Termička stabilnost silicij–ugljik amorfnih legura nanesenih magnetronskim izvorima

Amorphous a-Si0.85C0.15:H and a-Si0.6C0.4:H alloys were deposited onto a non-heated substrate using a magnetron source. The samples were exposed to a sequential iso-chronal thermal annealing up to 1000 ° C in a vacuum chamber, and were investigated by the IR spectroscopy and X-ray diffraction measurements. The influence of the thermal treatment on structural ordering was monitored by the evolution of the intensity and shape of the spectral IR lines corresponding to the Si-H and Si-C bonds. At low temperatures, the most pronounced features were accompanied with hydrogen evolution which completes up to 400 ° C. Up to 800 ° C the Si-C absorption lines have gradually changed their shape, peak position and intensity. At 900 ° C, the abrupt changes occured, denoting final transition to crystalline state.Slojevi amorfnog a−Si0.85C0.15:H i a−Si0.6C0.4:H su formirani magnetronskim izvorom, na nezagrijanoj podlozi. Nakon depozicije, uzorci su postepeno grijani u vakuumu do 1000 ◦C. Između uzastopnih grijanja vršena su mjerenja infra–crvenom spektroskopijom i difrakcijom X-zraka. Utjecaj ovakvog termalnog tretmana na strukturno uređenje uzoraka je praćeno razvojem intenziteta i oblika spektralnih linija koje odgovaraju Si−H i Si−C vezama. Na nižim temperaturama, najizrazitije promjene su vezane za desorpciju vodika, koja završava do 400 ◦C. Daljnjim grijanjem do 800 ◦C, linije postepeno mijenjaju oblik, intenzitet i frekvenciju maksimuma. Grijanje na i iznad 900 ◦C uzrokuje nagle promjene, označavajući prijelaz u kristalinično stanje

Profil sinhrontronske rengenske difrakcijske linije

We analyse diffraction line profiles obtained at the X3B1 National Synchrotron Light Source powder-diffraction beamline. Calculated diffraction-line widths are compared to the measurements of a National Institute of Science and Technology Standard Reference Material, LaB6. The discrepancy at high Bragg angles is probably caused by the inadequate Gaussian approximation for the Darwin width of monochromator Bragg reflection. The equatorial-slit width has a major influence not only on vertical (equatorial) divergence but also on the character of diffraction-line profiles at high angles. The least-squares fits of instrument-function deconvoluted tungsten-line profiles show that a Voigt function satisfactorily models physically broadened line profiles.Analizirali smo difrakcijske profile linija dobivenih na snopu X3B1 Nacionalnog sinhrotronskog izvora svjetlosti u Brookhavenu. Načinili smo usporedbe za razne uvjete i s više prilagodbenih funkcija. Prilagodbe primjenom najmanjih kvadrata za profile volframovih linija, koje su bile dekonvoluirane instrumentalnom funkcijom, pokazuju da Voigtova funkcija dobro opisuje fizičko proširenje profila linija

Profil sinhrontronske rengenske difrakcijske linije

We analyse diffraction line profiles obtained at the X3B1 National Synchrotron Light Source powder-diffraction beamline. Calculated diffraction-line widths are compared to the measurements of a National Institute of Science and Technology Standard Reference Material, LaB6. The discrepancy at high Bragg angles is probably caused by the inadequate Gaussian approximation for the Darwin width of monochromator Bragg reflection. The equatorial-slit width has a major influence not only on vertical (equatorial) divergence but also on the character of diffraction-line profiles at high angles. The least-squares fits of instrument-function deconvoluted tungsten-line profiles show that a Voigt function satisfactorily models physically broadened line profiles.Analizirali smo difrakcijske profile linija dobivenih na snopu X3B1 Nacionalnog sinhrotronskog izvora svjetlosti u Brookhavenu. Načinili smo usporedbe za razne uvjete i s više prilagodbenih funkcija. Prilagodbe primjenom najmanjih kvadrata za profile volframovih linija, koje su bile dekonvoluirane instrumentalnom funkcijom, pokazuju da Voigtova funkcija dobro opisuje fizičko proširenje profila linija

