NdSe

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The entropy of NdSe(g) at 298.15 K was calculated to be 5°(NdSe, g, 298.15 K) = 277.5 J K mol by Kovalevskaya, Sidorenko, Lysenko, and Fesenko [75KOV/SID]. The entropy value is not selected because all parameters required for the calculation using statistical mechanics were estimated. 

Na2S04[lll] SODIUM SULFATE (III) 1150 NdSe NEODYMIUM MONOSELENIDE 1193... 

An analysis of the published data on the electrical properties of the alloys StnSe-NdSe and EuSe-LaSe is used to propose energy band schemes for these substances. The absorption spectra of films of EuS, EuSe, and of EuSe-LaSe alloys, obtained by thermal evaporation under vacuum, are presented, as well as the diffuse reflectance spectra of EuS and EuSe powders. These optical studies are used to suggest which electron transitions ate responsible for the light absorption in these semiconductor compounds. 

To ejq)lain the phenomena which have been observed, Reid et al. suggested that, at 11-13% NdSe in SmSe, chains of neod3rm-ium ions of appreciable lengtii are formed, along which the motion of electrons may occur. 

With an increase in the Nd content in the Smi xNdxSe alloy, an impurity level lying 0.4 eV below the bottom of the conduction band appears in the forbidden band of SmSe. The bottom of the conduction band is lowered by an interaction with the impurity when its concentration is increased, whereas the local levels are split, forming an impurity band. At 13% NdSe in SmSe, the conduction process commences along the Nd chains and the electrical conductivity increases suddenly, as a result of an increase in the mobility of the electrons. 

The picture may be complicated by partial transitions of electrons from the level to the level to form deeper states. This may e mlain, in particular, the virtually complete absence of a temperature dependence of the electrical conductivity for an alloy with 2% NdSe. 

Doping EuSe with additions of LaSe or GdSe produces a shallow donor d level. A transition from the latter to the level of Eu does not occur because this state is located deeper, energy-wise, than Excitation of the electrons into the conduction band therefore takes place at lower temperatures than for SmSe-NdSe alloys. Thus, the electrical conductivity in the case of low concentrations of trivalent RE ions is due to the electrons in the conduction band. At higher concentrations, chains of La or Gd ions form as in the preceding case. 

NdSej, NdSe, 9 P4/nmm 0=4,133 c=8,807 2 CujSb Einkristalle, Struktur komplett 66E113 ... 

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