Zongcheng Ling

Characterization of mixed Nd:LuxGd1−xVO4 laser crystals

A series of laser crystals Nd:LuxGd1−xVO4 (x=0.14,0.32,0.50,0.61,0.70,0.80) was grown by the Czochralski method. The thermal properties, including the average linear thermal expansion coefficients, thermal diffusion coefficients, specific heats, and thermal conductivities, of the mixed crystals were obtained. The material constants Ms for the thermal stress resistance figure were calculated and showed that the thermal fracture limits of the mixed crystals should be comparable with that of Nd:YVO4. The polarization absorption spectra from 240to1000nm were measured at room temperature and the absorption cross sections at 809nm were calculated. Using the Judd-Ofelt theory, the theoretical radiative lifetimes were calculated and compared with the experimental results. Continuous wave laser performances were achieved with the mixed crystals at the wavelength of 1.06μm when they were pumped by a laser diode. Thermal, optical, and laser properties have shown variation as a function of x and proved that the mixed...

Anisotropic thermal properties of monoclinic Yb:KLu(WO4)2 crystals

Yb:KLu(WO4)2 (KLuW) crystals with large size and good optical quality have been grown by the top-seeded solution growth (TSSG) method. The melting point and specific heat, anisotropic thermal expansion and thermal conductivity have been measured. The Jackson factor α of a series of observed faces (hkl) on Yb:KLuW crystals have been calculated. In addition, the microhardness has also been measured. We find that the thermal expansion anisotropy of Yb:KLuW is weaker than KGd(WO4)2 (KGW) and KYb(WO4)2 (KYbW) and the thermal conductivity is up to 4.4Wm−1k−1 along [205] directions at 25°C, which is the greatest in their family.

Correlated compositional and mineralogical investigations at the Chang'e-3 landing site

The chemical compositions of relatively young mare lava flows have implications for the late volcanism on the Moon. Here we report the composition of soil along the rim of a 450-m diameter fresh crater at the Chang′e-3 (CE-3) landing site, investigated by the Yutu rover with in situ APXS (Active Particle-induced X-ray Spectrometer) and VNIS (Visible and Near-infrared Imaging Spectrometer) measurements. Results indicate that this regions composition differs from other mare sample-return sites and is a new type of mare basalt not previously sampled, but consistent with remote sensing. The CE-3 regolith derived from olivine-normative basaltic rocks with high FeO/(FeO+MgO). Deconvolution of the VNIS data indicates abundant high-Ca ferropyroxene (augite and pigeonite) plus Fe-rich olivine. We infer from the regolith composition that the basaltic source rocks formed during late-stage magma-ocean differentiation when dense ferropyroxene-ilmenite cumulates sank and mixed with deeper, relatively ferroan olivine and orthopyroxene in a hybridized mantle source.

Reflectance conversion methods for the VIS/NIR imaging spectrometer aboard the Chang’E-3 lunar rover: based on ground validation experiment data

The second phase of the Chang’E Program (also named Chang’E-3) has the goal to land and perform in-situ detection on the lunar surface. A VIS/NIR imaging spectrometer (VNIS) will be carried on the Chang’E-3 lunar rover to detect the distribution of lunar minerals and resources. VNIS is the first mission in history to perform in-situ spectral measurement on the surface of the Moon, the reflectance data of which are fundamental for interpretation of lunar composition, whose quality would greatly affect the accuracy of lunar element and mineral determination. Until now, in-situ detection by imaging spectrometers was only performed by rovers on Mars. We firstly review reflectance conversion methods for rovers on Mars (Viking landers, Pathfinder and Mars Exploration rovers, etc). Secondly, we discuss whether these conversion methods used on Mars can be applied to lunar in-situ detection. We also applied data from a laboratory bidirectional reflectance distribution function (BRDF) using simulated lunar soil to test the availability of this method. Finally, we modify reflectance conversion methods used on Mars by considering differences between environments on the Moon and Mars and apply the methods to experimental data obtained from the ground validation of VNIS. These results were obtained by comparing reflectance data from the VNIS measured in the laboratory with those from a standard spectrometer obtained at the same time and under the same observing conditions. The shape and amplitude of the spectrum fits well, and the spectral uncertainty parameters for most samples are within 8%, except for the ilmenite sample which has a low albedo. In conclusion, our reflectance conversion method is suitable for lunar in-situ detection.

