Abstract
The low-temperature luminescence of bulk hexagonal boron nitride (hBN) powder and boron nitride multiwall nanotubes (BNNTs) was investigated. It was found that, apart from the well-known luminescence at 300 nm and 400 nm, a broad luminescence band at 450 nm appears under low temperatures (8 K), and that heating the sample results in its quenching - at 190 K the luminescence intensity becomes negligible. The 450 nm luminescence is characterized with its own excitation band at 240 nm and is excited also at 270 nm and 350 nm. Besides, this luminescence can be excited through excitonic processes with light around 205 nm. The same features of 450 nm luminescence are observed in both the hBN and BNNTs.