Neutron damage of hexagonal boron nitride: h-BN

Abstract

Hexagonal boron nitride (h-BN) was neutron damaged at an integral flux of 2.40 × 1012 n cm−2 s−1 for 1, 2, 3 and 4 h. The h-BN samples undergo a transition from sp2 to sp3 hybridization as a consequence of the neutron induced damage with the formation of cubic boron nitride (c-BN) spots, as suggested both by FT–IR and Raman spectroscopy. In addition to c-BN, also a certain degree of amorphization is achieved by h-BN already at the lowest neutron fluence of 8.64 × 1015 n cm−2 as clearly evidenced by Raman spectroscopy. The Wigner or stored energy to the radiation-damaged h-BN samples was studied by DSC and also in this case there was a clear evidence that the neutron damage was partly irreversible and insensitive to the thermal annealing up to 630 °C. Electron spin resonance (ESR) was employed to further study the structural defects induced by the neutron bombardment of h-BN. Two kinds of paramagnetic defective structures centered on 11B atoms were identified.