Current State on B,C,N Compounds of Calcium and Lanthanum

A remarkable variety of compounds in the Ca-(B,C,N) system has opened a window for research in related fields. With the elements boron, carbon and nitrogen, substance classes such as borocarbides, boronitrides, and carbonitrides can be considered to contain anionic derivatives of binary compounds B4C, BN, and C3N4. Until now, most compounds in these substance classes have been considered to contain alkali, alkaline-earth, or lanthanide elements. Lanthanide borocarbides are known from the work of Bauer [1]. Lanthanide boronitrides represent a younger family of compounds, also assigned as nitridoborates [2] following the nomenclature of oxoborates. 

The compounds that are being reported here are mostly those with combined anions, such as BN anions in nitridoborates. On the other hand, we know of compounds with mixed anions, like the well-known Ti(N,C) in which anions share the same lattice site, or NbBN with separate B and N sublattices. How can these compounds be explained in comparison with compounds having C-N or B-N bonding Are there separate strategies for their synthesis, what are the differences in stability, what are their properties, and what are their structures like These and some other questions will be discussed, mainly for Ca-(B,C,N) and La-B-N systems. 

Problems and Pitfalls of some Calcium Compounds with (mixed) B,C,N Anions 

In the past, there was quite a lot of confusion regarding the true nature of some alkaline-earth compounds. Several boride, nitride, and carbide compounds, as well as some mixed species, especially of calcium, were in doubt or at least subject to some ongoing discussion. For example, the phase relationships and structures of CaC2 phases I-IV were not well understood. The three nitride 

Recently, some hght was shed on these and other compounds as well as on their structures and properties. Today it may be considered that some of the mistakes made earher could have been avoided by the availability of elements or compounds of higher purity, and thereby have prevented the incorporation of unexpected impurities. In this context it is important to note some experimental principles of solid-state synthesis that should be considered In solid-state synthesis, great attention should be always dedicated to the purity of the starting materials, the purity of the container material (and gas atmosphere) used in the reaction, and the control and adjustment of the reaction conditions in order to finally obtain a high yield product 

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I 8 Current State on (B,C,N) Compounds of Calcium and Lanthanum Energy... 

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