Nitrides group IIIA

In this chapter, a brief summary of studies that made use of calorimetry to characterize compounds comprising group IIIA elements (zeolites, nitrides, and oxides catalysts) was presented. It was demonstrated that adsorption microcalorimetry can be used as an efficient technique to characterize the acid-base strength of different types of materials and to provide information consistent with the catalytic data. 

Salt-like or ionic nitrides, in which N forms primarily ionic bonds to alkali metals, rare earth metals, and members of group IIIA. Although actinide nitrides are also included in this grouping, they may equally well be classified as metallic. Compounds in this group are readily hydrolyzed and must thus be protected from moisture. 

Today, it has been fairly well established that the layered ternary carbides and nitrides with the general formula +iAX,j, and where n = 1,2 or 3, M is an early transition metal, A is an A-group element (mostly group IIIA or IVA), and X is either C or N, represent a new class of solids [1, 2]. These phases are layered, with M +iX layers interleaved with pure A-group element layers. 

Table 7.1 lists most of the known MAX phases - most of which were discovered by Nowotny et al. [10] during the 1960 s - together with their lattice parameters and theoretical densities. The A-group elements are mostly IIIA and IVA, and all but five compounds are 211s. The most versatile element is Al, as it forms nine compounds, including two nitrides, one 312 phase, and four 413 phases. Ga also forms nine 211 phases, six of which are carbides and three are nitrides. 

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