中红外激光晶体Er∶KPb_2Cl_5的原料制备和晶体生长

本文是对中红外激光晶体Er:KPb2C l5的原材料处理合成和晶体生长进行的研究报道。由于KPb2C l5的合成原料容易水解和氧化,我们设计了合适的方案对原料进行了处理,并成功合成出掺杂的稀土氯化物,然后在自制的垂直两温区晶体生长炉内,用B ridgm an法成功生长出透明的尺寸为22×10×5mm3的Er:KPb2C l5单晶体,并测试了粉末衍射和吸收光谱。     

Growth and spectral properties of Er3+/Tm3+ co‐doped LiYF4 single crystal

High quality Er³⁺/Tm³⁺:LiYF₄ single crystals were grown by a Bridgman method. The absorption spectra and luminescent properties of the crystals were studied to characterize the effect of Tm³⁺ on the spectroscopic properties upon excitation of an 800 nm laser diode. The broaden 1.5 μm and the enhanced 2.7 μm emission were observed in the Er³⁺/Tm³⁺ co‐doped LiYF₄ single crystals. Meanwhile, the up‐conversion and 1.5 μm emission intensities from Er³⁺ decrease with increasing the ratio of Tm³⁺ to Er³⁺. The energy transfer processes between Tm³⁺ and Er³⁺ in the Er³⁺/Tm³⁺ co‐doped samples were analyzed. The energy transfer efficiency η_ETE from Er³⁺ to Tm³⁺ is calculated. The highest η_ETE of 65.30% for the sample with 0.296 mol% of Er³⁺, 0.496 mol% of Tm³⁺ concentration was obtained. The present work indicates that Er³⁺/Tm³⁺ co‐doped LiYF₄ single crystal can be a promising material for the potential application in infrared devices.     

Co2+,Er3+:Y3Al5O12晶体的生长及其吸收特性

应用中频感应提拉法成功生长出新型的Co2+,Er3+:Y3Al5O12晶体.研究了室温下晶体的吸收光谱性能.结合Er3+:Y3Al5O12晶体的光谱,并利用调Q判据对Co2+,Er3+:Y3Al5O12晶体调Q特性进行了简单的分析.结果表明Co2+,Er3+:YAG晶体是一种很有潜力的自调Q激光晶体.     

New nonlinear‐laser effects in GdVO4 – host‐crystal for Ln3+ lasants

We discovered several new nonlinear‐laser χ⁽³⁾‐properties in tetragonal GdVO₄ vanadate, which is host‐crystal for lanthanide lasant ions, and attractive gain media for Raman laser converters. We hope that observed many‐phonon SRS, almost two‐octave Stokes and anti‐Stokes lasing comb, cascaded self‐frequency “tripling” and self‐sum‐frequency generation in the blue and UV spectral range could significantly enriche funcional laser potential of this crystal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of (KBr‐KCl)(OH−):(F2+)H color center laser crystal series and their spectral characteristics

In order to adjust and broaden the absorption spectrum and emission spectrum of the (F₂⁺)H type color center so as to match up to the pumping and to fit in with the demand of application, a (KBr‐KCl)(OH⁻):(F₂⁺)H color center laser crystal series was prepared by the process of single crystal growth, additive coloration, anneal, and light aggregation at 290 K and 77 K. The spectral characteristics of (KBr‐KCl)(OH⁻) crystals are investigated. It is found that the absorption and emission band of the (F₂⁺)H color centers in KBr‐KCl complex host crystals has a considerable adjustment and extensions compared to the color centers in single KBr or KCl crystal. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth of zirconium‐doped KTiOPO4 crystals in the K2O‐P2O5‐TiO2‐ZrF4 system

Zirconium‐doped KTiOPO₄ (KTP) crystals were grown using a high temperature flux method in the K₂O‐P₂O₅‐TiO₂‐ZrF₄ system. The dopant content in the single crystals with general composition KTi_1‐xZr_xOPO₄ (where x = 0 – 0.026) strongly depends on zirconium concentration in the homogeneous melts. AES‐ICP method and X‐ray fluorescence analysis were used to determine the composition of the obtained crystals. Phase analyses of the products were performed using the powder XRD. The structures of KTiOPO₄ containing different quantities of Zr were refined on the basis of single crystal XRD data. Applying ZrF₄ precursor for zirconium injection into the flux allowed growing the zirconium‐doped KTP crystals at 930–750°C. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and structure of KBi(WO4)2 single crystals

