Observation of spontaneous polarization of tourmaline

Since Tetsujiro kubo indirectly found the spontaneous polarization of tourmaline through absorbing copper ions in copper sulfate aqueous solutions in 1980s,there is no other evidence to demonstrate the existence of the spontaneous polarization in tourmaline.It was ound that after a tourmaline particle was bombarded by electron beams,a spot appeared on the surface of the sample,and that one half of the spot was brighter than the other half under scanning electron icroscope.After touraline was treated for 2h at 1223K and then bombarded by electron beams,the bombardment spot did not appear because the crystal structure of tourmaline is destroyed.The existence of the bombardment spot accounts for the spontaneous polarization.The shape and brightness of the bombardment spot not only shows the existence of a surface electric filed induced by spontaneous polarization.but also the relation with the direction of the crystal plane of tourmaline.