Ternary ceramics

Abstract Refractory oxides encompass a broad range of unary, binary, and ternary ceramic compounds that can be used in structural, insulating, and other applications. The chemical bonds that provide cohesive energy to the crystalline solids also influence properties such as thermal expansion coefficient, thermal conductivity, elastic modulus, and heat capacity. This chapter provides a historical perspective on the use of refractory oxide materials, reviews applications for refractory oxides, overviews fundamental structure-property relations, describes typical processing routes, and summarizes the properties of these materials. 

This last statement has far-reaching implications. If the band gap, usually denoted by Eg, lies somewhere between 0.02 and 3 eV, the material is considered to be a semiconductor. For higher values of Eg, the solid is considered an insulator. Said otherwise, if all the electrons are used in bonding, none is left to move freely and conduct electricity. Table 2.6, in which the band gaps of a number of binary and ternary ceramics are listed, clearly indicates that most ceramics are insulators. 

And while this is clearly not a ceramics handbook, I have included many important properties of binary and ternary ceramics collected over 10 years from numerous sources. In most chapters 1 also include, in addition to a number of well-tested problem sets with their numerical answers, worked examples to help the student through some of the trickier concepts. Whenever a property or phenomenon is introduced, a section clearly labeled experimental details has been included. It has been my experience that many students lacked a knowledge of how certain physical properties or phenomena are measured experimentally, which needless to say makes it rather fruitless to even try to attempt to explain them. These sections are not intended, by any stretch of the imagination, to be laboratory guides or procedures. 

The salient properties of this layered ternary ceramic are good damage tolerance, good machinabUity, low density and excellent thermal shock and oxidation resistance. Such unique properties make it possible to use Ti3AlC2 in structural components for high-temperature applications and as oxidation-resistant coatings. 

B-N-Ti ternary ceramics are either deposited by thermal CVD from BCI3, TiC, NH3, and H2 on graphite substrates [20, 21], or by sputtering boron and titanium in an Ar/N2 atmosphere to coat a molybdenum substrate [22]. 

M.W. Barsoum, T. El-Raghy, The MAX phases unique new carbide and nitride materials — ternary ceramics turn out to be surprisingly soft and machinable, yet also heat-tolerant, strong and hghtweight. Am. Sci. 89 (2001) 334—343. 

Layered ternary ceramics (LTCs), an extension of the M4Yphase [I], have recently been described [2], LTCs such as phases (where Mis an... 

High-temperature corrosion of layered ternary ceramics 257... 

Table 9.1 Summary of crystal structural parameters of several representative layered ternary ceramics...

Table 9.3 Summary of typical methods for synthesizing three representative layered ternary ceramics. C and R denote compound and reference, respectively... 

High-temperature corrosion of iayered ternary ceramics... 

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