Blue fluorescence of Ti3+ ions in Ti3+ - doped SrAl0.5Ta0.5O3:LaAlO3 crystals

Titanium - doped SrAl0.5Ta0.5O3:LaAlO3 crystals (SAT:LA) perovskite solid solution single crystals were grown by the Czochralski method for two Ti concentrations 1 wt.% (LSAR1) and 2 wt.% (LSAT2). It was stated that incorporation of Ti into SAT:LA crystal takes place in a non-uniform way. Ti3+ ions enter the crystal mainly in its conical part and mainly inside thin a (2-3 mm) layer within the crystal boundary. At room temperature, crystals from conical part of the boule reveal strong absorption created at about 529 nm for the case of LAST1 single crystal while at about 451 and 651 nm for the case of LAST2. Low temperature measurements have shown two absorption peaks centered at about 489 and 562 nm. Moreover, 850 nm peak is clearly observed. The intensity of the above described absorption coefficient strongly depends on the dopant concentration and reaches even 80 cm-1. The above bands seem to be connected with centers not emitting Ti3+. After γ-irradiation, additional absorption is observed, peaked at about 423 nm which gives two emission bands placed near 400 and 800 nm (375 nm excitation wavelength). They seem to be Ti3+ emissions coming from Ti3+ ions, occupying two different lattice octahedral positions one which is octahedral (Al, Ti) site. Blue fluorescence is self-evident. (author)