Spatial distributions of secondary minerals in the Martian meteorite MIL 03346,168 determined by Raman spectroscopic imaging

Miller Range (MIL) 03346 is a nakhlite meteorite that has been extensively studied due to its unique complex secondary mineral phases and their potential implications for the hydrologic history of Mars. We conducted a set of Raman spectroscopic and Raman imaging studies of MIL 03346,168, focusing on the secondary mineral phases and their spatial distributions, with a goal to better understand the possible processes by which they were generated on Mars. This study revealed three types of calcium sulfates, a solid solution of (K, Na)-jarosite and two groups of hydrated species with low crystallinity (HSLC) in the veins and/or mesostasis areas of the meteorite. The most abundant Ca-sulfate is bassanite that suggests two possible paths for its direct precipitation from a Ca-S-H2O brine, either having low water activity or with incomplete development (producing bassanite with gypsum microcrystals) on Mars. The second most abundant Ca-sulfate is soluble γ-CaSO4 which raises a new question on the origins of this phase in the Martian meteorite, since γ-CaSO4 readily hydrates in the laboratory but is apparently stable in Atacama Desert. The close spatial relationship of (K, Na)-jarosite solid solutions with rasvumite (KFe2S3), magnetite, HSLC, and fine-grained low-crystallinity alkali feldspar in mesostasis suggests a potential in situ formation of mesostasis jarosite from these Fe-K,Na-S-O-H2O species.

Diode-pumped Q-switched intracavity frequency-doubled Nd:LuVO4/KTP green laser

A simple and compact diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:LuVO4/KTP green laser were demonstrated successfully for the first time. At an incident pump power of 6.5 W, an average output power of 663 mW, a pulse width of 26 ns were obtained with a PRF of 10 kHz. The pulse energy and peak power of the green light were determined to be 66.3 μJ and 2.55 kW, respectively.

How does the multiple constituent affect the carrier generation and charge transport in multicomponent TCOs of In–Zn–Sn oxide

The main purpose of this work is to make clear that in the newly synthesized multicomponent materials IZTO, namely, Sn/Zn cosubstituted In2O3, how can these cosubstituted dopants interact with each other and affect the electronic properties. We carry out a series of systematic Density Functional Theory calculations. Compared with ITO materials, the existence of Zn2+ in IZTO is important for the control of the electronic properties. Although there is large lattice distortion in the local structure around Zn2+ due to the Jahn–Teller effect, it releases distortions induced by other defects and thus reduces the formation energy of cosubstitution of the Zn/Sn impurity pair in In2O3. The VO defect prefers to form in the ZnO6 octahedron for the breaking of the Zn–O bond is easier than the Sn–O bond, which generates free electrons. In all IZTO configurations with and without defects, the bottom of conduction bands is comprised mainly of cation-s and O-p orbitals, which constructs a three dimensional network for charge transport. The bandstructure renormalization effect exerted by Zn atoms narrows the band gap. The existence of Zn atoms, on the one hand, weakens the spatial localization and orbital localization effects induced by defects and on the other hand strengthens the charge transport ability. These results indicate that the multicomponent semiconductor IZTO is an excellent candidate for the low indium content TCOs. Our work is useful to control the physical properties of IZTO experimentally, and is also helpful in understanding other multicomponent TCO materials.

