ИСТИНА

The main purpose of the current study is the complex investigation of luminescent properties of undoped langasite and langatate crystals. The crystals were grown by the Czochralski method in iridium crucibles in the mixture of argon and oxygen (Ar +(2%) O2), polar cut samples were used. The reflection, transmission, luminescence and luminescence excitation spectra as well as emission decay characteristics of crystals were measured using laboratory setup of MISiS, SINP MSU and IP TU as well as using synchrotron radiation at the branch-line FINEST at MAX-lab, Lund. At least two emission bands are observed in the luminescence spectrum of the langatate. The bands are close to each other, have overlapping spectra over a range of excitation. Time-resolved spectroscopy has been used to separate the emission bands. Both bands are excited in the region of the fundamental absorption edge, whereas in the area of transparency expressed no peaks. Presumably, both bands could be associated with intrinsic centers of different nature. The very weak luminescence of langasite with a maximum at 400 nm was registered only at T = 10 K. To the best of our knowledge it is the first observation of luminescence in langasite.