Potassium bismuth tungstate [KBi(WO₄)₂] single crystals have been grown by the top‐seeded solution growth technique. Bulk crystal with dimensions up to several centimeters is obtained for the first time. Several self‐flux systems have been used for the growth from the solution and the experiments using K₂W₂O₇ as a solvent are detailed. Powder and single crystal X‐ray diffraction of this crystal are reported. The structure refinement shows that KBi(WO₄)₂ crystallizes in the monoclinic space group C2/c, with a=10.837(3), b=10.586(3), c=7.622(2)Å, β=130.860(3)°, V=661.4(3)ų, and Z=4. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal growth of sillenite phases in the Bi2O3 ‐ TiO2 ‐ Nb2O5 system

The synthesis of Bi₂O₃‐Nb₂O₅ sillenite phase (BNbO) and the solubility of this phase with Bi₁₂TiO₂₀ was investigated by solid‐state reaction synthesis and niobium doped Bi₁₂TiO₂₀ (BTO:Nb) crystals were grown by the Top Seeded Solution Growth (TSSG) technique. The structures of polycrystalline compounds were checked by X‐ray powder diffraction method at room temperature. The correct composition of the sillenite phase stabilized with niobium was determined as Bi₁₂[Nb_0.17Bi_0.83]O_19.7 (BNbO) with unit cell parameter a = 10.261(2) Å. The system BTO‐BNbO is poorly soluble, but niobium doped BTO crystals were grown from the liquid composition 10Bi₂O₃ : xTiO₂ : (1‐x)/2 Nb₂O₅, with x = 0.95 and 0.90. A niobium concentration limit in the liquid phase is established in order to grow BTO:Nb with good crystalline quality. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and structure determination of the new silicate K3ScSi2O7

Single crystals of the new three-dimensional silicate K₃ScSi₂O₇ were obtained via a high temperature flux method and characterized by single crystal X-ray diffraction. K₃ScSi₂O₇ crystallizes in the space group P6₃/mmc with a = 5.60650(10) Å, c = 13.6420(4) Å. The structure contains sheets of ScO₆ octahedra that are connected via Si₂O₇ bridging groups.     

Crystal growth and spectral properties of Nd:Ca5(BO3)3F

A neodymium doped Ca₅(BO₃)₃F single crystal with size up to 51×48×8 mm³ has been grown by the top seeded solution growth (TSSG) technique with a Li₂O‐B₂O₃‐LiF flux. The spectra of absorption and fluorescence were measured at room temperature. According to Judd‐Ofelt (J‐O) theory, the spectroscopic parameters were calculated and the J‐O parameters Ω₂, Ω₄, Ω₆ were obtained as follows: Ω₂ = 1.41×10⁻²⁰cm², Ω₄ = 3.18×10⁻²⁰cm², Ω₆ = 2.11×10⁻²⁰cm². The room temperature fluorescence lifetime of NCBF was measured to be 51.8 μs. According to the J‐O paramenters, the emission probabilities of transitions, branching ratios, the radiative lifetime and the quantum efficiency from the Nd^{3+ 4}F_3/2 metastable state to lower lying J manifolds were also obtained. In comparasion with other Nd‐doped borate crystals, the calculated and experimental parameters show that NCBF is a promising SFD crystal.     

