Solid state transitions during the growth of silicon by chemical vapour deposition

The crystalline-amorphous transition during chemical vapour deposition of silicon has been studied. Results are reported for growth from 2.3 vol% SiH4 177 in hydrogen at atmospheric pressure. From optical measurements two after-growth phenomena were discerned, viz. a change in emissivity below T = 6780C and a change in optical thickness below T = 7720C. Consistent with the mechanism of formation the observed optical phenomena are connected with differences in the structure of the deposited material and the related solid state transitions a-Si:H + a-Si + c-Si

Phase Formation of Ca-alpha-sialon by Reaction Sintering

In this study the reaction sintering route for the formation of Ca-a-sialon with a composition on the line Si3N4/CaO · 3AlN (Ca0.8 Si9.6 Al2.4 O0.8 N15.2, m = 1.6, N = 0.8) has been investigated. This is compared with the hot-pressing of Ca-a-sialon and the reaction sintering of Y- or lanthanide-a-sialons. The reaction follows the same sequence: first, the formation of a Ca-rich a-sialon phase (m = 1.9) which is gradually transformed to a Ca-a-sialon with a lower Ca concentration (m = 1.2). The gehlenite phase (Ca2Al2SiO7, melilite group) is observed as an intermediate product. A potential advantage of Ca-a-sialon over Ln-a-sialon Full-size image is liquid phase formation at a lower temperature, which has a positive influence on the processing temperature. Moreover, Ca is cheaper than the lanthanides. The solubility of Ca in the a-sialon is in agreement with values found in the literature

Eu-doped barium aluminium oxynitride with the ß-alumina-type structure as new blue-emitting phosphor

Attractive new blue-emitting phosphors for use in low-pressure mercury gas discharge lamps are synthesized by Eu-substitution in the barium aluminum oxynitride host lattice with the -alumina-type structure. The emission spectra of these phosphors for 254 nm excitation show a band at about 450 nm with a shoulder at higher wavelength. The maximum quantum efficiency of these materials is about 85–90% just like commercial BaMgAl10O17:Eu with the -alumina type structure. The nonoptimized oxynitride phosphors are more sensitive to oxidation (at 873 K) and to short-term depreciation due to 185 nm irradiation compared to commercial BaMgAl10O17:Eu. However, the maintenance of the oxynitride phosphors in single component fluorescent lamps is improved. Calculations indicate that by using these phosphors in tricolor fluorescent lamps instead of BaMgAl10O17:Eu with the -alumina type structure, the color rendering index will improve while the lumen output remains high

Ce3+, Eu2+ and Mn2+-activated alkaline earth silicon nitride phosphors and white-light emitting LED

The invention refers to an alkaline earth silicon nitride phosphor of the MSiN2 type that is activated by Ce3+ and/or Eu2+ and/or Mn2+ ions. A preferred embodiment of the phosphor is defined by the general formula MSiN2:A, wherein M is a divalent metal ion, especially Mg, Ca, Sr, Ba, Be and/or Zn, and A is an activator chosen from the group Ce3+, Eu2+ and/or Mn2+. A preferred application for this phosphors is a white-light emitting LED using the phosphor for conversion of radiation

Ce3+, Eu2+ and Mn2+-activated alkaline earth silicon nitride phosphors and white-light emitting LED

The invention refers to an alkaline earth silicon nitride phosphor of the MSiN2 type that is activated by Ce3+ and/or Eu2+ and/or Mn2+ ions. A preferred embodiment of the phosphor is defined by the general formula MSiN2:A, wherein M is a divalent metal ion, especially Mg, Ca, Sr, Ba, Be and/or Zn, and A is an activator chosen from the group Ce3+, Eu2+ and/or Mn2+. A preferred application for this phosphors is a white-light emitting LED using the phosphor for conversion of radiation

Synthesis and property evaluation of novel vitreous and nanocrystalline oxynitrides (spensalon)

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