Physical properties of niobium boride phases

Conclusions

• 1. Some physical properties of four boride phases in the system Nb-Bwere investigated.

• 2. It was establisned that these properties obey certain laws: the electrical resistivity and thermal expansion decrease with an increasing amount of boron in the boride phases.

• 3. A decisive influence on the electrical conductivity of the compounds investigated is exerted by the character of their Me-B bond; the electrical conductivity data obtained in this investigation have shown that the character of the Me-B bond is the same for all these phases.

• 4. The relationships established have been explained in the light of the electronic and atomic structures of these compounds: increasing the amount of boron results in the formation of stronger bonds. Bond saturation on transition from lower borides to higher produces a “freer” conduction band: the carrier concentration (n^*) decreases.