Shifu Zhu

Growth of AgGaS2 single crystal by descending crucible with rotation method and observation of properties

This note reports a new procedure of polycrystalline synthesis and a new technique of single crystal growth on AgGaS2, i.e. two-zone temperature oscillation vapor transporting and descending crucible with rotation. A single phase dense AgGaS2 polycrystalline ingot was synthesized, and a crack-free AgGaS2 single crystal with 15 mm in diameter and 30 mm in length was grown by the techniques mentioned above. Structure integrity of the crystal was studied by the X-ray diffraction technique. Six order X-ray spectra from the 011 face of the crystal were obtained, and an anomalous phenomenon was observed for the first time that intensity of the higher order diffraction peak is much stronger than that of the lower order diffraction peak. Etch-pits of the crystal were observed by the scanning electron microscopy (SEM).

Polycrystalline Synthesis and Single Crystal Growth of AgGaS2

A modified two temperature vapor transport procedure has been used to synthesize AgGaS 2 polycrystalline materials at 1060 °C from high-purity Ag, Ga, S elements. The results showed that the polycrystalline materials are pure single phase AgGaS 2 by X-ray powder diffraction analysis. The polycrystalline ingot includes a few interior voids and has a high mass density. The AgGaS 2 ingot with 12 mm in diameter and 20 mm in length has been grown by the modified Bridgman technique in two-zone vertical furnace. As-grown AgGaS 2 ingot was characterized by the X-ray diffraction technique, obtained the rocking curve of the crystal (011) face, it is shown that the ingot is AgGaS 2 single crystal. The infrared transparent of the crystal at 2 ∼ 10 μm is 49% (and absorption coefficient is 0.74 cm -1 ).

Improved growth of AgGaSe2 crystals and phase matched second harmonic generation of 10.6 μm CO2 laser radiation

Good quality AgGaSe2 single crystal 22 mm in diameter and 80 mm in length is grown by an improved technique, i.e., descending ampoule with rotation. Although the crystals grow with optical defects, postgrowth heat treatment procedures are used to successfully eliminate the defects and produce material of 62.4% IR transmission at 10.6?m. The frequency-doubling device is cut from a cylindrical crystal boule using a new orientation cut method according to the type-1 phase-matched condition. A high optical quality, orientated AgGaSe2 single crystal of 10x 10x 12 mm size is used for second harmonic generation (SHG) of the pulsed output of a 10.6?m CO2 miniature transversely excited atmospheric laser. A relatively high energy conversion efficiency of 12% is obtained. It is found that the optical surface damage threshold of the crystal is larger than 12 MW/cm2.

Synthesis and Spectroscopic Characteristics of LiMgAlF6:RE3+ (RE = Eu, Tm, Gd)

Polycrystalline samples of single phase LiMgAlF 6 :RE 3+ (RE = Eu, Tm, Gd) are prepared by the solid state reaction method using the ratio 120/110/100 of LIF/MgF 2 /AlF 3 at 1008 K for 4 h in flowing Ar atmosphere. Their structures and spectroscopic characteristics are investigated and discussed.

New way of preparation and orientation processing of AgGaSe2 crystals

The melt temperature oscillation method (MTOM) has been used to synthesize dense single-phase AgGaSe2 polycrystalline materials, which are better than those synthesized by the conventional method. AgGaSe2 crystal 22 mm in diameter and 80 mm in length was obtained by the descending ampoule with rotation method using polycrystalline materials synthesized by MTOM. The synthesis of the polycrystalline materials and growth of AgGaSe2 single crystal were carried out in the same quartz ampoule without transfer between steps. As-grown crystal was characterized by a variety of techniques. The results demonstrated that the quality of the crystal is high. There are two cleavage faces, (112) and (101), in the as-grown crystal. The (101) cleavage face has not previously been reported. To fabricate devices, a new orientation processing technique for the AgGaSe2 crystal was developed. Wafers were cut by combining the X-ray orientation device with the standard stereogram of the (112) plane on the crystal boule with two cleavage faces, (112) and (101). Following the example of frequency-doubling devices for second harmonic generation (SHG) of the pulsed output of a 10.6 μm CO2 laser, a frequency-doubling device has successfully been fabricated by the new orientation processing technique. What is more, the method is simpler, faster, and more exact than that of the conventionally used Laue orientation method.

The distances of Co–O band in SrLaAlO4: Co2+ crystal

Based on Zhaos semi-SCF d-orbit wave functions model of free Co2+ ions, the superposition crystal field model and Macfarlanes perturbation loop method, the distances of the Co–O band in a SrLaAlO4:Co2+ crystal were determined by calculating the experimental optical spectra and EPR parameter. The agreement between the calculated result and the experimental data showed quantitatively that Co–O distances perpendicular to and parallel with the C4 axis were 0.1892 and 0.2139 nm, respectively.

Sulfonated poly(ether ether ketone)/poly(vinylidene fluoride)/graphene composite membrane for a vanadium redox flow battery

AbstractSulfonated poly(ether ether ketone)/poly(vinylidene fluoride)/graphene (S/P/G) composite membrane was prepared through a solution-casting method for a vanadium redox flow battery (VRB), and the weight ratio of high sulfonated poly(ether ether ketone) (SPEEK), polyvinylidene fluoride (PVDF), and graphene was optimized. The preferred S/P/G-7 composite membrane showed the lowest VO2+ permeability and highest ion selectivity compared with other four kinds of cation exchange membranes SPEEK75, heterogeneous PSSA-PE, Nafion 117, and recast Nafion (r-Nafion). The VRB with S/P/G-7 membrane exhibited the higher coulombic efficiency of ∼8% and energy efficiency of ∼4%, but lower capacity loss and self-discharge than that of VRB with Nafion117 membrane during cycling tests, which further indicated the promising prospects of S/P/G-7 composite membrane in VRB application. Graphical abstractᅟ

New La326 type compounds substituted with sodium and potassium

Abstract New members of La326 type compounds La 2 Ca 1− x Na x Cu 2 O 6− δ , La 2− x Sr x Ca 0.7 Na 0.3 Cu 2 O 6− δ , La 2− x K x CaCu 2 O 6− δ , and La 1.6 K 0.4 Ca 1− x Sr x Cu 2 O 6− δ were prepared with solid state reaction. Experiments show that calcination and sinter temperatures as well as the heating rate used to prepare single phase La326 type compounds substituted with sodium and potassium are lower than those used to prepare Ln 2− x A 1+ x Cu 2 O 6− δ (A=Ca, Sr). Their structures were verified with Rietveld refinement to belong to the structure type of typical La326 type compounds La 2− x A 1+ x Cu 2 O 6− δ (A=Ca, Sr). The D.C. magnetic susceptibility dependence of the temperature of the La 1.7 Sr 0.3 Ca 0.7 Na 0.3 Cu 2 O 5.86 sample shows that the sample displays a diamagnetic signal at 63 K.