Luminescence properties of Pr3+ in titanates and vanadates: Towards a criterion to predict 3P0 emission quenching (original) (raw)

Red luminescence induced by intervalence charge transfer in Pr3+-doped compounds

Journal of Luminescence, 2007

The excited state dynamics of the Pr 3+ in oxide lattices is revisited in the light of the 'virtual recharge' model. The connection between the quenching of the blue-green emission from the 3 P 0 level and the formation of a Pr 3+ to metal intervalence charge-transfer state (IVCTS) is discussed on the basis of new experimental evidences. Updated information is presented, concerning the energy position of the IVCTS in various materials and its relation with the host properties. Finally, the limits of the proposed model are outlined and the perspectives for future work are pointed out. r

Making red emitting phosphors with Pr3+

Optical Materials, 2006

UV-excited red-emitting phosphors are obtained using Pr 3+ as the luminescent activator and host lattices containing closed-shell transition metal ions (especially titanates, vanadates and niobates). In these oxidant lattices, the quenching of the otherwise greenish-blue emitting 3 P 0 level is induced by a low-lying Pr-to-metal intervalence charge transfer state (IVCT). A simple criterion based on the optical electronegativities of the d 0 lattice cations (M n+ ) and average Pr 3+ À M n+ distances is proposed to predict 3 P 0 quenching in these lattices.

UV and Visible Luminescence of Pr3+ Doped Oxides: New Materials

MRS Proceedings, 2008

The garnet Ca3Sc2Si3O12 (CSSO) and the silico-carnotite Ca3Y2Si3O12 (CYSO) and Ca3Lu2Si3O12 (CLSO) materials, both undoped and doped with Pr3+, have been synthesized by solid state reaction at high temperature. The luminescence spectroscopy and the excited state dynamics of the materials have been studied upon VUV and X-ray excitation using synchrotron radiation. All doped samples have shown efficient 5d-4f emission upon direct VUV excitation of 5d levels, but only CSSO:Pr3+ shows luminescence upon interband VUV or X-ray excitation. The VUV excited emission spectra of CYSO:Pr3+ and CLSO:Pr3+ show features attributed to emission from two distinct sites accommodating the Pr3+ dopant. The decay kinetics of the Pr3+ 5d-4f emission in CSSO:Pr3+ upon VUV excitation across the conduction band are characterized by decay times in the range 25-28 ns with no significant rise after the excitation pulse. They appear to be faster upon X-ray irradiation than for VUV excitation. Weak afterglow comp...

The dynamics of the photoluminescence of Pr 3+ in mixed lanthanum yttrium oxyorthosilicate hosts

Sensors and Actuators B: Chemical, 2017

Praseodymium (Pr 3+) 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 3 P0 and 1 D2 energy levels of Pr 3+ were studied. The electronic transition from the 3 P0 transition dominated the emission spectra when x = 0, while the 1 D2 electronic transition dominated when x = 2. The variation in the branching ratios of the 3 P0 and 1 D2 emission with the change in the molar ratio of La:Y could be due to 3 P0→ 1 D2 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 3 P0 emission lines emerged from Pr 3+ ions occupying La1 and Y1 sites of La2SiO5 and Y2SiO5 respectively, while the 1 D2 emission lines emerged from Pr 3+ ions occupying La2 and Y2 sites. The decay curve showed three lifetime components from both 3 P0 and 1 D2 emission lines, with the 1 D2 lines having higher lifetimes in all cases.

Using a structural criterion for the selection of red-emitting oxide-based compounds containing Pr3+

Journal of Alloys and Compounds, 2004

In a number of oxide-based host lattices, the Pr 3+ ion exhibits a prominent red 1 D 2 → 3 H 4 emission instead of the usual greenish-blue luminescence from 3 P 0 level. Although different radiationless relaxation processes can contribute to the quenching of 3 P 0 emission in these compounds, all of them are more or less closely connected to the structural characteristics of the host networks. From structural and optical studies of several compounds containing Pr 3+ ions, we propose a very simple criterion, founded on the calculation of point charge electrostatic potentials involving both the first (O 2− ) and second (metallic cations) coordination environments around one given Pr 3+ site in the host structures, to predict either total or partial quenching of 3 P 0 luminescence.

Concentration effects on Pr3+ luminescence in LaAlO3 crystals

Optical Materials, 2011

Concentration dependant emission spectra and fluorescence dynamic profiles have been investigated in Pr x La 1Àx AlO 3 single crystals in order to better understand processes responsible for concentration quenching of the praseodymium 3 P 0 and 1 D 2 emissions. The cross-relaxation transfer rates were experimentally determined as a function of Pr 3+ concentration. Decays were modeled and nearest-neighbor trapping rates were calculated.

