Transition Of Tm Research Articles

Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO₂ fiber.

Visible light thermal radiation from SiO2 glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO2 fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO2 fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO2 fibers are smaller than those from SiO2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO2 are potentially applicable for the fiber-optic thermometry above 900 K.

Near-infrared quantum-cutting luminescence and energy transfer properties of Ca3(PO4)2:Tm3+,Ce3+ phosphors

The phosphors Ca3(PO4)2:Tm3+ by co-doping Ce3+ have been synthesized by conventional high-temperature solid-state reaction method. Their spectroscopic properties in the UV-VIS-NIR range have been investigated. The first 5d crystal field level location and stokes shift have been determined from the UV excitation and emission spectra of Ca3(PO4)2:Ce3+. The three-photon NIR quantum-cutting luminescence of Tm3+ assigned to the electronic transitions of 1G4→3H4, 3H4→3F4 and 3F4→3H6 is observed, whether in Ca3(PO4)2:Tm3+ or Ca3(PO4)2:Tm3+,Ce3+. The energy transfer from Ce3+ to Tm3+ takes place with energy-transfer efficiency up to 34.5% for the Ca3(PO4)2:Tm3+,Ce3+. A cross relaxation scheme using the 5d states of Ce3+ and f-f transition of Tm3+ is proposed. The mechanism is revealed from energy level and decay measurements. The results show that the broadband absorption of Ce3+ sensitizer not only extends the spectrum conversion in UV region but also greatly enhances the photoluminescence intensities of the three-photon quantum cutting luminescence of Tm3+ doped Ca3(PO4)2.

Fiber-optic thermometry using thermal radiation from Tm end doped SiO2 fiber sensor.

Fiber-optic thermometry based on temperature dependence of thermal radiation from Tm(3+) ions was studied using Tm end doped SiO2 fiber sensor. Visible light radiation peaks due to f-f transition of Tm(3+) ion were clearly observed at λ = 690 and 790 nm from Tm end doped SiO2 fibers sensor at the temperature above 600 °C. Thermal radiation peaks are assigned with f-f transition of Tm(3+) ion, (1)D2-(3)H6, and (1)G4-(3)H6. Peak intensity of thermal radiation from Tm(3+) ion increases with temperature. Intensity ratio of thermal radiation peaks at λ = 690 nm against that at λ = 790 nm, I790/690, is suitable for the temperature measurement above 750 °C. Two-dimensional temperature distribution in a flame is successfully evaluated by Tm end doped SiO2 fiber sensor.

Luminescence Behavior of Tm<sup>3+</sup> Activated GdAlO<sub>3</sub> Phosphors Synthesized Using Solid-Reaction Method

Trivalent thulium ions (Tm3+) doped GdAlO3 (Gd1-xTmxAlO3) phosphors which show a blue luminescence of high color purity have been synthesized by using solid-state reaction method starting from nanosized powders. X-ray diffraction (XRD) measurements were used to analyze the phase transformations that take place during the preparation of the phosphors. The morphologies of the powders calcined at different temperatures were studied by using scanning electron microscopy (SEM). The luminescence properties of the compounds were investigated. Pure phase of orthorhombic type GdAlO3 (GAP) was yielded by calcining the phosphors at 1200°C for 8 h. The PL spectra showed representative Tm3+ emission. The strong band centered at ~488 nm and the weak one centered at 697 nm were attributed to the 1D2-3F4 and 1G4-3F4 transitions of Tm3+, respectively. The quenching concentration of Tm3+ was estimated to be ~0.75at.% (x=0.0075), for which can be ascribed to the exchange interactions. The decay curve was fitted to be a single exponent and the estimated fluorescent lifetime of the GdAlO3:Tm3+ phosphor was 1.73±0.08 ms.

