Nitrides, quaternary

Takayama, T, M. Yuri, K. Itoh, T. Baba and J.S. Harris Jr. 2001a, Analysis of phase-separation region in wurtzite group Ill-nitride quaternary material system using modified valence force field model. J. Cryst. Growth 111, pp. 29-37. 

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. 

Carbonitride alloys, quaternary, 17 218. See also Carbonitrides Carbon nitride entries... 

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. 

There are a limited number of techniques used for the synthesis of ternary and quaternary nitrides. In fact, the vast majority of these nitrides have been synthesized using only two methods (1) the reaction of a metal nitride with a metal or another metal nitride and (2) the reaction of two metal powders with nitrogen gas or ammonia. The first method has been the most common approach (Table 8.1, Reaction 1). Since these reactions usually require high temperatures (1073-2073 K), the inductive effect is Used to effect product formation. Li3N is a favored starting material due to its stability and relatively low melting temperature (mp = 1086 K), which... 

Table 8.2 Synthetic conditions of ternary and quaternary nitrides... 

Upon additional alloying ternary carbonitrides quaternary carbonitrides are obtained. The group 4 and 5 transition metal carbides and nitrides are completely miscible except TiN-VC and ZrN-VC. Thus, modified material properties can be obtained (see also Section 9.2). Information on the properties of these carbides are still scarce," a few data are given in Figure 13 and Table 4. 

Recent developments in the field of CVD and PVD layers are multilayer coatings that consist of carbonitrides, carbides, nitrides, and oxides, whereas the trend goes into the use of ternary and quaternary carbonitrides such as Zr(C,N) and (Ti,Hf)(C,N) as well as mixed oxides such as Al203/Ti02, Al203/Ti02/Hf02. 

Ternary phases with structures different from those of the phases of the binary boundary systems are more the exception than the rule. Such phases have been reported in the systems Nb-Mo-N, Ta-Mo-N, Nb-Ta-N, Zr-V-N, Nb-Cr-N, and Ta-Cr-N. Information about ternary transition metal-nitrogen systems is often available for specific temperatmes only. This is even more the case for quaternary nitride systems, which play a role in the production of carbonitride cermets where quaternary compounds of the types (Ti,Mo)(C,N) and (Ti,W)(C,N) are of interest (see Carbides Transition Metal Solid-state Chemistry), as well as in layer technology where titanium nitride-based coatings of the type Ti(C,B,N) are prepared by magnetron sputtering. Layers consisting of ternary compounds of the type (Ti,Al)N and (Ti,V)N also have favorable properties with respect to abrasion resistance. 

More complex (ternary and quaternary) nitride ceramics can also be formed from polymeric precursors. Thermal decomposition of [CH3Si(N = C = N)i.5]n has been shown by N NMR to form NSi3 units when the protons are lost from the system during heating at 600-800°C (Gabriel et al. 1999). The product is an amorphous mixture of Si3N4 and carbon which reacts to form an amorphous Si-C-N ceramic phase. Similar studies have been carried out on the formation of Si-B-N ceramics from single phase... 

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. 

During their genesis all precursor derived ceramics pass through an amorphous state which in certain cases is stable up to the respective decomposition temperature. The propensity to crystaUize is strongest for the binary silicon and boron nitrides and carbides, while in particular quaternary materials out of the Si/B/N/C system show the strongest resistance towards crystallization. It is interesting to note that in any case investigated, so far, the amorphous multinary ceramics decompose into the binary border phases upon crystallization - crystalline ternary silicon boron nitrides or carbides are not known to date cf. [9]. 

Nitrides.— The solubility study of nitrogen in liquid lithium also yielded results on the thermal decomposition of solid lithium nitride. The problems encountered in the nitridation of Sr and Ca to the stoicheiometric M3N2 are explained by the presence of hydrogen in the starting metals, which leads to the formation of non-stoicheiometric nitride hydrides, until now assumed to be Ca2N and Sr2N. The so-called SrN, which is formed only in the presence of oxygen is, in fact, a NaCl-type cubic quaternary phase that is rich in N and of variable composition... 

A variety of other ternary and quaternary carbides and carhonitrides is especially interesting for use in metal cutting tools in the form of layers, and powder particles have been investigated recently for their specific heat, temperature and thermal conductivity [66]. The behavior of the heat conductivity of most of these compounds is similar to that of the group IVB carhonitrides for (near) stoichiometric composition showing a positive curvature of heat conductivity as a function of temperature. Interestingly, however, Nb- and Mo-containing ternary titanium carbides and nitrides and quaternary titanium carhonitrides show a hnear behavior in the same temperature interval. 

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