Strong deep-blue photoluminescence of mesographite boron nitride

Amorphous boron nitride (a-BN) powder was prepared by mechanical milling of hexagonal BN. Annealing the a-BN between 600 and 1200degreesC produced turbostratic BN (t-BN) and mesographite BN (m-BN) with different degrees of three-dimensional order (DTDO). The photoluminescence (PL) of the BN samples was investigated using 325 run laser excitation. The a-BN and t-BN emit continuums with a maximum near 340 nm. The m-BN samples that have three-dimensional order show deep blue PL bands. The positions of the bands change with lattice constants, while the PL intensity increases firstly with increasing DTDO then decreases after reaching a maximum. The strongest PL band is observed at 413 nm in one of the m-BNs prepared at an annealing temperature of I 100 degreesC. It is suggested that the bands are related to structural defects in the m-BNs.