of the interatomic bonds, can be determined by Kramers Kronig (KK) analysis of vacuum ultraviolet (VUV) reflectance or spatially resolved valence electron energy loss (SR-VEEL) spectra. For the wetted interfaces in Si{sub 3}N{sub 4}, equilibrium thin glass films are formed whose thickness is determined by a force balance between attractive and repulsive force terms KK analysis of J{sub cv}({omega}) to yield {var_epsilon}{sub 2}({xi}) for the phases present, permits the direct calculation of the configuration-dependent Hamaker constants for the attractive vdW forces from the interfacial electronic structure. Interband transition strengths and full spectral Hamaker constants for Si{sub 3}N{sub 4}samples containing a SiYAlON glass have been determined using SR-VEELS from grains and grain boundaries and compared with results from bulk VUV spectroscopy on separate samples of glass and nitride. The A{sub 121}Hamaker constant for Si{sub 3}N{sub 4} with glass of the bulk composition is 8 zJ (zJ = 10{sup {minus}21}J) from the more established optical method. The EELS method permits the determination of vdW forces based upon actual local compositions and structure, which may differ noticeably from bulk standards. Current results show that full spectral Hamaker constants determined from VUV and SR-VEEL measurements of uniform bulk samples agree, but care must be take in the single scattering and zero loss subtraction corrections, and more work is ongoing in this area. Still the results show that for the grain boundary films present in these polycrystalline Si{sub 3}N{sub 4} samples the glass composition is of lower index of refraction. This can arise from increased oxygen content in determined in situ from the SR-VEELS of a particular grain boundary film. 45 refs.
- OSTI ID:
- 94062
- Report Number(s):
- CONF-941144-; ISBN 1-55899-258-8; TRN: 95:018723
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 28 Nov - 9 Dec 1994; Other Information: PBD: 1995; Related Information: Is Part Of Structure and properties of interfaces in ceramics; Bonnell, D. [ed.] [Univ. of Pennsylvania, PA (United States)]; Ruehle, M. [ed.] [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)]; Chowdhry, U. [ed.] [E.I. duPont de Nemours and Co., Inc., Wilmington, DE (United States)]; PB: 481 p.; Materials Research Society symposium proceedings, Volume 357
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COMPOSITE MATERIALS
INTERFACES
SILICON NITRIDES
ELECTRONIC STRUCTURE
ALUMINIUM OXIDES
YTTRIUM OXIDES
GLASS
SAMPLE PREPARATION
GRAIN BOUNDARIES
ULTRAVIOLET SPECTRA
ENERGY-LOSS SPECTROSCOPY
OPTICAL REFLECTION
ELLIPSOMETRY
REFRACTIVE INDEX
VAN DER WAALS FORCES
EXPERIMENTAL DATA
PHASE STUDIES