Nitrides, Phosphides, and Arsenides

Nitrides, Phosphides, and Arsenides. The phase diagram for the Cr-N system between 900 and 1350°C has been constructed and thermodynamic relationships in this system have been calculated. These latter studies indicated the extreme sensitivity of the kinetics of Cr-N reactions to oxygen impurity.  

CrP has been synthesized by reaction of the elements at pressures of 15— 65 kbar. The crystal structure involves chromium atoms co-ordinated by six phosphorus atoms in a distorted octahedral arrangement with Cr—P = 232—239 pm. CrMAs (where M = Co or Ni) have been characterized by A -ray diffraction spectra.  

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The M(14) nitrides, phosphides, and arsenides are materials with industrially useful properties, and while these are fascinating areas and although there is a wealth of literature relating to these compounds they do not fall within the scope of this article. Some materials or methods of preparation that relate to this group of compounds that are new are covered because they are of more general interest. 

Nitrides, phosphides and arsenides Halides, oxohalides and complex halides Oxides of nitrogen Oxoacids of nitrogen... 

Nitrides, phosphides and arsenides Halides and oxohalides Oxides and oxoacids Phosphazenes Sulfides and selenides Aqueous solution chemistry... 

Debye temperatures Od in K. The values for the nitrides, phosphides and arsenides were derived from specific-heat measurements, those of ref. (g) from the elastic properties and those of ref. (e) from thermal expansion at 20-750°C according to the formula... 

The term S] is defined by the authors as an ionicity factor and assumes a value of 0.5 for oxides and silicates, 0.75 for halides, 0.40 for calcogenides, 0.25 for phosphides and arsenides, and 0.2 for nitrides and carbides (Z is the anion charge). Equation 1.94 is based on the thermal expansion data listed in table 1.15. 

The difference in heat of formation is even more marked between the nitrides and phosphides. By the same reasoning as for the oxides and sulphides, the alkali phosphides (where r+ is large) should have higher heats of formation than nitrides while the nitrides, with the exception of Li3N, cannot be prepared, the phosphides and arsenides of the alkali metals are fairly stable compounds. 

II. Antimonides, Arsenides, Carbides, Fluorides, Hydrides, Nitrides, Phosphides, and Sulfides... 

Bulk moduli for ambient conditions (with index o ) are listed in Tables 10.7 for elements, SlO.l for compounds MX, S10.2 for MX2, S10.3 for MX3, S10.4 for binary oxides, S10.5 for binary nitrides, S10.6 for binary borides, S10.7 for binary carbides and silicides, S10.8 for binary phosphides and arsenides, S10.9 for ternary oxides and coordination compounds, SIO.IO for molecular substances and polymers, SlO.l 1 for characteristics of polymorphous modifications of elements and the MX compounds, S10.12 for various phases ofMX2 crystals. 

These are usually reactions of anhydrous transition and B metal halides with dry alkali metal salts such as the sulphides, nitrides, phosphides, arsenides etc. to give exchange of anions. They tend to be very exothermic with higher valence halides and are frequently initiated by mild warming or grinding. Metathesis is... 

Interstitial structures are not possible for the larger P and As atoms, and apart from a few cases such as LaP, PrP, and GeP with the NaCl structure there is usually little similarity between nitrides and phosphides (or arsenides). Compare, for example, the formulae of the nitrides and phosphides of Mo and W M02N, W2N, MoN, and WN, but M03P, W3P, MoP, WP, M0P2, and... 

Nitrides, Phosphides, Arsenides, and Related Compounds. The presence of imperfections in the metal sub-lattice of cubic tantalum nitride indicated by neutron diffraction experiments has been confirmed by density measurements the results are consistent with the stoicheiometry Tao.saN. The phase diagram of the Ta-N system has been investigated. The dissociation pressure of non-stoicheiometric niobium mononitride has been measured,and the structures of Nb32N3, Ni2Ta4N, " TagN, and TaagNj have been determined. 

Chapter 14 Nitrides, phosphides, arsenides, antimonides and bismuthides 401... 

U.S. Bureau of Mines Bull. 672, 674, and 677. Bulletins 672 and 674 cover the elements, binary oxides and binary halides in a very complete fashion. Bulletin 677, summarizes the values from Bulletins 672 and 674, and adds a modest selection of tables for arsenides, antimonides, borides, carbides, carbonates, hydrides, nitrides, phosphides, selenides, silicates, silicides, sulfates, sulfides and tellurides. The coverage of these added compound types, however, is far from complete for example, there are no tables for PbS04, SnS04, GaS and Li2S. The only ternary compounds included are the carbonates, sulfates and silicates, and no quaternary compounds are listed except for a limited number of hydrated compounds. Only brief references are given to the data sources, without attempt to explain the choice between conflicting values. 

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