Xiuli Yan

Study of single-crystal growth of Tm3+: CaYAlO4 by the floating-zone method

Single crystals of heavily Tm3+-doped CaYAlO4 have been grown in various atmospheres by the floating-zone method for the first time. The optimal growth conditions have been obtained. Three major types of defects observed in the crystals are discussed in detail. The colors of crystals are found to relate to oxygen point defects. The optical absorption spectrum of crystals shows broad and intense absorption bands in the visible and the near-infrared regions. Excitation in the 804 nm band produces a broad and intense emission band with a peak near 1.8 mu m. The results show that Tm3+ : CaYAlO4 is a promising tunable solid-state laser material for 1.8 mu m laser operation using diode pumping without thermoelectronic regulation

Growth of Tm:Ho:YVO4 laser single crystals by the floating zone method

The growth of high optical quality Tm : Ho : YVO4 single laser crystals by the floating zone method is reported. The relationship between crystal quality and growth conditions was studied and the optimum method was obtained. The absorption and fluorescence spectra were measured at room temperature and the influence of concentration of Tm3+ and Ho3+ On the emissions is also discussed

Growth of laser single-crystals Er : YVO4 by floating zone method

Magnetization and resistivity of Pr1-xCaxMn1-yFeyO3 (x = 0.6, 0.7, 0.8; y = 0, 0.05, 0.1, and 0.15) manganites have been investigated between 77 and 350 K. The substitution of Mn with Fe does not affect markedly the lattice constants of the studied compounds, but suppresses strongly the charge ordering. These compounds show semiconductive behavior in the investigated temperature range independent of the Fe concentration. Increase of the Fe content leads to increasing magnetization at low temperatures, but none of the compositions shows a pronounced ferromagnetic component. We connect the observed behavior with the bi-strips model of charge ordering as developed for the Pr1-xCaxMnO3 compounds in the concentrational: range 0.3 less than or equal to x < 0.75

Growth of semiconducting Nd2CuO4 and as-grown superconductive Nd1.85Ce0.15Cuo4−δ single crystals

Nd2CuO4 and Nd(1.85)Ce(0.15)CiO(4-delta) single crystals with the size of phi5 mm x 25 min were successfully grown by traveling solvent floating zone (TSFZ) method. Good quality crystals can be verified by Laue back-scattering pattern, X-ray diffraction and scanning electron microscopy observation. For growth of Nd2CuO4 single crystals, pure O-2 was used as atmosphere and no superconductivity appeared; but pure O-2 and pure Ar-2 both cannot be used for growth of Nd1.85Ce0.15CuO4-delta single crystals. It is necessary to use Ar-O-2 mixed gas for growing as-grown superconductive Nd1.85Ce0.15CuO4-a single crystals without post-annealing treatment. From thermal dependence of resistivity curves, we found, with Ar-2/O-2 ratio raised, the transitional temperature for superconductivity of single crystals increased and the highest transitional temperature was 23.3 K in Nd1.85Ce0.15CuO4-delta single crystals obtained with Ar-2/O-2 ratio equal to 30/1, near to that of ceramic samples

Effects of CaO addition on growth of YVO4 single crystals

YVO4 single crystals doped with CaO are grown by the floating zone method in nitrogen atmosphere. The crystal is colorless and transparent after annealing in oxygen atmosphere. The effects of CaO addition are discussed. The Ca2+ ions can substitute for Y3+ at Y-sites in the YVO4 structure to form oxygen vacancies via which oxide ions can easily diffuse and, consequently, yield transparent crystals

Crystal growth of La2CuO4 and La2-xBaxCuO4 by the travelling-solvent floating zone method

La2CuO4 and La2-xBaxCuO4 single crystals have been grown by the travelling-solvent floating zone method. Suitable choice of the growth conditions is very important to obtain high-quality single crystals. It is found that the growth conditions are different for La2CuO4 and La2-xBaxCuO4. The superconducting transition temperatures of La2-xBaxCuO4 samples with different x have been measured. The effect of post-annealing has also been studied

Growth, phase transitions and properties of Li2Ti3O7 crystals

Abstract Metastable crystals of Li 2 Ti 3 O 7 of dimensions up to a diameter of 20 mm and a length of 20 mm have been grown by the Czochralski method from oriented seeds. The effects of seed orientation, growth atmosphere and dopant on crystal growth have been studied. Phase transition processes in the crystals and the H phase structure have been measured. Optical and acoustic properties of the crystals have also been determined.

Spectroscopic properties and 3-μm lasing of Er3+:YVO4 crystals

The spectroscopic properties and 3-micrometer lasing of Er3+ doped in yttrium vanadate (YVO4) were investigated in this paper. It is found that the Er3+ concentration has a negative effect on the emission of the transition 4I13/2 yields 4I15/2 (1.55 micrometer), and a positive effect on that of the 4I11/2 yields 4I13/2 transition (2.68 micrometer). With direct upper-state pumping and a plane-concave cavity a self terminating laser was achieved at the wavelength of 2.724 micrometer in the 30 at.% Er3+ doped sample. No laser activities were realized in the crystals with lower Er3+ concentrations. The laser activities of Er3+:YVO4 and Er:YAG were compared and the differences between both were discussed on the basis of the features of the upper and lower state and the population dynamics of the two levels. It is proposed that the lack of effective cross relaxations between ions in the 4I13/2 state in the Er3+:YVO4 are responsible for the termination of its 3 micrometer laser. The possible ways to improve the laser behavior were also suggested based on the discussions.