Triboluminescence of crystals and suspensions of inorganic salts of lanthanides

It is found that the triboluminescence spectra of crystalline hydrates of inorganic salts of Ln(3+) (Ce3+, Pr3+, Gd3+, Eu3+, Tb3+, and Dy3+) during mechanical trituration and ultrasonic treatment (22 kHz) of crystal suspensions in perfluorodecalin (in the sonotriboluminescence) exhibit gaseous and solid-state components. The first component contains emission lines of N2 in an electric discharge. The spectrum of the second component coincides with the photoluminescence spectrum of the crystals, including ions that cannot be excited due to the absorption of emission from N-2: Ce3+, Pr3+, and Gd3+. Among the different salts of Ln(3+), the highest intensity of luminescence is observed in sulfates; the highest yields of tribo- and sonotriboluminescence are characteristic of the Ce3+ salts. The triboluminescence of Ln(3+) nitrates is not registered. Possible mechanisms of excitation of the Ln(3+) ions are discussed. The main source of the solid-state component of the triboluminescence of Ln(3+) salts is assumed to be the electroluminescence typical of crystalline phosphors. It is shown that, along with lines of N-2, the spectrum of the triboluminescence observed in the atmosphere of He, Ar, and O-2 contains lines of these gases.