Luminescent Spectroscopy of the Yb3+^{3+} Ions in the PbWO4_4 Crystal

Luminescent properties of the PbWO$_4$ crystals undoped and doped with the Yb$^{3+}$ ions were studied. Emission spectra of the crystals consist of broadband matrix emission in 350–750 nm spectral range and narrow spectral lines caused by inner electron transitions in the impurity Yb$^{3+}$ ions in 920–1040 nm spectral range. Analysisof the linear spectra has shown that Yb$^{3+}$ ions form two types of emission centres. Structures of these centers are discussed taking into account possibility of the impurity ions incorporation in different positions (Pb and W sites) in the crystal lattice. Effects of the Yb$^{3+}$ impurities on matrix emission were studied. Transfer of excitation energy from matrix to the Yb$^{3+}$ decreases intensity of the red band of matrix emission. The Yb$^{3+}$ impurities also increase intensity of the blue band by formation of additional Yb$^{3+}$-induced channel of excitation of this band. The described effects of Yb$^{3+}$ doping on properties of matrix emission are caused by the Yb$^{3+}$ ions arranged inPb positions

Temperature behavior of matrix and impurity emission of La<inf>1&#x2212;x</inf>Eu<inf>x</inf>VO<inf>4</inf> powders synthesized by co-precipitation method

The La$_{1-x}$Eu$_x$VO$_4$ powders were synthesized by co-precipitation method. Luminescence spectra of the investigated samples consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the impurity Eu3+ ions. The both types of emission were studied within 10 - 300 K temperature range. Obtained dependencies are discussed using proposed models for matrix emission and structure of the nearest surrounding of the Eu$_{3+}$ centers