YVO4 Research Articles

Low-Temperature Synthesis of YVO4Nanoparticles and their Photocatalytic Activity

Yttrium orthovanadate (YVO4) nanoparticles with nearly spherical shape were successfully synthesized via a molten salt method at a low temperature of 200°C. The as-prepared powders were characterized by X-ray diffraction, transmission electron microscopy and UV-Vis spectroscopy, respectively. The results show that increasing salt amount and/or elevating calcining temperature can greatly promote the crystallization and growth of YVO4 phase. UV-Vis absorption spectra suggested that YVO4 nanoparticles with the smaller particle size have the stronger UV absorption, and the sequent photocatalytic degradation data also confirmed their higher photocatalytic activity.

Influence of sodium dodecyl sulfonate (SDS) on the hydrothermal synthesis of YVO 4:Eu 3+ crystals in a wide pH range

In this work, a facile hydrothermal route has been proposed for the morphology-controllable preparation of Eu-doped yttrium orthovanadate (YVO 4:Eu 3+) powders in the presence of sodium dodecyl sulfonate (SDS) as a template in a wide pH range. The structure, composition, morphology, and optical properties of the final products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL), respectively. It was found that single phase YVO 4:Eu 3+ micro- and nanocrystals with different shapes can be fabricated at 180 °C for 24 h with suitable amount of SDS in a wide pH range. The formation mechanism and the influence of SDS on the morphology of YVO 4:Eu 3+ micro- and nanocrystals were investigated as a function of pH value. The PL measurement revealed that the samples with different morphologies exhibited different values for optical properties, especially soybean-like nanopowders showed a higher intensity compared to other samples with different morphologies due mainly to their high packing densities and low scattering of light.

Ab initio vibrational and dielectric properties of [formula omitted

For the yttrium orthovanadate Y V O 4 with a tetragonal zircon-type structure, the first complete set of Raman-active and IR-active phonon modes has been calculated using ab initio density functional perturbation theory. The calculated IR reflectivity spectra are in good agreement with available experimental data. We report the calculated frequencies of three Raman-active modes that could not be detected experimentally and a new assignment of the experimental Raman data. The contributions of each IR-active phonon modes to static dielectric tensor have been determined.

A facile route to synthesize luminescent YVO4:Eu3+ porous nanoplates

Abstract Porous nanoplates made of yttrium orthovanadate doped with europeum (YVO 4 :Eu 3+ ) have been successfully synthesized via a chemical co-precipitation method using NH 4 VO 3 , Y 2 O 3 , Eu 2 O 3 and ethylene glycol. To investigate the effect of temperature on the pore size and morphology of the final product, the as-synthesized YVO 4 :Eu 3+ nanoplates were subjected to heat treatment at 300 and 600 °C for 2 h. The obtained samples were characterized by X-ray diffractometion, Fourier-transform infrared spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy and photoluminescence spectroscopy. The experimental results showed that the luminescent properties were significantly enhanced with increasing pore size of the YVO 4 :Eu 3+ porous nanoplates.

Electron Magnetic Resonance Investigation of Gadolinium Diffusion in Ceria Powders

The electron magnetic resonance (EMR) technique was used to investigate the diffusion of gadolinium in ceria (CeO2) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323, and 1373 K. The activation temperature for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be EA=485±5 kJ/mol. This value is very close to the one obtained for the diffusion of gadolinium in an oxide with a similar crystal structure, UO2, using the secondary ion mass spectrometry technique, EA=492 kJ/mol. On the other hand, it is much larger than the one obtained for the diffusion of gadolinium in yttrium vanadate (YVO4), EA=177 kJ/mol, a compound with a different crystal structure.

Luminescent oxide nanoparticles with enhanced optical properties

Yttrium vanadate particles doped with europium are studied for their applications as biomolecule labels. Two parts of our recent work are presented. The first concerns the thermal treatment of particles incorporated in a solid matrix. After annealing at 1000 °C and redispersion in water by dissolution of the matrix, the structural and optical properties are greatly improved without any modification of size; the obtained nanoparticles appear as perfect single crystals of 39 nm and have the same emission properties as the bulk material. Their quantum yield is worth 39% for 5% europium doping and the emission lifetime is 1 ms. The second aspect concerns the functionalization of the nanoparticles by the sol–gel condensation of aminopropyltriethoxysilane at the surface of particles. The chemical accessibility of amino groups grafted on the particles is measured by reaction with an organic fluorescent tag fluorescein isothiocyanate (FITC). These amine-coated nanoparticles were coupled to a peptidic toxin via a cross linker and allowed observation of the toxin motion bound to its membrane receptor.

