Structure, luminescence and mechano-optical properties of strontium aluminate doped with europium and dysprosium ions

Abstract

Photoluminescence spectra and kinetics of mechanoluminescence of finely dispersed powder of SrAl2O4:(Eu2+, Dy3+) and Sr4Al14O25:(Eu2+, Dy3+) phosphor was investigated. Photoluminescence was excited by nanosecond laser pulses with a wavelength of λ = 355 nm and by a group of cw lasers with different wavelengths (λ=355, 404, 440, 530 nm). Photoluminescence of the materials has been revealed in the long-wave (550 to 750 μm) spectral region, which is indicative of the existence of corresponding energy levels of Eu2+ions. It was shown that, at low power density, a single wide broadened line of photoluminescence was observed. As radiation power density is increased, additional photoluminescence lines begin to appear. The microstructure of the powders has been investigated with the scanning electron microscope. It has been found that the powder consists of microparticles (granules) of the sizes up to 100 μm. The microparticles show a granular structure, the grain size being as large as 25 μm. Mechanoluminescence was initiated by an acoustic wave generated by short laser pulses. A mechanism of mechanoluminescence excitation has been suggested. It has been concluded that mechanoluminescence of SrAl2O4:(Eu2+, Dy3+) is excited owing to activation of the traps during their interaction with the electric fields of moving grain boundary dislocations as the result of grain boundary sliding under deformation of microparticles on impact.