Crystal chemistry borides

A systematic approach to the crystal chemistry of borides is possible on the simple basis of atom size considerations, as well as the tendency of B to form covalent skeletons. 

The crystal chemistry of the borides is discussed in 6.7.2 according to this scheme. General methods of preparation, single-crystal growth and sintering of borides is considered, respectively, in 6.7.3, 6.7.4 and 6.7.5. 

Uncharacterized ternary and binary metal borides, lacking precise composition or crystal chemistry data (see Fig. 2, Table 2), are not covered in this context. Further-... 

Existence and Crystal Chemistry of Borides 6.7.2.1. Borides with Isolated Boron Atoms... 

Nickel atoms in BajNi B form distorted, puckered 3.6.3.6-kagome nets stacked in six layers perpendicular to the c axis. The densely packed framework of trigonal-Ni prisms again result in boron-pair formation, although Ba atoms are too large to be sandwiched between two Ni layers, and only four Ba can be accommodated within six Ni layers. Superconductivity is found for ( a, Sr, Ba)2pt9Bg borides with a structure related to Ba2Ni9Bfi and e o,B2 however, with respect to crystal chemistry and boron coordination, only the subcell is derived so far. 

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