Hydrothermal synthesis of well-dispersed YVO 4:Eu 3+ microspheres and their photoluminescence properties

Spherical-shaped Eu-doped yttrium orthovanadate (YVO 4:Eu 3+) powders were fabricated via disodium ethylenediamine tetraacetate (Na 2EDTA)-assisted hydrothermal technique. The as-synthesized YVO 4:Eu 3+ microspheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The experimental results showed that the morphology and size of the microspheres had a strong dependence on the concentration of Na 2EDTA and the reaction time of hydrothermal treatment. Spherical YVO 4:Eu 3+ crystals with the diameter of 1.0–3.0 μm were obtained in the presence of 0.025 M Na 2EDTA at 180 °C for 24 h. The photoluminescence measurement revealed that YVO 4:Eu 3+ powders with well-spherical shape have better red luminescence properties among all the samples.

Optically induced spin disorder in YVO3

Yttrium vanadate (YVO3) is an interesting material for studying optically induced phase transitions because it exhibits a rich variety of coupled structural and correlated electronic phases. We show that optical excitation effectively decouples spin and magnetic order and results in rapid spin melting within 4 ps while orbital order survives for longer than 100 ps.

紧凑型激光二极管端面抽运Nd∶YVO4内腔三倍频355 nm紫外激光器

紧凑型激光二极管端面抽运Nd∶YVO4内腔三倍频355 nm紫外激光器

Na 2EDTA-assisted hydrothermal synthesis and luminescent properties of YVO 4:Eu 3+ with different morphologies in a wide pH range

Nano- and micro-scaled Eu-doped yttrium orthovanadate (YVO 4:Eu 3+) powders had been fabricated via disodium ethylenediamine tetraacetate (Na 2EDTA)-assisted morphology controllable hydrothermal method in a wide pH range at 180 °C for 24 h. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The results showed that the pH value of the synthesis solution played a key role in the formation of the final products with different morphologies, including ball-like micro-spheres, micro-spheres composed of submicron cubes and flower-like structures containing nano-plates. The photoluminescence measurement revealed that the luminescent properties of the samples were changed by varying their morphologies. The significant ball-like micro-spheres of YVO 4:Eu 3+ particles had been synthesized, and the luminescence intensity of them is the strongest one among all products.

Influence of doping on thermal diffusivity of single crystals used in photonics: measurements based on thermal wave methods

Three crystals used in solid-state lasers, namely, yttrium aluminum garnet (YAG), yttrium orthovanadate (YVO(4)), and gadolinium calcium oxoborate (GdCOB), were investigated to determine the influence of dopants on their thermal diffusivity. The thermal diffusivity was measured by thermal wave method with a signal detection based on mirage effect. The YAG crystals were doped with Yb or V, the YVO(4) with Nd or Ca and Tm, and the GdCOB crystals contained Nd or Yb. In all cases, the doping caused a decrease in thermal diffusivity. The analysis of complementary measurements of ultrasound velocity changes caused by dopants leads to the conclusion that impurities create phonon scattering centers. This additional scattering reduces the phonon mean free path and accordingly results in the decrease of the thermal diffusivity of the crystal. The influence of doping on lattice parameters was investigated, additionally.

Preparation and characterization of tunable YVO 4: Bi 3+, Sm 3+ phosphors

Yttrium vanadate phosphors co-doped with Bi 3+- and Sm 3+ ions have been prepared via the solid-state reaction as well as via the sol–gel method. The luminescence studies demonstrate the potential of the prepared phosphors as multi-color emitters, which can be achieved by adjusting the excitation wavelengths. The excitation spectra of Bi 3+- and Sm 3+ co-doped phosphors clearly revealed energy transfer from Bi 3+ to Sm 3+ ions. When the co-doped phosphors were excited at 254 nm, the emission from Bi 3+ was dominant. Upon excitation at 365 nm, the emission from both Bi 3+ and Sm 3+ was detected. With 410 nm excitation, Sm 3+ ions were selectively excited to yield intense red emission. It is shown that the prepared phosphors with optimal concentrations of Bi 3+ and Sm 3+ can be excited at 254, 365 and 410 nm to yield yellow, orange and red emissions, respectively.