Flux growth and characterization of Ti‐ and Ni‐doped forsterite single crystals

Forsterite monocrystals doped with Ti and Ni were grown by the flux growth technique. A suitable mixture of flux (MoO₃, V₂O₅, Li₂CO₃) and nutrient was slowly cooled down to 750 °C from 1250 °C or 1350 °C. The crystals were then characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC). Variations observed in crystal size were attributed by both the varying experimental conditions in which they had been obtained, and to the amount of Ni substituted for Mg in the structure. High abundances of doped forsterite required a cooling rate of 1.8 K h^‐1. These synthetic, well‐characterized Ti and Ni doped forsterite crystals may have potential for exploitation in industrial fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and characterization of PbI2‐AgI binary system

The crystals of the binary system PbI₂‐AgI (PIAI) were obtained by heating the mixture of individual PbI₂ (PI) and AgI (AI) placed at 30° angle in the horizontal tubular furnace of variable temperature zone. The crystals were characterized by powder XRD, TG/DTA, FT‐IR and SEM. The 3.37% weight loss in the sample after heating at 853 K is due to the presence of water molecules absorbed (3446 cm^–1) by the crystals during sintering and cooling process. The cell parameters of the crystal were determined using the powder X‐ray data. The PbI₂‐AgI crystallizes in monoclinic system a = 10.799 (±0.009), b = 7.492 (±0.004), c = 6.929(±0.004) Å and α = 90°, β = 108.04(±0.073) γ = 90°, V = 533.18 ų. The electrical conductivity measurements of the crystals showed a sudden change in the current value at the temperature range 385–393 K. The activation energy before and after the drift was found to be 0.49 and 0.35 eV respectively. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of γ‐irradiation on spectral properties of undoped Y2SiO5 crystals

The absorption spectra of undoped Y₂SiO₅ crystals were studied before and after γ‐irradiation. After γ‐irradiation, the additional absorption peaks at 260‐270 and 320nm were observed in as‐grown and H₂‐annealed Y₂SiO₅ crystal, but it did not occur in air‐annealed Y₂SiO₅ crystal. These absorption peaks were attributed to F color centers and O^– hole centers, respectively. Owing to more oxygen vacancies and color centers in H₂‐annealed Y₂SiO₅ crystal than that in as‐grown Y₂SiO₅ crystal after γ‐irradiation, the additional absorption peaks were more intense in the former than that in the latter. With the irradiation dose increasing from 20 to 220kGy, the intensity of additional absorption peaks increased. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

The growth and spectral analysis of mixed crystal of Yb‐doped Lu0.5Y0.5PO4 mixed crystals

A new kind of 5 at% Yb‐doped Lu_0.5Y_0.5PO₄ crystals were firstly grown by spontaneously nucleated high‐temperature solution method using lead pyrophosphate (Pb₂P₂O₇) as the solvent. The X‐ray powder diffraction (XRPD) patterns recorded at room temperature showed the crystals possessed tetragonal xenotime structure. The polarized absorption spectra and the fluorescence spectra of Yb:Lu_xY_1‐xPO₄ were measured at room temperature, respectively. The results show that Yb:Lu_xY_1‐xPO₄ mixed crystal will be a promising laser material if the crystal size and quality is further improved.     

Structure and Photo‐Damage Resistance of Li‐Rich LiNbO3 Crystals Co‐Doped with Zn2+/Er3+

The pure congruent LiNbO₃, Er:LiNbO₃ and Zn,Er co‐doped Li‐rich LiNbO₃ crystals were grown by Czochralski method. The X‐ray diffraction method and ultraviolet‐visible absorption spectra of the crystals were used to analyze the structure of the crystals. The photo‐damage ability resistance of the crystals was measured. The Zn,Er co‐doped Li‐rich LiNbO₃ crystals show a decrease in lattice constant values, a shift in absorption edge of ultraviolet‐visible absorption spectra towards shorter wavelength, and three orders of magnitude increase in photo‐damage resistance compared to congruent LiNbO₃ crystal. The intrinsic and extrinsic defects are discussed to explain the enhance of the photo‐damage ability resistance     

Experimental study of bubble generation during β‐BaB2O4 single crystal growth

The generation of bubble‐inclusions during BaB₂O₄ (BBO) crystal growth from high temperature solution has been optically observed by an in situ observation technique. It was found that bubbles are formed from the peripheries of some hexagonal defects in the (0001) plane of the growing crystal, which may be caused by the evaporation of the air‐opened interface at the high temperature. In addition, atomic force microscope (AFM) was used to investigate the distribution of bubbles. Results revealed that the bubble generation and distribution depend strongly on the microscopic structure of the interface: on a rough interface, bubbles are easily formed and grow rapidly; however, they are greatly suppressed by step trains on a vicinal interface. In the latter case, the height value of a bubble is close to that of the step, which is in the order of several tens of nanometers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and electrochemical property of one‐dimensional complex: [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]2[Cu(mnt)2]