Upconversion luminescence of Er3+, Tm3+ and Yb3+Co-doped Gd3Ga5O12 nanocrystals

A series of Er3+, Tm3+ and Yb3+ doped Gd3Ga5O12 nanocrystals were prepared by a combustion method. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and upconversion (UC) emission spectra were used to characterize the samples. The results of XRD indicate that Gd3Ga5O12: Er3+, Tm3+, Yb3+ nanocrystals with cubic phase can be obtained. Under the excitation of a 980 nm laser, the different rare earth ions doped Gd3Ga5O12 nanocrystals show upconversion luminescence involving the green emission attributed to the 2H11/2→4I15/2, 4S3/2→4I15/2 transitions of Er3+ ions, respectively, the red emissions assigned to the 4F9/2→4I15/2 transitions of Er3+ ions and the 1G4→3F4 as well as 3F2,3→3H6 transitions of Tm3+ ions, respectively, the blue emission attributed to 1G4→3H6 transitions of Tm3+ ions, and the near-infrared assigned to the 3H4→3H6 transitions of Tm3+ ions. The CIE coordinates for the samples are calculated. The dependence of their upconversion luminescence properties on Yb3+ ion concentration is investigated.

Highly sensitive optical thermometry based on upconversion emissions in Tm^3+/Yb^3+ codoped LiNbO_3 single crystal

Under 980 nm excitation, upconversion emissions originating from 3F(2,3)→3H(6) and 3H(4)→3H(6) transitions of Tm3+ ion in LiNbO3 single crystal were studied as a function of temperature in the range of 323-773 K. The 3F(2,3) and 3H(4) levels of Tm3+ ion are confirmed to be thermally coupled levels. By using fluorescence intensity ratio technique, the sensitivity of optical temperature sensor achieved in our work is higher than other reported temperature sensors. Additionally, this optical temperature sensor is well suited to high operating temperature. Tm3+/Yb3+ codoped LiNbO3 is a promising candidate for fabricating excellent optical temperature sensors.

Tunable white-light emission in single-phase Ca_9Gd(VO_4)_7:Tm^3+, Eu^3+

A series of Tm3+ and/or Eu3+ doped Ca9Gd(VO4)7 single composition phosphors were synthesized by a solid state reaction method, and their luminescence properties were investigated. Tm3+ and Eu3+ co-doped Ca9Gd(VO4)7 phosphors showed a blue with the peak at 477 nm and red with the stronger peak at 620 nm dual emission bands under the UV excitation, which originates from the f-f transitions of Tm3+ and Eu3+ ions, respectively. The energy transfer from O2--V5+ CT (charge transfer) energy to Tm3+ and Eu3+ ions as well as the energy transfer from Tm3+ to Eu3+ ions were investigated. The photoluminescence intensity ratio of blue and red emission could be tuned by adjusting the concentration of Tm3+ and Eu3+ ions and as a result the emission color varies from blue to white to red. The white-light emission is realized in single phased phosphor of Ca9Gd(VO4)7:Tm3+, Eu3+ by combining the Tm3+-emission and the Eu3+-emission.

Preparation and luminescence characteristics of LiYF4: Tm3+/Dy3+ single crystals for white-light LEDs

Tm3+ /Dy3+ co-doped LiYF4 single crystals were synthesized by using vertical Bridgman method in sealed Pt crucibles. When excited by a proper UV-light, the crystals show blue emission band centered at 485 nm, which overlaps between the transition of Tm3+ (1G4 → 3H6) and Dy3+ (4F9/2 → 6H15/2) ions, and yellow band of 573 nm ascribed to Dy3+ (4F9/2 → 6H13/2) ions. Both chromaticity coordinates and photoluminescence intensity vary with the excitation wavelengths and the concentration of rare earth dopants. A white light can be achieved from Tm3+ (0.6 mol%), Dy3+ (2.25 mol%) co-doped LiYF4 crystal with chromaticity coordinates of x ≈ 0.2836, y ≈ 0.3229, and color temperature T c = 8419 K by the excitation of a 350 nm light. It indicates that this crystal can be a potential candidate for the UV-light excited white-light emitting diodes.

White upconverted luminescence of Ho3+/Yb3+/Tm3+ tri-doped Gd2Mo3O9 phosphors

Abstract Yb 3+ /Tm 3+ /Ho 3+ tri-doped Gd 2 Mo 3 O 9 phosphors were synthesized by the high-temperature solid-state method. Under 980 nm near-infrared excitation, the white-light emission can be observed, which is consists of the blue, green, and red UC emissions. The green and red emission at 547 nm and 660 nm originated from the transition of Ho 3+ ( 5 S 2 , 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 ) and the blue emission at 475 nm attributed to the transition of Tm 3+ ( 5 G 4 → 5 H 6 ). In this experiment, we selected the optimum concentration ratio of the three rare earths for the bright white emission. The Commission internationale de L’Eclairage (CIE) coordinates for the samples were calculated, and chromaticity coordinates were very close to white light regions. We find that the calculated CIE color coordinates of the Yb 3+ /Tm 3+ /Ho 3+ tri-doped Gd 2 Mo 3 O 9 phosphors changed with the incident pump power from 400 mW/cm 2 to 1000 mW/cm 2 . The upconversion luminescence mechanism of the samples was discussed on its spectral. The white light may be proved to be a candidate material for applications in various fields.

