Comparative high pressure Raman study of boron nitride nanotubes and hexagonal boron nitride

High pressure Raman experiments on boron nitride multi-walled nanotubes show that the intensity of the vibrational mode at ∼1367 cm−1 vanishes at ∼12 GPa and it does not recover under decompression. In comparison, the high pressure Raman experiments on hexagonal boron nitride show a clear signature of a phase transition from hexagonal to wurtzite at ∼13 GPa which is reversible on decompression. These results are contrasted with the pressure behavior of carbon nanotubes and graphite.