Growth of dysprosium garnet single crystals with spiral shape using Czochralski technique

The growth conditions of dysprosium garnets single crystals, to obtain a long and good spiral shape crystal, have been investigated using the conventional Czochralski technique along the [111] pulling direction. The good spiral shape of Dy₃Ga₅O₁₂ single crystal with 40 mm in length is grown with its spiral pitch and spiral diameter of 20 mm and 15 mm, respectively.     

Growth of Lithium Niobate Single Crystal Fiber by an Edge–defined,Film-fed Growth Method

Lithium Niobate (LiNbO₃) single crystal fiber with 0.5 mm in diameter and 160–170mm long have been grown by an edge-defined, film-fed growth (EFG) technique. The morphology and microcracks of the fiber are studied. The mechanism of forming a single domain structure in the as-grown LiNbO₃ crystal fiber is discussed on the basis of the thermoelectric field model.     

Polycrystalline Synthesis and Single Crystal Growth of AgGaS2

A modified two temperature vapor transport procedure has been used to synthesize AgGaS₂ polycrystalline materials at 1060 °C from high-purity Ag, Ga, S elements. The results showed that the polycrystalline materials are pure single phase AgGaS₂ by X-ray powder diffraction analysis. The polycrystalline ingot includes a few interior voids and has a high mass density. The AgGaS₂ 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 AgGaS₂ 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 AgGaS₂ single crystal. The infrared transparent of the crystal at 2 ∼ 10μm is 49% (and absorption coefficient is 0.74 cm^—1).     

Growth of PbI2 single crystal by the top seed vertical zone melting method

PbI₂ is a type of syntectic compound, and its single crystal is one of the room temperature semiconductor nuclear radiation detector materials. A new method for the growth of the PbI₂ single crystal is proposed in this article, which was named the top seed vertical zone melting method (TSVZMM), directly from the synthesis of polycrystal with analytically pure lead and iodine, by controlling the decomposition and stratification of the melt and the stoichiometry of the PbI₂ crystal. Impurities in the crystal and the coagulating droplets of lead were eliminated during the PbI₂ crystal growth process from the top to bottom by TSVZMM. The PbI₂ single crystal was successfully grown with the size of Φ15 mm×15 mm, an infrared transmittance of more than 40%, a resistivity of 2×10¹² Ω cm magnitude and stoichiometry close to its theoretical value.     

A new optical medium—Cd<Subscript>0.75</Subscript>Sr<Subscript>0.25</Subscript>F<Subscript>2</Subscript> single crystals

For the first time, single crystals of the Cd_0.75Sr_0.25F₂ solid solution with the fluorite structure are grown from melt by the Bridgman-Stockbarger method. The composition of these single crystals corresponds to the composition congruently melting at the minimum point on the phase diagram. The maximum diameter of the crystal is 50 mm; the maximum height is 30 mm. The vickers microhardness of the semitransparent crystals equals 191 ± 43 kg/mm². The transmission cutoff in the IR range is ～10 μm.     

Growth and Properties of BeO · 3 Al2O3 (BHA) Single Crystals

Large single crystal of BeO · 3 Al₂O₃ (beryllium hexa-aluminate or BHA) doped with chromium up to 20 mm in maximum diameter and 60 mm long were grown by Czochralski method. Thechnological conditions of crystal growth have been introduced and key factor leading to a successful growth is a adequate composition of starting charge mixture other than stoichiometry. The crystal structure, absorption spectra and fluorescence spectra of BHA: Cr³⁺ have been measured. Vibronic side band of the fluorescence spectra is from 700 nm to 900 nm.     

Fluorescence properties of Nd3+ doped stoichiometric LiNbO3 fiber single crystals by micro‐pulling down method

Using the micro‐pulling down (μ‐PD) method, 1 and 3 mol% Nd₂O₃ doped near stoichiometric lithium niobate (LiNbO₃) single crystal fibers were grown in 1 mm diameter and 35∼40 mm length. The grown crystal fibers were free of cracks and the homogeneous distribution of Nd³⁺ ion concentrations were confirmed by the electron probe micro analysis. The changes of fluorescence spectra were measured with respect to the Nd³⁺ ion doping concentration. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies of the Growth Habits of the AgGaSe2 Single Crystal

High quality AgGaSe₂ single crystals with 20 mm in diameter and 55 mm in length have been grown by the modified Bridgman technique and the growth habits of AgGaSe₂ single crystals have been investigated in detail. It is found that the shape of the growth ampoule affects greatly the nucleation and the growth of AgGaSe₂ single crystal. A new cleavage face (101) and the natural faces are observed in the as-grown crystals. For some cases, the growing direction is normal to the (316) face.     

