Ternary nitrides

Although there are several hundred biaary nitrides, only a relative few ternary bimetallic metal nitrides are known (6). A group of ternaries of the composition where M is an alkah, alkaline-earth, or a rare-earth metal and M is a transition or post-transition metal, have been synthesized (6). 

Phosphides. Compounds of phosphoms containing the more electropositive elements are generally called phosphides. A large number of binary phosphides as well as many ternary mixed-metal phosphides, metal phosphide nitrides, etc, are known. Some binary phosphides, such as those of nickel, exhibit a variety of stoichiometries (Ni P, Ni P2, Nq2P5, Ni2P, Ni P, NiP, NiP2, NiP ), whereas others, such as aluminum, form only one (AlP). Metalloids such as B and Si also form phosphides. 

Cubic Ternary nitrides with anti-Cap2 structure, e.g. BeLiN, AlLi3N2, TiLi5N3, NbLi7N4, and CrLi9N5... 

The crystal chemistry of metal nitrides has been reviewed and there have recently been some intriguing developments in our understanding of the stoichiometries and structures of ternary and quaternary metal nitrides. 

Ternary Nitrides as Diffusion Barriers. Barrier layers with good step coverage and low resistivity are formed from ternary nitrides with various compositions Ti-Si-N, W-Si-N, and W-B-N. They are deposited by MOCVD with deposition temperatures between 300 and 450°C. Complete step coverage is obtained on reentrant features as low as 0.25 micron with an aspect ratio of 4.0.Pi]... 

Smith, P. M., et al., Chemical Vapor Deposition of Ternary Refractory Nitrides for Difiusion Barrier Applications, Proc. 13th. Int. Conf. on VLSI Multilevel Interconnections, Sandia National Labs., Albuquerque, NM (1996)... 

Figure 7.15 (a) Enthalpy of formation of ternary oxides and nitrides from their binary constituent compounds as a function of the ratio of ionic potential [16]. Reprinted with permission from [16] Copyright (1997) American Chemical Society, (b) Gibbs energy of the oxide-sulfide equilibrium for group 1 and 2 metals at 1773 K as a function of the optical basicity of the metal. 

In another example, the high temperature reaction of calcium and strontium sub-nitrides with molybdenum foil has also recently been claimed to produce novel molybdenum ternary nitride oxides which contain isolated [MoN4] tetrahedra in an ordered sub-lattice of and anions. High temperature-high pressure syntheses are also yielding novel metastable structures, such as the spinel analogues mentioned previously. There is therefore an ever-increasing base of nitrides and oxynitrides with diverse structures and potential catalytic interest. 

Although the literature often indicates catastrophic reactions of fluorine with oxides, nitrides, carbides, silicides, borides and the like, many such species may be reacted under controlled conditions to produce oxyfluorides, nitro-fluorides such as TINF, ZrNF, HFNF, ThNF, and UNF, and other interesting ternary systems. 

Rogi, P. and J.C. Schuster Phase Diagrams of Ternary Boron Nitride and Silicon Nitride Systems, ASM International, Materials Park, OH. 1992. 

Recent developments in the synthesis, structures, and properties of ionic/covalent ternary nitrides are reviewed. A description, including synthetic conditions, is given of preparative methods reported in the literature. Solid state synthetic reactions from binary nitrides as well as novel synthetic approaches such as amide synthesis and ammonolysis of ternary oxides are described. Examples of common structure types as well as electronic and magnetic properties are discussed. 

Although the distinction is not always clear, ternary nitrides (and nitrides in general) often are classified into two groups (1) intermetallic-type and (2) ionic/covalent-type. Intermetallic nitrides are those in which metal-metal (M-M) interactions are dominant and where the nitrogen atoms are interstitial within the metal array.3 Because these phases are stabilized by M-M interactions, the structure and physical properties are similar to those of many other metallic systems, such as alloys, metals, and... 

Table 8.1 Reactions commonly used in ternary nitride synthesis...

Most known quaternary nitrides contain lithium and are synthesized by reacting a lithium-containing ternary nitride with a metal or metal nitride (Table 8.1, Equation 5). Many of the quaternary nitrides reported also may be synthesized by the reaction of the elements either under N2 or with Li3N. Very few true quaternary compounds are known, and further studies of ternary systems are needed before advances in the synthesis of quaternary systems can be realized. 

Lithium-containing ternary nitrides most commonly form anti-fluorite related structures (anti-CaF2).9 Nitrogen occupies the 8-coordinate calcium... 

Figure 8.2 Structure of LiMN2 (M = Mo,W) and a-MnWN2 Examples of ternary nitrides containing Mn/Li octahedra and Mo/W trigonal prisms. Gray = Manganese/Lithium, Black = Molybenum/Tungsten, White = Nitrogen.

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