IMPROVED MODELING OF RESIDUAL STRAIN/STRESS AND CRYSTALLITE-SIZE DISTRIBUTION IN RIETVELD REFINEMENT

ABSTRACT We propose two improvements to the microstructural modeling in Rietveld refinement. The first is the model that yields the complete texture-weighted strain and stress tensors as a function of crystallite orientations, as well as the average values of macroscopic strain and stress tensors for all Laue classes. Implementation in the Rietveld refinement program can be made through the set of refinable parameters that allow the calculation of strain and stress values. Another topic discussed is the problem of determination of coherently diffracting domain size and domain-size distributions. We present an approach where the exact size-broadened profile is obtained by averaging the interference function with a lognormal size distribution of spherical crystallites. We show that obtained size-broadened profile can be successfully modeled by a combination of Gaussian and Lorentzian functions, which permits for an analytical convolution with strain and instrumental profiles in Rietveld programs. This model can successfully fit "super-Lorentzian" line profiles that originate from a large dispersion of crystallite sizes

Formation and Characterization of NiFe2O4

Synthesis of nickel ferrite, NiFe204, was performed applying the thermal treatment of the corresponding mixed metal hydroxides or the solid state reaction between NiO and a-Fe203. The samples were studied by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mčssbauer spectroscopy. Ball-milling of NiFe204 caused a decrease of hyperfine magnetic fields corresponding to Fe3+ ions in tetrahedral and octahedral sites, an increase of the Mossbauer spectral line widths, as well as a slight increase of isomer shifts. It was supposed that the ball-milling of NiFe204 had more influence on the degree of inversion than on other structural properties of the spinel. It was found that the heating temperature, and not the heating time, had the ultimate effect on NiFe204 microstructure. Samples heated up to 500 °C showed a pronounced size-correlated diffraction line broadening, corresponding to the coherent domain size of about 13 nm, and rather small crystalline disorder. Samples heated at temperature s above "" 1000 °C had much larger crystallites, exhibiting very small disorder

Formation and Characterization of NiFe2O4

Synthesis of nickel ferrite, NiFe204, was performed applying the thermal treatment of the corresponding mixed metal hydroxides or the solid state reaction between NiO and a-Fe203. The samples were studied by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mčssbauer spectroscopy. Ball-milling of NiFe204 caused a decrease of hyperfine magnetic fields corresponding to Fe3+ ions in tetrahedral and octahedral sites, an increase of the Mossbauer spectral line widths, as well as a slight increase of isomer shifts. It was supposed that the ball-milling of NiFe204 had more influence on the degree of inversion than on other structural properties of the spinel. It was found that the heating temperature, and not the heating time, had the ultimate effect on NiFe204 microstructure. Samples heated up to 500 °C showed a pronounced size-correlated diffraction line broadening, corresponding to the coherent domain size of about 13 nm, and rather small crystalline disorder. Samples heated at temperature s above "" 1000 °C had much larger crystallites, exhibiting very small disorder

Diffraction Line Broadening - Nuisance or Lattice- Imperfections Fingerprints

Diffraction lines are broadened for two reasons: instrumental configuration and physical origins. The latter yields information on materials microstructure. The complete process of line-broadening analysis is discussed, beginning with experimental procedure s and a correction for instrumental broadening. In the analysis of the physically broadened line profile, the main emphasis is given to the widely used methods of separation of size and strain broadening: the Warren-Averbach approximation and integral-breadth methods. The integral-breadth methods are collated and their reliability discussed. Close attention is given to an assumed Vcigt-function profile shape for both size-broadened and strain-broadened profiles because it is shown that a Voigt function fits satisfactorily the physically broadened line profiles of W and MgO obtained by the Stokes-deconvolution method. The subsequent analyses of broadening are performed by using the Warren-Averbach and »double- Voigt« approaches and results are compared