Properties of AgGa1‐xInxSe2 single crystals grown by Bridgman method

High‐pure and single‐phase AgGa_1‐xIn_xSe₂ (x=0.2) polycrystalline was synthesized by the mechanical and temperature oscillation method. Adopting the modified Bridgman method an integral AgGa_1‐xIn_xSe₂ single crystal with diameter of 14 mm and length of 35 mm has been obtained at the rate of 6 mm/day. It was found that there is a new cleavage face which was (101), and observed the four order X‐ray spectrum of the {101} faces. By the method of DSC analysis the melting and freezing points of the AgGa_1‐xIn_xSe₂ (x=0.2) single crystal were about 828°C and 790°C. The transmission spectra of the AgGa_1‐xIn_xSe₂ (x=0.2) sample of 5×6×2 mm³ were obtained by means of UV and IR spectrophotometer. The limiting frequency was 774.316nm and the band gap was 1.6eV. It can be found in the infrared spectrum that the infrared transmission was above 60% from 4000cm^‐1 to 600cm^‐1. The value of α in 5.3µm and 10.6µm were 0.022cm^‐1 and 0.1cm^‐1 respectively. All results showed that the crystal was of good quality. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of CdGeAs2 crystal by modified vertical Bridgman method

A large, crack-free CdGeAs₂ single crystal measuring 15 mm in diameter and 45 mm in length was grown in a vertical three-zone tubular furnace by a modified vertical Bridgman method, i.e. quasi-seed technique with small temperature gradient and descending quartz ampoule. High-purity, single phase CdGeAs₂ polycrystallite for crystal growth was synthesized using a rocking furnace with temperature oscillation techniques. Various measuring means, including X-ray diffractometer(XRD), Fourier transform infrared spectroscopy(FTIR), and Field emission scanning electron microscope(FE-SEM) were adopted to characterize the as-grown crystal. It is found that the cleavage plane of the as-grown crystal is {1 0 1} face; the crystal is integrated in structure and crystallized well; etch pits in the shape of pentagon on (1 1 2) face have been observed for the first time using the new preferential etchant we prepared. All these results encouragingly indicate that the modified vertical Bridgman method is a convenient and effective way for high quality CdGeAs₂ crystal growth.     

TEM and X-ray investigations of defect structure of PbSnTe crystal

The Pb_0.8Sn_0.2Te single crystal grown by the Bridgman technique was examined by X-ray and TEM methods. The X-ray reflection topography revealed that the PbSnTe crystal consisted of monocrystallinic blocks with linear dimensions of 1–5 mm separated by low angle boundaries of tilt-twist character. “As grown” defects observed by TEM method have been identified as single perfect dislocations and dislocation pairs. A mean density of dislocations inside the crystal blocks was no more than 10³ cm⁻². Except “as grown” defects rows of mobile dislocations were observed. All of dislocations lines were characterized by the same type of Burgers vector, i.e. b = 1/2a〈110〉.     

Synthesis and characterization of PbI2 polycrystals

Single‐phase PbI₂ polycrystalline material for single crystal growth was synthesized by two‐temperature vapor‐transporting method (TVM), directly from highly pure lead and iodine with excess lead without according to the PbI₂ stoichiometry. It is found that there is an immiscible phenomenon of two melts in the synthesis experiment, and the melts solidified until cooled down to room temperature. X‐ray diffraction (XRD) analysis and Energy dispersive X‐ray (EDX) microanalysis indicate that the solidified materials are single‐phase PbI₂ polycrystal and nearly pure lead. Considering the observed immiscible phenomenon and the data given in paper [1], it is able to confirm that there is a new immiscible region L₂+L₃ in Pb‐I phase diagram, which is very important to PbI₂ polycrystal synthesis and single crystal growth. Using single‐phase PbI₂ polycrystalline material synthesized by our method, PbI₂ single crystal with size of ?15mm×30mm was grown by vertical Bridgman method. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Crystal Growth and Differential Thermal Analysis of AgGaSe2

High quality AgGaSe₂ single crystals with 20 mm in diameter and 55 mm in length have been grown by Bridgman technique. It is found that there is a second phase of Ag-rich Ga₂Se₃ (or named AgGa₇Se₁₁) in the AgGaSe₂ crystal. It is concluded by discussions with the DTA results and the phase diagram that single crystals grown from polycrystalline materials with stoichiometric composition must contain a second phase of Ag-rich Ga₂Se₃. This result is helpful for the heat treatment, in which what and how much is added and what temperature is chosen for the heat treatment, are very important.     