Distribution, damage, and blue luminescence of Tm ion implanted into KTiOAsO4 crystal

Potassium titanyl arsenate (KTiOAsO4 or KTA) crystal was ion implanted by 500keV Tm+ ions with a fluence of 5.5×1014ions/cm2 at room temperature. The depth profile of implanted Tm+ ions into KTiOAsO4 crystal was measured by Rutherford backscattering spectrometry and calculated by the stopping and ranges of ions in matter (SRIM'2006) computer code. The results of SRIM'2006 calculation and X-ray diffraction analysis show that the surface of KTA crystal was almost amorphous state due to the Tm+ ion implantation. The excitation and emission spectrum of Tm implanted KTA at room temperature were measured. The visible emission spectrum consists of a main contribution in the blue region at 467nm corresponding to the Tm transition from the 1D2 to the 3F4 ground state.

Spectroscopic studies of Tm‐doped zirconia nanoparticles

AbstractIntra‐4f12 transitions of Tm3+ ions in zirconia powders processed by solution combustion synthesis (CS) were studied by optical techniques. The results were compared with the ones obtained in reference samples of yttria stabilized zirconia fibers grown by laser floating zone. The spectroscopic features observed for the tetragonal fibre were compared with the Stark lines detected in the polyphasic (monoclinic and tetragonal) powder suggesting additional Tm3+ sites/environments due to the ions in the monoclinic host. The stability of the blue 1D2 → 3F4 and red 1G4 → 3H6 transitions was found to be strongly dependent on temperature. For the fibres, the blue luminescence increases by a factor of two between 15 K and the room temperature when pumping the sample in the 1D2 level. When the excitation is performed in the 1G4 state a higher stability of the red luminescence was found to occur in fibres than in the polyphasic powder. Constant 1G4 → 3H6 integrated intensity was observed in the fibres, while a decrease of the red luminescence efficiency occurs with temperature for the polyphasic powder. The suppression of the nonradiative paths which compete with the radiative transition could be attained by using thulium doped yttria stabilized CS powders.

Growth and scintillation properties of (Lu1 − Tm )2SiO5 [x = 0.001, 0.01, 0.1, 1

(Lu 1 − x Tm x ) 2 SiO 5 ( x = 0.001, 0.01, 0.1, 1) single crystalline scintillators were grown by the μ-PD method. In transmittance measurement, absorption bands due to Tm 3+ 4f–4f transitions were observed at 260, 292, 356, 463, 680 and 790 nm and they could be ascribed to the transition from the 3 H 6 ground state to its excited states, 1 I 6 , 3 P 6 , 1 D 2 , 1 G 4 , 3 F 3 and 3 H 4 , respectively. Strong emission peak due to 1 D 2 → 3 F 4 transition of Tm 3+ was shown at 453 nm under X-ray irradiation. Photoluminescence decay time constant caused by this transition were evaluated to be 11.9 μs. Tm 1% doped one exhibited the highest light yield of 3530 ± 200 photons/MeV when excited by 137 Cs gamma-ray exposure. ► (Lu 1 − x Tm x ) 2 SiO 5 single crystals were grown by the μ-PD method. ► The Tm 3+ 4f–4f emission and absorption lines were observed. ► The scintillation decay times were evaluated as 11.9–13.5 μs. ► Pulse height measurements showed the 1% Tm sample had the highest light yield. ► Quenching was observed in higher Tm concentration.