1.4-MHz repetition rate electro-optic Q-switched Nd:YVO_4 laser

An electro-optic (EO) deflector was used for Q-switching of a laser cavity with a Nd-doped yttrium vanadate (Nd:YVO(4)), enabling a short pulse width and a high peak power to be achieved at a high repetition rate of over 1 MHz. The EO deflector has a low optical loss during Q-switching without polarizers and can be used to form a short laser cavity. A repetition rate of 1.4 MHz with a pulse width of 39 ns was achieved. An output power of 2.7 W was obtained at a pump power of 6.5 W.

Prismatic imaging polarimeter calibration for the infrared spectral region

The calibration of a complete Stokes birefringent prismatic imaging polarimeter (BPIP) in the MWIR is demonstrated. The BPIP technique, originally developed by K. Oka, is implemented with a set of four Yttrium Vanadate (YVO(4)) crystal prisms. A mathematical model for the polarimeter is presented in which diattenuation due to Fresnel effects and dichroism in the crystal are included. An improved polarimetric calibration technique is introduced to remove the diattenuation effects, along with the relative radiometric calibration required for the BPIP operating with a thermal background and large detector offsets. Data demonstrating emission polarization are presented from various blackbodies, which are compared to data from our Fourier transform infrared spectropolarimeter.

Investigation of neodymium-diffused yttrium vanadate waveguides by confocal microluminescence

We report on the confocal microspectroscopic characterization of planar optical waveguides fabricated in yttrium vanadate (YVO4) crystals by thermal diffusion of neodymium ions. We have found that the waveguide formation is accompanied by Nd3+ fluorescence quenching and by a redshift of the Nd3+ sub-Stark transitions. These effects have been explained in terms of the high Nd3+ concentrations achieved close to the diffusion surface, which lead to the appearance of nonradiative processes, as well as to a local compression in the surroundings of the indiffused Nd3+ ions. By comparing with previous works, we have estimated an equivalent residual stress of 0.1 GPa. The possible mechanisms at the origin of waveguide formation have been also discussed.

Preparation and Luminescent Properties of YVO4:Eu3+ Nanofibers by Electrospinning

This paper describes a procedure based on electrospinning for generating europium-doped yttrium vanadate (YVO4:Eu3+) nanofibers with diameters ranging from 30 to 50 nm. The YVO4:Eu3+ nanofibers were obtained through calcining precursory nanofibers, which were prepared through the electrospinning method. Suitable electrospinning parameters, such as concentration of PVP in solution, spinneret tip-to-collector plate distance (TCD), and applied voltage between spinneret and collector plate, are used to obtain thinner and more uniform precursory nanofibers of YVO4:Eu3+, which is important for preparing smaller diameter pure YVO4:Eu3+ nanofibers. The luminescent properties of the YVO4:Eu3+ nanofibers including excitation and emission spectra and fluorescence lifetime were studied. The excitation spectrum shows a broad band extending from 200 to 350 nm, which corresponds to the strong vanadate absorption in YVO4:Eu3+. The emission spectrum is dominated by the red 5D0 --> 7F2 hypersensitive transition of Eu3+. The fluorescence lifetime of Eu3+ 5D0 --> 7F2 (619 nm) is determined to be 493 micros at room temperature, which is basically in accordance with that in the bulk (521 micros).

