Electrophysical Characteristics of $c$BN–NbN Composite Ceramics Doped with Al$_{2}$O$_{3}$, Si$_{3}$N$_{4}$, and SiC

Different additives' influence on electric conductivity of 'dielectric/conductor'-type composites (namely, polycrystalline cBN-based composites contained cBN as a dielectric phase and NbN as a conductor phase) is investigated.Investigated samples are obtained by the application of HPHT (high pressure-high temperature) sintering (P = 7.7 GPa, T = 2000°C).Electrical-resistance dependences on the temperature and applied voltage are measured for all samples.Obtained results' analysis shows that all sintered samples have a semiconductor nature of conductivity.It is interesting that addition dielectrics (Al2O3, Si3N4) as well as semiconductor (SiC) leads to the electric-conductivity improve (drop in electrical resistance) for cBN-NbN composites in some degree (despite the lower electrical conductivity of these substances).Alumina whiskers' addition to cBN-NbN composites leads to a more significant drop in electrical resistance compared to powder particles' addition (from 1.85 to 0.72 Ohm⋅cm for samples with whiskers (Al2O3w) and from 1.35 to 0.17 Ohm⋅cm for samples with Al2O3 powder).Hence, as con-