Structure and luminescence properties of the novel multifunctional K2Y(WO4)(PO4):Ln3+ (Ln = Tb, Eu, Yb, Er, Tm and Ho) phosphors

Lanthanide ion (Tb, Eu, Yb, Tm, Er, and Ho) activated multifunctional phosphors K2Y(WO4)(PO4), (KYWP) were prepared via a conventional solid-state reaction. The crystal structure of KYWP as a new host matrix for luminescence was firstly defined to be the orthorhombic system with space group Ibca (73) via Rietveld refinement of the powder X-ray diffraction and the GSAS software. The vacuum ultraviolet (VUV) excited photoluminescence and cathodoluminescence (CL) analysis of individual Tb3+/Eu3+ activated KYWP phosphors exhibit excellent emission properties in their respective regions. Both KYWP:Tb3+ and KYWP:Eu3+ had high quenching concentration under 147 nm excitation attributed to a long Y–Y distance in KYWP structure, whereas they showed very low quenching concentration under low-voltage electron-beam excitation. This phenomenon was ascribed to the different mechanisms between CL and VUV excited luminescence. Under 980 nm laser excitation, yellow, purple, and red up-conversion (UC) emissions had been achieved in Yb3+–Er3+, Yb3+–Tm3+, and Yb3+–Ho3+ co-doped KYWP, respectively. In Yb3+–Tm3+–Ho3+ tridoped KYWP, red emissions emerging from transitions of Tm3+ changed to the transitions of Ho3+. And the possible reason had been elucidated by a cross-relaxation process between Tm3+ and Ho3+. Laser power dependence of the UC emissions and the energy level diagrams were studied to understand the UC and cross-relaxation mechanisms. The obtained results indicated that the multifunctional lanthanide ion doped KYWP exhibited excellent VUV photoluminescence, CL and multicolor UC luminescence properties.

Color control and white upconversion luminescence of LaOF:Ln3+ (Ln = Yb, Er, Tm) nanocrystals prepared by the sol–gel Pechini method

A series of Yb(3+)-Er(3+) and Yb(3+)-Er(3+)-Tm(3+) codoped LaOF nanocrystals were synthesized via a modified sol-gel Pechini method. The phases and morphologies as well as the luminescence properties of the as-prepared samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and upconversion luminescence (UCL) spectra, respectively. Under 980 nm near infrared (NIR) excitation, the UCL properties and the corresponding luminescent colors of the samples could be precisely modulated by changing the annealing temperatures, the dopant concentrations and the pump densities. By regulating the intensities of blue, green and red emissions in Yb(3+)-Er(3+)-Tm(3+) codoped LaOF nanocrystals, an ideal white upconversion luminescence with chromaticity coordinates of (0.331, 0.368) is obtained in La0.885Yb0.1Er0.01Tm0.005OF nanocrystals for the first time. The blue, green and red components of the white light come from the (1)G4 → (3)H6 transition of Tm(3+), (2)H11/2/(4)S3/2 → (4)I15/2 transitions of Er(3+) and (4)F9/2 → (4)I15/2 transition of the Er(3+) ions, respectively. The possible physical mechanisms involved in the different upconversion processes were discussed in detail.

Evidence of non-coincidence of normalized sigmoidal curves of two different structural properties for two-state protein folding/unfolding

In practice, the observation of non-coincidence of normalized sigmoidal transition curves measured by two different structural properties constitutes a proof of existence of thermodynamically stable intermediate(s) on the folding ↔ unfolding pathway of a protein. Here we give first experimental evidence that this non-coincidence is also observed for a two-state protein denaturation. Proof of this evidence comes from our studies of denaturation of goat cytochrome-c (g-cyt-c) at pH 6.0. These studies involve differential scanning calorimetry (DSC) measurements in the absence of urea and measurements of urea-induced denaturation curves monitored by observing changes in absorbance at 405, 530, and 695nm and circular dichroism (CD) at 222, 405, and 416nm. DSC measurements showed that denaturation of the protein is a two-state process, for calorimetric and van’t Hoff enthalpy changes are, within experimental errors, identical. Normalization of urea-induced denaturation curves monitored by optical properties leads to noncoincident sigmoidal curves. Heat-induced transition of g-cyt-c in the presence of different urea concentrations was monitored by CD at 222nm and absorption at 405nm. It was observed that these two different structural probes gave not only identical values of Tm (transition temperature), ΔHm (change in enthalpy at Tm) and ΔCp (constant-pressure heat capacity change), but these thermodynamic parameters in the absence of urea are also in agreement with those obtained from DSC measurements.

