Physical rare earth carbides

Adachi, G.-Y., Imanaka, Nv Zhang, F. Rare earth carbides, in Gschneidner Jr., K.A., Eyring, L., editors. Handbook on the Physics and Chemistry of Rare Earths, vol. 15. Amsterdam North-Holland 1991, chap. 99. 

Ternary rare-earth-carbon-haJide compounds 8. Physical properties of the rare earth carbides... 

Physical properties of binary rare earth carbides and their solid solutions... 

Physical properties of ternary rare earth carbides References... 

In this work, we shall give a review of the fundamental research on the rare earth carbides by focussing our attention on the phase diagram and the thermodynamics concerned with the formation of carbides, and on the crystal structures and the chemical and physical properties. In addition, we also pay attention to those topics that need further investigation. 

Drs. G.-y. Adachi, N. Iraanaka, and Z. Fuzhong review the rare earth carbides (chapter 99) emphasizing the thermodynamics, phase diagrams, crystal structures, and physical properties. The binary rare earth carbides present an exceptionally wide range of compositions and structures both as solids and gas-phase molecules. More complex carbides with additional metal and non-metal components also receive attention. 

In this section, I focns on the ternary rare earth boride compounds that have particnlar interest for their stmctural features or physical properties. Rare earth borocarbides are described in a separate section, after the section on rare earth carbides. 

These same researchers also explored the efficacy of the individual rare earths as nodulizers (17). They concluded, by their ability to produce nodular iron having adequate physical properties without excessive iron carbides present, that cerium was the most effective of the four rare earth elements (lanthanum-neodymium) evaluated as nodulizers. They reported that it required 1.5 times as much neodymiun or praseodymium and three times as much lanthanum as cerium to yield equivalent results. 

Further, it was demonstrated that the introduction of cerium, as mischmetal, in proper amounts was effective in eliminating iron carbides which cause deterioration in physical properties (21). The elimination of iron carbides in thin sections by proper use of the rare earths represents a major contribution to the industry. Different researchers have agreed that there is an optimum percentage for this rare earths addition, which they reported as cerium only, from 0.01% to 0.02% cerium (from about 0.02% to 0.04% total rare earths) that provides this increase in nodule count and control of iron carbides when used in conjunction with magnesium nodulizers (see Figure 9). 

In the so-called interstitial nitrides the metal atoms are approximately, or in some cases exactly, close-packed (as in ScN, YN, TiN, ZrN, VN, and the rare-earth nitrides with the NaCl structure), but the arrangement of metal atoms in these compounds is generally nor the same as in the pure metal (see Table 29.13, p. 1054), Since these interstitial nitrides have much in common with carbides, and to a smaller extent with borides, both as regards physical properties and structure, it is convenient to deal with all these compounds in Chapter 29. 

Altounian, Z., Chan, X., Liao, L. X., Ryan, D. H. Strom-Olsen, J. O. (1993). Structure and magnetic properties of rare earth iron nitrides, carbides and carbonitrides. Journal of Applied Physics, 73, 6017-22. 

Yupko, V.L., G.N. Makarenko and Yu.B. Paderno, 1974, Physical properties of carbides of rare earth metals, in Refractory Carbides, ed G.V. Samsonov (Consultants Bureau, New York) p. 251,... 

This work includes a number of the more important physical and chemical properties of the nine transition elements included in Groups 4, 5, and 6 of the 4th, 5th, and 6th periods. The three actinide systems, Th-C, U-C, and Pu-C, have also been discussed. While this limited selection does not include all of the high melting carbides (many Group 3 and rare earth systems fall into this category), it does include the more refractory and the more useful ones. Besides, only for these systems has sufficient information been generated to make a critical review worthwhile. 

This chapter briefly reviews what is known of the rare earth borides, carbides, and nitrides. This review wonld particularly like to showcase interesting features of the crystal structure and intriguing physical properties ranging ft-om the fundamental to the very applicable, with an emphasis on recent emerging results in important functionalities such as magnetism, thermoelectricity, and superconductivity. 

While there are myriad helpful reviews, there has previously been no up-to-date, one-stop review article available for any one of the rare earth borides, carbides, and nitrides, and in this sense I feel tiiis chapter, which contains brief summaries, valuable references as gateways to further detailed information, and a focus on timely topics of all three systems, will be particularly useful. A section is included at the end summarizing the particularly notable physical properties described in each section. 

I would like to briefly sum up some of the notable physical properties of the rare earth borides, carbides, and nitrides described in the previous sections. 

To suimnarize, the rare earth borides, carbides, and nitrides have yielded interesting compounds with striking features in their crystal structures and physical properties, and also successfiil applications. They also appear to be systems that are amenable to materials design. This is an important direction to strive for in the current world where natural resources are limited, namely, to highly functionalize materials that are mainly composed of abundant light elements through the innovative use of a small amount of rare element. 

Holleck, H., 1973, Perowskite Carbides and Borides of the Transition Metals, paper presented at the 4th Intern. Conf. on Solid Compounds of Transition Elements, Geneva, landelli, A. and A. Palenzona, 1979, Crystal chemistry of intermetallic compounds, in Handbook on the Physics and Chemistry of Rare Earths, Vol. 2, eds. K.A. Gschneidner, Jr. and L. Eyring (North-Holland, Amsterdam) pp. 1-54. 

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