La Phosphate Research Articles

Construction of order mesoporous (Eu–La)/ZnO composite material and its luminescent characters

For the first time, the order mesoporous zinc oxide was synthesized by a soft template synthesis method. The Eu and La phosphate were introduced into the prepared mesoporous zinc oxide by the high temperature solid phase method, and got the mesoporous rare earth/zinc oxide composite materials. The luminescence characters of the materials were studied. The influences of La to Eu luminescent properties had been studied, and the optimum proportion of Eu and La was discussed. The influences of La and Eu to ZnO luminescence properties were also been studied. La phosphate had the large influence to Eu luminescent. ZnO had a strong emission peak at 469nm, which overlapped with the 7F0–5D2 transition excitation peak of Eu at 465nm. It indicated that the effective energy transfer happened between ZnO and Eu, which strongly enhanced the luminescence intensity of Eu. At the same time, the Eu and La phosphates could regulate the defect density of ZnO, which could regulate the luminescent intensity of ZnO, and realized the adjustment of luminescent color between green and red light.

The preparation of rare earth phosphate fine particles in an emulsion liquid membrane systemElectronic supplementary information (ESI) available: SEM images of phosphate particles prepared in the homogeneous system, and SEM images of La phosphate particles prepared via the ELM system, following calcination for 2 h at 573 and 1373 K. See http://www.rsc.org/suppdata/jm/b1/b105743j/

Phosphate particles of the selected rare earth metals have been prepared, using an emulsion liquid membrane [ELM, water-in-oil-in-water (W/O/W) emulsion] system, consisting of Span 83 (sorbitan sesquioleate) as surfactant and EHPNA (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) as extractant (cation carrier). The rare earth ions are extracted from the external water phase of the ELM system and are stripped into the internal water phase, containing phosphoric acid solution, to form the corresponding rare earth phosphate particles. The morphology and size of the particles are well-controlled by using the ELM system, and submicrometer-sized spherical phosphate particles are obtained, while micron-sized and irregular-shaped phosphate particles are obtained in homogeneous aqueous solutions. The resulting submicrometer-sized spherical particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and thermal analysis (TG–DTA). The characterization of La-based particles revealed that the fine particles obtained were of hexagonal structure, but their crystalline structure was changed to a monoclinic structure by calcination at 1373 K. Composite LaPO4:Ce3+,Tb3+ phosphor particles were then prepared by transporting La3+, Ce3+, and Tb3+ ions simultaneously, with the resulting particles showing good photoluminescence at 545 nm. In the ELM system, the size of the particles is able to be controlled in the range of 0.28 to 0.65 μm by changing the concentration of Span 83, whereas that in the homogeneous system is about 0.7 μm.

Optimization of the parameters of active elements of miniature lasers utilizing concentrated Li–Nd–La phosphate glass

A description is given of a method for selection of the diameter of an active element in a laser utilizing concentrated Li–Nd–La phosphate glass. It is shown that the diameter of the active element with a high neodymium concentration has to be small in the Q-switching regime when the output energy is fairly low. Numerical estimates are obtained of the dimensions of the active element and of the neodymium concentration necessary to achieve an output energy of 20 mJ. The results are given of an experimental investigation of a laser with a 2-mm-diameter active element made of concentrated Li–Nd–La phosphate glass operating under conditions of free running, active Q switching, and passive Q switching.

PassivelyQ-switched laser utilizing concentrated Li–Nd–La phosphate glass

An investigation was made of the efficiency of a laser utilizing a concentrated Li--Nd--La phosphate glass as the active medium and an LiF crystal with F/sup -//sub 2/ centers as a passive Q switch. The efficiency was about 0.5% in the pump energy range 5.6--13 J and the distribution of the output radiation corresponded to the TEM/sub 00/ mode. The main factor which limited the output energy of the laser pulses was the partial filling of the aperture of the glass active element. The experimental results were compared with calculations. Relationships were obtained for estimating (with an accuracy sufficient for practical purposes) the values of the parameters of the output pulses obtained under various experimental conditions. Estimates were obtained of the influence of the residual and induced absorption, and of the relaxation time of the passive switch on the lasing efficiency.

Use of high-concentration Li–Nd–La phosphate glass inQ-switched lasers

Results are presented of an experimental study of the use of high-concentration Li--Nd--La phosphate glass in Q-switched lasers for the giant-pulse and pulse-periodic regimes. When an electro-optic switch and a rotating prism were used for Q switching, a 1% efficiency was achieved. When a passive switch utilizing color centers in LiF was used, the laser efficiency was 0.5%. A method of optimizing a Q-switched laser for a given output energy is described.

Efficiency of an Li–Nd–La phosphate glass laser at low pump energies. Free lasing

An investigation was made of the free-lasing regime in a high-concentration Li–Nd–La phosphate glass pumped in the energy range 1–15 J. A laser efficiency of 2.9% was obtained for a pump energy of 14.5 J. Estimates were made of the intracavity losses and the maximum attainable efficiency was determined. An investigation was made of the laser performance in the giant pulse regime and at pulse repetition frequencies of up to 25 Hz.

Investigation of the laser characteristics of Li–Nd–La phosphate glass active elements

A comparative investigation was made of the laser characteristics of 5×50 mm active elements made of Li–Nd–La phosphate glass with an Nd3+ ion concentration of 8×1020 cm–3 and made of Y3Al5O12:Nd3+ with an Nd3+ ion concentration of 1.3×1020 cm–3. For Li–Nd–La phosphate glass active elements, the threshold pump energy was 1 J and the dynamic efficiency was 1.5 times higher than the maximum efficiency for Y3Al5O12:Nd3+. This gave a total laser efficiency of ~0.5% for a pump energy of 2 J and higher than 1% for a pump energy of 4 J. An investigation of the dependence of the pulse output energy on the average pump power for an Li–Nd–La phosphate glass active element showed that up to pump powers of ~250 W, the output energy did not change by more than 10%.

Investigation of nonradiative losses and pulse-periodic stimulated emission from Li–Nd–La phosphate glass

An investigation was made of the concentration dependences of the decay kinetics, nonradiative deactivation probability, and absolute quantum efficiency of the luminescence from the /sup 4/F/sub 3///sub 2/ upper laser level of Nd/sup 3 +/ in Li--Nd/sub x/--La/sub 1//sub - x/ phosphate glasses. The quenching of the luminescence from the /sup 4/F/sub 3///sub 2/ level of Nd/sup 3 +/ in these Li--Nd/sub x/--La/sub 1//sub - x/ phosphate glasses was much weaker than in the majority of the known laser matrices. A flashlamp-pumped sample of Li--Nd/sub 0//sub .//sub 2/--La/sub 0//sub .//sub 8/ emitted stimulated emission at a pulse repetition frequency up to 50 Hz.