Influence of impurities and thermal treatment on spectroscopic properties and laser performance of thulium-doped yttrium vanadate crystals

Influence of impurities and thermal treatment on spectroscopic properties and laser performance of thulium-doped yttrium vanadate crystals was examined. YVO4 crystals nominally pure, single doped with Tm3+ and co-doped with Tm3+ and Ca2+ were grown by the Czochralski method and then thermally treated at 1150 °C for several hours in a reducing atmosphere (vacuum) or oxidizing atmosphere (air). Samples of crystals were investigated by nuclear magnetic resonance spectroscopy (NMR) and by optical spectroscopy methods. Laser performance of samples was examined upon laser diode pumping. For pure YVO4 and for YVO4 containing 0.5 at. % of Tm a single-site NMR spectrum of 51V nuclei was observed with central line widths of 2.5 and 3.2 kHz (FWHM), respectively. For samples containing 5 at. % of Tm the NMR spectrum was a superposition of multi-site spectra indicating at least three kinds of vanadium sites with axial symmetry. Optical absorption spectra did not contain bands that could be ascribed to V4+ ions in tetragonal sites. Level of matrix absorption in the visible region and its increase with decreasing wavelength from about 600 to 370 nm was found to be substantially dependent on conditions of thermal treatment. Thermal treatment of crystals and additional doping with Ca did not influence the 3 F 4 lifetime of thulium and laser performance of crystals, however. Infrared absorption spectra revealed OH- contamination in all samples. It has been concluded that the quenching of the 3 F 4 emission in samples containing 5 at. % of thulium is related to migration-accelerated energy transfer to hydroxyl ions acting as energy sinks.

Passive Q-switching of a diode-side-pumped Nd-doped mixed gadolinium yttrium vanadate bounce laser

High power passive Q-switching was achieved with a pulse width of 18–32 ns by using a diode-side-pumped Nd:Gd0.6Y0.4VO4 bounce amplifier. An average output power of > 8 W was obtained at a pump power of 39 W. The peak power of the Q-switched output was adjusted within 1.9–5.2 kW by changing the Nd concentration. The mixed vanadates showed significantly higher Q-switching performances in comparison with pure Nd:GdVO4.

Laser dazzling of infrared focal plane array cameras

Modern weapons systems often use infrared imaging for acquisition and tracking of targets. In the acquisition phase, the operator uses the system to detect the target and aim the weapon. In the tracking phase, the images from the camera are used to guide the weapon to the target. One possible method of protection against such imaging systems is laser dazzling. The intended effect is to deny the imager a clear view of the target by saturating the detector and consequently preventing the weapon from making a hit. The problem of locating the threat and pointing the laser at it is closely connected to the countermeasure effectiveness. This has been investigated particularly for specific applications such as directed infrared countermeasure (DIRCM) systems for aircraft self-protection. Another application is sniper detection, which uses the ‘cat’s-eye’ or retro-reflection effect, which occurs when a searching laser beam is directed at the visor of the rifle. We currently aim to use the retro-reflection effect in a wider range of applications for locating optics.1 The aim of our dazzling work is to quantify the effects of laser countermeasures on mid-wave infrared (MWIR) imaging to predict the decrease in the detection and pointing capabilities of weapons systems. Dazzling with a continuous or quasicontinuous pulsed laser causes a reversible saturation effect on the detector array. Most of the current MWIR lasers provide output power levels that do not exceed saturation levels for practical applications. Permanent damage effects require much higher irradiance levels at the camera front optics. This might be within reach at shorter ranges with these lasers, but is not addressed in our current research. In our experiments we used a periodically poled lithium niobate optical parametric oscillator (PPLN OPO) laser pumped by an Nd:YVO4 (yttrium orthovanadate) laser to generate a 3.9μm laser wavelength.2 Figure 1 presents images of a standard 256×320 indium antimonide (InSb) camera irradiated by Figure 1. Impact of increasing laser irradiance on the InSb camera image.

Determination of the thermal diffusivity of pure and doped yttrium orthovanadate by Ångström's method

Thermal diffusivities of pure YVO4 single crystal and single crystals doped with Nd, Tm and Ca ions are measured using a modified Angstrom's method. Measurements were carried out for main crystallographic directions ([100], [010] and [001]). Obtained results show that the thermal diffusivity in [001] direction is considerably higher than in (001) plane. Decrease of the thermal diffusivity is observed with growing concentration of dopants. For the heavier doped sample (5% at. of Tm + 0.4% at. of Ca) a drop of the thermal diffusivity is about 35%.