The dynamics of the photoluminescence of Pr3+ in mixed lanthanum yttrium oxyorthosilicate hosts

Praseodymium (Pr3+) doped mixed lanthanum yttrium oxyorthosilicate (LaYSiO5) powder phosphors were synthesized using urea-assisted combustion method. The molar ratio of La:Y were varied in the following manner: La2-xYxSiO5 (x= 0,0.5, 1, 1.5, 2), were x= 0 is pure La2SiO5, x= 2 is pure Y2SiO5 and x = 0.5, 1, and 1.5 are the admixtures of the two compounds. The X-ray diffractometer results showed that the La2SiO5 and Y2SiO5 crystalized in their pure monoclinic phases, while their admixtures are both present in the same phase. The Burstein Moss (BM) shift was used to explain the increase observed in the band gap after doping. The influence of the host crystal field on the branching ratios of the photoluminescence emission intensities of the P-3(0) and D-1(2) energy levels of Pr3+ were studied. The electronic transition from the P-3(0) transition dominated the emission spectra when x = 0, while the D-1(2) electronic transition dominated when x=2. The variation in the branching ratios of the P-3(0) and D-1(2) emission with the change in the molar ratio of La:Y could be due to P-3(0) -> D-1(2) non-radiative transitions, which increased with the crystal field of the host as the value of x increased (i.e., as the molar ratio of Y increases). Furthermore, it was shown that the P-3(0) emission lines emerged from Pr3+ ions occupying Lal and Y1 sites of La2SiO5 and Y2SiO5 respectively, while the D-1(2) emission lines emerged from Pr3+ ions occupying Lag and Y2 sites. The decay curve showed three lifetime components from both P-3(0) and D-1(2) emission lines, with the D-1(2) lines having higher lifetimes in all cases. 2017 Elsevier B.V. All rights reserved.