Luminescence Spectroscopy and Decay Kinetics of Pr3+ Ions in K3LuSi2O7:Pr3+

Physics of the Solid State, 2019

The luminescent characteristics of K 3 LuSi 2 O 7 :Pr 3+ (1%), which is a promising optical material for the use as a scintillator, have been studied using a set of techniques. The luminescence spectra of K 3 Lu-Si 2 O 7 :Pr 3+ (1%) contain two bands in the UV-range with peaks at 284 and 330 nm, which correspond intraconfigurational 5d → 4f transitions in the Pr 3+ ions. The radiation in the visible and near IR range (480-850 nm) has been represented by the intraconfigurational 4f → 4f transitions. The kinetics of 5d → 4f-luminescence contains a build-up stage (τ rise ∼ 7-12 ns), nonexponential decay stage (τ 1/2 ∼ 60 ns), and a slow component of the μs-range when excited by high-frequency (∼8 MHz) synchrotron radiation of the X-ray range. The fast component of the decay (τ = 54 ns) dominates in the decay kinetics of luminescence along with the build-up stage while the contribution of the μs decay component is less than 0.5% at the excitation by an pulse electron beam (5Hz). The excitation spectra of d-f-and f-f-photoluminescence in the ultraviolet and vacuum ultraviolet range that are measured using synchrotron radiation reveal features that are caused by both intracenter transitions and processes related to the energy transfer from the intrinsic electronic excitations to the impurity center.

07-B C. Jamalaiah et al. Journal of Luminescence 129 (2009) 1023–1028

Spectroscopic and laser properties of PbO-H 3 BO 3 -TiO 2 -AlF 3 glasses doped with 0.1, 0.5, 1.0 and 2.0 mol% of Pr 6 O 11 have been studied. Optical absorption spectra were recorded in the UV-vis-NIR regions and the observed absorption bands were assigned to different electronic transitions from 3 H 4 ground state of 4f 2 configuration. The three phenomenological Judd-Ofelt (J-O) parameters O t (t ¼ 2, 4, 6) were determined from the measured oscillator strengths by including as well as excluding the 3 H 4 -3 P 2 hypersensitive transition in J-O analysis. The emission characteristics such as stimulated emission cross-sections (s e ), measured branching ratios (b m ), measured lifetimes (t m ), quantum efficiencies (Z) and gain parameters (s e  t m ) have been evaluated for the principal intermanifold transitions of Pr 3+ from the 3 P 0 and 1 D 2 states to the lower lying manifolds in the visible region. From the emission and decay measurements, the effect of Pr 3+ ion concentration on the quenching of the 1 D 2 measured lifetimes has been discussed.

Emission properties of (SrTiO3–TiO2):Pr3+ eutectic with self-organized fractal microstructure

Optical Materials, 2011

An investigation of spectroscopic properties of (SrTiO 3-TiO 2):Pr 3+ eutectic and, for comparison, of bulk SrTiO 3 :Pr 3+ and TiO 2 :Pr 3+ crystals is presented. Luminescence spectra have been measured under both 450 nm and 350 nm excitation wavelength. For UV excitation they are characterized by a dominant red luminescence corresponding to transition from the 1 D 2 level of Pr 3+ ions. The mechanism responsible for quenching of blue (from 3 P 0 state) and intensification of red luminescence is proposed to be thermally-induced radiationless relaxation involving a low-lying Pr 3+-Ti 4+ intervalence charge transfer state. Measured decay constants of 1 D 2 excited state of Pr 3+ are compared with values obtained for other praseodymium doped titanate hosts.

What makes the luminescence of Pr3+different in CaTiO3 and CaZrO3 ?

Journal of Alloys and Compounds, 2004

Although orthorhombic CaZrO 3 and CaTiO 3 perovskites are characterised by very similar structural features, they show different luminescence properties when doped with Pr 3+ ions: the former exhibits the typical greenish-blue 3 P 0 → 3 H 4 emission, while the latter shows a single red 1 D 2 → 3 H 4 luminescence. The explanation of this difference requires to understand the mechanism responsible for total quenching of 3 P 0 emission in CaTiO 3 host. Among the different possible relaxation pathways from 3 P 0 to 1 D 2 , intersystem crossing through low lying 4f 1 5d 1 levels has been proposed in a previous study. Owing to new spectroscopic results on CaZrO 3 :Pr 3+ and CaTiO 3 :Pr 3+ , the role of the 4f5d band is reconsidered and an alternative relaxation channel is proposed via low lying intervalence charge transfer state.