Vesna Đorđević

Temperature luminescence properties of Eu3+-doped Gd2O3 phosphors

Rare earth (RE) oxides are important hosts for the luminescence of RE activators with numerous practical applications in light-emitting devices. In this work, we investigated the possibility for Gd2O3:Eu3+ usage in phosphor thermometry by observing the temperature changes of trivalent europium ion transitions from the 5D0 and 5D1 energy levels to the ground-state levels. A set of three samples of Eu3+-doped Gd2O3 (1, 5 and 10 at.% Eu3+) was produced via combustion synthesis. The sample crystalline structure is confirmed by XRD measurements. The intensity ratio of the two emission lines was studied as a function of temperature in the temperature range 300–800 K, and lifetime was measured in the interval 10–800 K. All three Gd2O3:Eu3+ samples proved to have good potential for the development of thermographic phosphors.

Thermographic properties of Sm3+-doped GdVO4 phosphor

Rare-earth orthovanadates are important hosts for the luminescence of rare earth activators with considerable practical applications in the artificial production of light. In this paper we investigated the possibility for GdVO4:Sm3+ usage in phosphor thermometry by observing the temperature changes of trivalent samarium transitions from 4F3/2 and 4G5/2 energy levels to the ground state. A set of three samples of Sm3+-doped GdVO4 (0.5, 1 and 2 mol.% Sm3+ with respect to Gd3+ ions) was produced via solid state synthesis. The sample crystalline structure is confirmed from x-ray diffraction (XRD) measurements. Photoluminescence measurements were recorded in the temperature range 293–823 K and the fluorescence intensity ratio of the paired emissions bands was studied as a function of temperature. All three GdVO4:Sm3+ samples proved to have good potential for the development of thermographic phosphors, whereas the maximum sensitivity of approximately 4.5×10-4 K−1 was found for the sample with 2 mol.% Sm3+ in the temperature region around 750 K.

MgTiO3:Mn4+ a multi-reading temperature nanoprobe

MgTiO3 nanoparticles doped with Mn4+, with homogeneous size ranging about 63.1 ± 9.8 nm, were synthesized by a molten salt assisted sol gel method. These nanoparticles have been investigated as optical thermal sensors. The luminescence of tetravalent manganese ion in octahedral environment within the perovskite host presents drastic variations with temperature. Three different thermometry approaches have been proposed and characterized. Two luminescence intensity ratios are studied. Firstly between the two R-lines of Mn4+ emission at low temperature (−250 °C and −90 °C) with a maximal sensitivity of 0.9% °C−1, but also secondly between 2E → 4A2 (R-line) and the 4T2 → 4A2 transitions. This allows studying the temperature variation within a larger temperature range (−200 °C to 50 °C) with a sensitivity between 0.6% °C−1 and 1.2% °C−1 over this range. The last proposed method is the study of the lifetime variation versus temperature. The effective lifetime value corresponds to a combination of transitions from two excited energy levels of the tetravalent manganese (2E and 4T2) in thermal equilibrium toward the fundamental 4A2 state. Since the more energetic transition (4T2 → 4A2) is spin-allowed, contrary to the 2E → 4A2 one, the lifetime drastically decreases with the increase in temperature leading to an impressive high sensitivity value of 4.1% °C−1 at 4 °C and an exceptional temperature resolution of 0.025 °C. According to their optical features, MgTiO3:Mn4+ nanoparticles are indeed suitable candidates for the luminescence temperature probes at the nanoscale over several temperature ranges.

Processing and characterization of up-converting Er3+ doped (Lu0.5Y0.5)2O3 nanophosphor

Abstract In this paper we demonstrate visible up-conversion emission of Er3+ doped (Lu0.5Y0.5)2O3 nanophosphor and discuss possible mechanisms for pumping the upper energy levels of Er3+ ions. Polymer complex solution synthesis yields well crystalline, pure-phase cubic nanopowder with particle size in the 20–50 nm range. Red, green and blue up-conversion emission is measured under near-infrared excitation (1 540 nm), over the temperature range 10–300 K. The red/green intensity ratio indicates that the mechanism responsible for populating red up-conversion is temperature dependent. Decay times are found to be around 0.25 ms for red and green, and around 70 μs for blue emission.

White- and blue-light-emitting dysprosium(III) and terbium(III)-doped gadolinium titanate phosphors

Here we report the synthesis and structural, morphological, and photoluminescence analysis of white- and blue-light-emitting Dy3+ - and Tm3+ -doped Gd2 Ti2 O7 nanophosphors. Single-phase cubic Gd2 Ti2 O7 nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy3+ -doped and ~50 nm for Tm3+ -doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy3+ -doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue-light excitation. Intense blue light was obtained for Tm3+ -doped Gd2 Ti2 O7 under UV excitation suggesting that this material could be used as a blue phosphor.