Solution growth of new ferroelectric glycine phosphite unidirectional single crystals at room temperature

Glycine phosphite [NH₃CH₂COOH₃PO₃], abbreviated as GPI is the second hydrogen bonded ferroelectric crystal combination of phosphorous acid and amino acid following βnine phosphite crystals abbreviated as BPI. Sankaranarayanan and Ramasamy‐Technique was adopted to prepare the ferroelectric glycine phosphite unidirectional single crystal. The growth orientation was imposed by the pre‐grown 〈010〉 seed. As water was the solvent, transparent, colourless crystal with cylindrical shaped ingot of sized 20mm‐diameter was grown. Powder X‐ray diffraction, HRXRD, FTIR, dielectric and mechanical studies were carried out. The results are discussed in detail. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and dielectric properties of Ta2O5 single crystal by the floating zone method

Large Ta₂O₅ single crystal with high‐dielectric permittivity was successfully grown by floating zone (FZ) method under air atmosphere. The grown crystal that has been obtained was typically about 8 mm in diameter and 90 mm in length. The crystal growth parameters were optimized. The crystal symmetry, characterized by means of X‐ray diffraction (XRD), was found to be tetragonal. The relative permittivity and loss tangent along growth and [001] direction were measured in the temperature range between ‐200 °C and 200 °C, which showed a strong dielectric anisotropy. At a frequency of 1 MHz and 20 °C, the dielectric permittivity along the growth direction and [001] direction are 81.17 and 25.04 respectively. The stabilization of high‐temperature phase can explain the dielectric enhancement.     

High‐quality LaCoO3 single crystal grown by optical floating zone method and its electromagnetic properties

A LaCoO₃ single crystal with 4 mm in diameter and 30 mm in length has been grown by optical floating zone method. The as‐grown crystal is highly crystalline with the rhombohedral perovskite structure (R3c) and grows parallel to the (121) direction. The room temperature resistivity of the as‐grown crystal is 0.12 Ω·cm and the insulator‐metal transition occurs around 500 K. The coercivity and the remanence of the as‐grown crystal are 5 Oe and 6.61×10^–5 μ_B/f.u. at 5 K, respectively. In 1000 Oe under zero‐field cooling, the magnetic susceptibility of the as‐grown crystal shows an upturn in a Curie tail fashion below 35 K, and appears a wave crest over the interval 55 K≤T≤90 K. In addition, a slope change of 1/χ(T) at about 12 K is observed in 50000 Oe under zero‐field cooling. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of KBi(WO4)2 single crystals

Potassium bismuth tungstate [KBi(WO₄)₂] single crystals with dimensions up to 20 mm × 15 mm × 15 mm have been successfully grown by using the top‐seeded solution growth technique and K₂W₂O₇ as solvent. Experiments show that this crystal is unstable in a strong acid or alkali environment and has a blue fluorescence emission. The density, hardness, melting point, absorption edge, transparency range, prominent Raman shift frequency are 7.57 g/cm³, 238 kg/mm², 800 °C, 380 nm, 400–5450 nm, 868 cm^–1 respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature gradient controlled growth and optical properties of Er:BaY2F8 crystals

Single crystals of Erbium (Er) doped BaY₂F₈ have been obtained by the temperature gradient technique (TGT). No‐seed‐grown crystal of Er:BaY₂F₈, with the dimensions up to several centimeters, was obtained by self‐crystallization. The optimizations of various growth parameters were systemically investigated. The results indicated that the temperature gradient of 6‐7 K/mm and the cooling velocity less than 6 K/h were suitable for the crystal growth. The XRD data and the investigations on the growth striations by a stereo polarization microscope displayed that the [001] direction is the dominating direction for the crystal growth. The crystal grown by TGT often cracks along with the (100) plane, which is caused by the excessive decrease of the temperature during the crystal growth, for there is a rapid change in the thermal expansion curve of the BaY₂F₈ crystal in the temperature range from 800 °C to 900 °C. The spectral properties of Er:BaY₂F₈ single crystals have been studied and the effects of frequency up‐conversion of the crystals are reported. Spectral data suggest that the quality of Er:BaY₂F₈ crystal obtained by TGT method is good and the crystal has the potential application in laser devices. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations on the Growth and Laser Properties of Nd:GdVO4 Single Crystal

In this paper, we report the growth of laser crystal Nd:GdVO₄ by the Czochralski method, and discuss the morphology of the crystal. The polarization absorption and emission spectra of Nd:GdVO₄ were measured. The lifetime of the Nd:GdVO₄ at 1064 nm is 100μs. An output power up to 1 W at 1064 nm has been achieved with a 3 mm × 3 mm × 1 mm crystal sample when pumped by a 1.9 W cw laser diode.     

Growth of Nd:Sr3Ga2Ge4O14 crystals by a modified Bridgman method

Bridgman growth of Nd:SGG (Sr₃Ga₂Ge₄O₁₄) crystals has been investigated for the first time. Pt crucible of ∅︁25mm×250mm with a seed well of ∅︁10mm×80 mm is used, and seed is SGG crystal of ∅︁10mm×50mm grown by Bridgman method in advance. The growth parameters are optimized as the furnace temperature is set to 1450∼1500°C, temperature gradient in the crystal‐melt interface is less than 25 K/cm and growth rate is less than 0.5mm/h. The Nd:SGG crystals with 25mm in diameter and 60mm in length are grown successfully from 1.5 to 8at% Nd³⁺ doped stoichiometric Sr₃Ga₂Ge₄O₁₄ melt. The distribution coefficient and concentration of Nd³⁺ in Nd:SGG crystals are obviously higher than those of Nd:YAG crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)