One metalorganic complex [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]₂[Cu(mnt)₂] (mnt = maleonitriledithiolate) has been obtained by the reaction of dicyclohexyl‐18‐crown‐6 with K₂mnt and CuCl₂·2H₂O. The title complex has been characterized by elementary analysis, FT‐IR, UV‐Vis spectroscopy and x‐ray single crystal diffraction. The title complex crystallizes in the triclinic space group P1 with crystallographic data: a = 10.870(6) Å, b = 11.536(6) Å, c = 12.904(7) Å, α = 101.541(10)°, β = 110.573(9)°, γ = 99.441(9)°, V = 1435.2(13) ų, Z = 1, D_calcd = 1.350 g/cm³, F(000) = 615, R₁ = 0.0641, wR₂ = 0.1475. It displays one‐dimensional chain‐like structure formed by [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]⁺ complex cations and [Cu(mnt)₂]^2‐ complex anions through N‐K‐N interactions. Its electrochemical behavior has also been studied by the cyclic voltammetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Setting Behaviour of α‐ and β‐CaSO4 · 0,5 H2O as a Function of Crystal Structure and Morphology

Calcium sulphate subhydrates (CaSO₄ · x H₂O, 0 < x ≤ 0.8) have a honeycomb‐shaped channel structure. The symmetry is either trigonal or a slight deviation thereof. Due to insufficient diffraction data and the high pseudosymmetry of the structure, it is not possible at this point to determine with certainty the specific arrangement of the water molecules in the channels. When the Fourier transformation method is used to calculate the growth form of the hemihydrate (x = 0.5), the calculated crystal form corresponds to the observed form only when the trigonal structural symmetry is largely retained. During dehydration of gypsum or, conversely, during the setting process of hemihydrate, heteroepitaxial growths of hemihydrate are observed on gypsum, or gypsum is grown heteroepitaxially on hemihydrate. The (100) faces of the hemihydrate and (010) of gypsum for the most part run parallel. Using diffraction and spectroscopic methods, it can be shown that a structural difference exists between α‐ and β‐hemihydrates, and that this difference probably accounts for the different setting behaviours. It is in this context that the presence of oxonium ions, particularly in β‐hemihydrate, found in NMR experiments is of interest. Textural studies indicated that the arrangement of gypsum crystals found in hardened gypsum is determined by the hemihydrate.     

Crystal structure and characterization of a novel organic optical crystal: 4‐chloro‐3‐nitrobenzophenone

Single crystals of a novel organic material, 4‐Chloro‐3‐Nitrobenzophenone (4C3N) were grown from acetone solution employing the technique of controlled evaporation. 4C3N belongs to the Orthorhombic system, with a = 12.9665(11) Å, b = 7.4388(6) Å, c = 24.336(2) Å, α = β = γ = 90°. FT‐IR study has been performed to identify the functional groups. The transmittance of 4C3N has been used to calculate the refractive index n; the extinction coefficient K and both the real ε_r and imaginary ε_i components of the dielectric constant as functions of photon energy. The optical band gap of 4C3N is 2.7 eV. Thermo gravimetric analysis and differential thermal analysis have also been carried out, and the thermal behavior of 4C3N crystal has been studied. The mechanical properties have been investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Unidirectional growth of α‐NiSO4·6H2O crystal by Sankaranarayanan–Ramasamy (SR) method

Large cylindrical [001] direction α‐nickel sulphate hexahydrate crystal with 20 mm diameter and 140 mm length was grown from an aqueous solution by uniaxially solution‐crystallization method of Sankaranarayanan–Ramasamy (SR). The grown crystal was examined by X‐ray diffraction, UV‐Vis‐NIR spectroscopy and TGA/DTA analysis methods.