By using an ab initio local-density approach and considering the defect locations of substitutional sites and mid-plane sites in the hexagonal boron nitride graphite structure, the defect formation energies of N, O, C ions in h-BN ceramic, and then the ionic conductivities, were calculated. Upon comparing with the experimental results, it was found that the main contribution of ionic conductivity was due to the O ionic defects. At high temperatures, no loss peak was observed in the measured dielectric loss spectrum, because the large conduction loss could obscure the loss peaks, which reflected the intrinsic dielectric relaxation. By eliminating the conduction loss in the measured dielectric loss, the loss peaks could be recovered.

Calculation of the Ionic Conductivity of h-BN and its Effect on the Dielectric Loss. X.Chen, Y.Cheng, X.Xie, W.Feng, K.Wu: Journal of Physics D, 2007, 40[3], 846-9