Thermal strain and magnetization of the ferromagnetic shape memory alloy Ni52Mn25Ga23 in a magnetic field

The objective of this paper is the investigation of the correlations between crystal structure and the magnetization of Ni–Mn–Ga Heusler alloy. Thermal strain, permeability, and magnetization measurements of the ferromagnetic shape memory alloy Ni52Mn25Ga23 were performed across the martensite transition temperature TM and reverse martensite transition temperature TR at atmospheric pressure. When cooling from the austenite phase, thermal strain steeply decreases because of martensite transition. Permeability suddenly increases at the Curie temperature TC=358K, indicating ferromagnetism, and suddenly decreases to around TM=328K. This indicates that the lattice transformation and magnetic phase transition correspond to each other. The percentage of contraction by martensite transition at TM and in a magnetic field is twice that in zero fields. Considering with other Ni–Mn–Ga alloys, it is supposed that the magnetic field influences the orientation of the easy c-axis along the magnetic field, and then the variant rearrangement occurs, and consequently, the variation in the strain between zero fields and non-zero field is observed. The measurement results indicate that the regions above and below TM or TR are the ferromagnetic-austenite (Ferro-A) and ferromagnetic-martensite (Ferro-M) phases, respectively. Magnetic phase diagrams were constructed from the results of the temperature dependence of thermal strain. TM and TR increase gradually with magnetic field. TM shift in magnetic fields (B) around zero magnetic field was estimated as dTM/dB=0.46K/T, indicating that magnetization influences martensite transition and the dTM/dB value is the same as that of Ni52Mn12.5Fe12.5Ga23, thereby suggesting the Ferro-M to Ferro-A transition.

YAl3(BO3)4:Tm3+, Dy3+: A potential tunable single-phased white-emitting phosphors

Tm3+ and Dy3+ co-doped YAl3(BO3)4 phosphors were synthesized by the solid state reaction method. The phosphors show blue emission band centered at 450nm originated from the transition of Tm3+ ions and yellow band of 573nm ascribed to Dy3+ ions excited by UV light. The emission colors are tuned from blue to white and ultimately to yellow through concentration variation of luminescent centers of Tm3+ and Dy3+ in YAl3(BO3)4 phosphors. A white light can be achieved from YAl3(BO3)4:0.03Tm3+, 0.09Dy3+ phosphor with chromaticity coordinates of (0.310, 0.331) under excitation at 365nm. The results show that the single-phased YAl3(BO3)4:Tm3+, Dy3+ phosphors are a potential phosphors for current illuminated light source.

Diode-pumped 2 μm vibronic (Tm3+, Yb3+):KLu(WO4)2 laser

We report on laser operation in a (6 at. % Tm, 5 at. % Yb):KLu(WO4)2 codoped crystal. The vibrational frequencies of KLu(WO4)2 are coupled to the electronic transitions of Tm3+ at 1946 nm, creating virtual final laser levels at higher energy than the ground level 3H6 of Tm3+. The longest recorded laser wavelength was 2039 nm, which is longer than permitted by a pure electronic transition in Tm3+ ions in KLu(WO4)2. We show that every laser wavelength can be explained with the electron-phonon coupling effect, where the vibration frequencies were determined through Raman spectroscopy.

Upconversion Luminescent Properties of YVO<sub>4</sub>:Tm<sup>3+</sup>, Ho<sup>3+</sup>, Yb<sup>3+</sup>

YVO4 co-doped with Tm3+/Ho3+/Yb3+ were synthesized by the high temperature solid state method and the optical properties of phosphors were characterized. Intense visible emissions centered at around 475, 541 and 649 nm, originated from the transitions of Tm3+:1G4→3H6, Ho3:5S2/>:5F4 →5I8, Tm3+:5G4→3F4 and Ho3+:5F5→5I8, respectively, have been observed in samples upon excitation with a 980 nm laser diode, and the involved mechanisms have been explained.

Up-conversion processes of rare earth ions in heavy metal glasses

Heavy metal lead germanate glasses doubly doped with Yb3+ and Ln3+ ions (Ln=Er, Tm) were investigated. Up-conversion spectra of Er3+ and Tm3+ were registered under diode-laser excitation of Yb3+. Up-conversion luminescence bands corresponded to 4S3/2→4I15/2 (green) and 4F9/2→4I15/2 (red) transitions of Er3+ as well as 1G4→3H6 (blue) and 3H4→3H6 (NIR) transitions of Tm3+, respectively.