Lattice vibration and thermal diffusion of Yb doped KLu(WO4)2 single crystal

Yb doped KLu(WO4)2 (Yb:KLuW) single crystal was grown by the method of top-seeded-solution growth slow-cooling method. Its lattice vibrational modes were calculated by using space group theory, and polarized Raman spectra were measured at room temperature with different scattering geometry projections. The powder transmission of Fourier-transform infrared spectra was also performed as a supplement for Raman spectra to study the lattice vibration of the laser crystal. The main Raman peaks and infrared transmission bands were attributed to the internal mode WO6 octahedrons in the crystals. Two kinds of link ways of WO6 octahedrons implying large distortion had led the Raman peaks to shift to different positions. Large distortions of the WO6 octahedrons in the crystal had led to the splitting of some Raman peaks and even the activation of ν6 mode, which is originally a silent mode by the selection rule. As a self-Raman crystal, the linewidth of the Raman peaks ν1 and ν2 reached 12.5 and 16.6cm−1, with relaxa...

Geometric, electronic and optical properties of zinc/tin codoped In2O3 modulated by the bixbyite/corundum phase transition

As transparent conducting oxides (TCOs), In2O3 in the high pressure phase attracts extensive research interests. Because physical properties are determined by the geometric structures, we investigate the electronic and optical properties of Zn/Sn codoped In2O3 materials (IZTO) being modulated by the bixbyite/corundum phase transition via Density Functional Theory calculations. For IZTO in high pressure phase, i.e. corundum phase, Sn/Zn dopant pair tends to form face-sharing ZnO6 and SnO6 octahedrons. The radius differences between Zn2+/Sn4+ dopants and In3+ host cations make Jahn-Teller effect occur and IZTO transform from bixbyite to corundum phase under a slight higher pressure than that of pure In2O3. Although Zn/Sn cosubstitution of In ions may increase the free carrier effective mass m * near the band edge, when IZTO crystal transforms to corundum phase, the more dense packing structure results in stronger cation s-orbital overlaps than in bixbyite phase, which makes m * recover to a smaller value. In addition, corundum IZTO has a larger indirect band gap and a high dopant solubility. So these investigations may open a new way to search for TCOs materials with low indium content.

Correlation analysis and partial least square modeling to quantify typical minerals with Chang’E-3 visible and near-infrared imaging spectrometer’s ground validation data

In 2013, Chang’E-3 program will develop lunar mineral resources in-situ detection. A Visible and Near-infrared Imaging Spectrometer (VNIS) has been selected as one payload of CE-3 lunar rover to achieve this goal. It is critical and urgent to evaluate VNIS’ spectrum data quality and validate quantification methods for mineral composition before its launch. Ground validation experiment of VNIS was carried out to complete the two goals, by simulating CE-3 lunar rover’s detection environment on lunar surface in the laboratory. Based on the hyperspectral reflectance data derived, Correlation Analysis and Partial Least Square (CA-PLS) algorithm is applied to predict abundance of four lunar typical minerals (pyroxene, plagioclase, ilmenite and olivine) in their mixture. We firstly selected a set of VNIS’ spectral parameters which highly correlated with minerals’ abundance by correlation analysis (CA), and then stepwise regression method was used to find out spectral parameters which make the largest contributions to the mineral contents. At last, functions were derived to link minerals’ abundance and spectral parameters by partial least square (PLS) algorithm. Not considering the effect of maturity, agglutinate and Fe0, we found that there are wonderful correlations between these four minerals and VNIS’ spectral parameters, e.g. the abundance of pyroxene correlates positively with the mixture’s absorption depth, the value of absorption depth added as the increasing of pyroxene’s abundance. But the abundance of plagioclase correlates negatively with the spectral parameters of band ratio, the value of band ratio would decrease when the abundance of plagioclase increased. Similar to plagioclase, the abundance of ilmenite and olivine has a negative correlation with the mixture’s reflectance data, if the abundance of ilmenite or olivine increase, the reflectance values of the mixture will decrease. Through model validation, better estimates of pyroxene, plagioclase and ilmenite’s abundances are given. It is concluded that VNIS has the capability to be applied on lunar minerals’ identification, and CA-PLS algorithm has the potential to be used on lunar surface’s in-situ detection for minerals’ abundance prediction.