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Thermal expansion of Si3N4 and Ge3N4
|Roman Minikayev 1, Wojciech Paszkowicz 1, Paweł Piszora 2, Michael Knapp 3, Carsten Baehtz 3|
1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
Si3N4 and Ge3N4 belong to a family of nonoxide ceramics. They exhibit unique physico-chemical and mechanical properties making them suitable for various applications. Si3N4 exhibits superior thermomechanical and physicochemical properties such as oxidation and thermal shock resistance, mechanical fatigue, creep and wear resistance, high fracture toughness, it is chemically inert and hydrophobic. Ge3N4 is known to be thermally stable and resistant to oxidation, its photocatalytic behavior has been reported. Their applications include the use for surface protection  (both compounds), in engine components and turbochargers, bearings, metal cutting and shaping tools and hot metal handling , interlayer dielectrics for metal-insulator–semiconductors devices, metal-nitride-oxide–semiconductors and as passivation films or diffusion masks  (Si3N4), in photodiodes, amplifiers , metal-insulator-semiconductor field effect transistors (MIS FET) , waveguides  Li-ion batteries , and as photocatalysts  (Ge3N4).
In the present study, thermal expansion of Si3N4 and Ge3N4 polymorphs is experimentally determined and discussed on the basis of literature data. Two Si3N4 samples and one Ge3N4 sample (ALDRICH) were studied.
The study was performed under low- and high-temperature conditions by X–ray diffraction, at a synchrotron–radiation source. The diffraction studies were carried out at a powder diffractometer  at the B2 (Hasylab/DESY) bending–magnet beamline, using the Debye–Scherrer geometry. An imaging-plate detector was applied for the data collection. The Rietveld-refinement program Fullprof 2.k (v 2.7)  was used for the structural analysis. The quantitative analysis yielded the following proportions of α and β polymorphs in the samples: 92:8, 9:91 (samples of Si3N4 ) and 27:73 (sample of Ge3N4). The temperature variation of lattice parameters, atomic positions and thermal expansion of α and β nitride show smooth trends. It is concluded that despite the fact that each samples was built from two phases, a combination of applied experimental conditions with the careful analysis using the Rietveld method leads to acceptable values of thermal expansion in the broad temperature range studied.
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Presentation: Poster at IX Krajowe Sympozjum Użytkowników Promieniowania Synchrotronowego, by Wojciech Paszkowicz
See On-line Journal of IX Krajowe Sympozjum Użytkowników Promieniowania Synchrotronowego
Submitted: 2011-06-20 17:15 Revised: 2011-06-20 17:15