Growth and scintillation properties of the Na2W2O7 crystal

The growth and scintillation properties of the Na₂W₂O₇ crystal are reported. The solid reaction between Na₂CO₃ and WO₃ is used to synthesise the Na₂W₂O₇ material. The Na₂W₂O₇ single crystal has been grown by the Bridgman method. And the Na₂W₂O₇ single crystal with sizes 14×7×6 mm³ has been achieved. The transmission spectra, the Ultraviolet fluorescence spectra and the X-ray excited luminescence spectra of the Na₂W₂O₇ crystal are measured. The measurement results show that the Na₂W₂O₇ crystal is a promising intrinsic scintillator.     

Nd:YVO4 crystal growth by Czochralski technique with a submerged plate

This paper is to investigate the growth of Nd:YVO₄ (yttrium vanadate) crystal by the modified Czochralski technique with a submerged plate. Numerical studies are performed to examine melt convection and heat transfer during Nd:YVO₄ growth. The attention is paid to study the effects of initial elevation of the submerged plate, crystal diameter, and melt level on melt inclusions. It is found that the increase in crystal rotation rate and crystal diameter, and the decrease in melt level will increase the axial temperature gradient at the edge and in the center of the crystal, and change the interface shape from convex to flat. The experiments are also carried out to confirm the feasibility of the proposed new technique for controlling melt inclusions in Nd:YVO₄ crystal growth.     

Growth of Na modified potassium lithium niobate crystal by the Czochralski method

Transparent Na modified potassium lithium niobate (Na_0.23K_2.60Li_1.82Nb_5.35O_15.70; NKLN) crystal was successively grown by the Czochralski method using RF induction heating from melt composition Na₂O:K₂O : Li₂O:Nb₂O₅=2:30:25:43 mol%. NKLN crystal showed a tetragonal tungsten bronze structure with lattice constants a=12.5446±0.0010 Å and c=4.0129±0.0005 Å at room temperature. The dielectric constant along the c-axis ε₃₃ showed a sharp maximum around 480 °C. Optical transmission edge was 370 nm and optical transmission spectra showed no absorption at wavelengths ranging from 380 to 800 nm. The structural and optical properties of NKLN were similar to those of the near stoichiometric KLN crystals. We believe that the growth of NKLN by the Czochralski method has an advantage for a large size and high-quality crystal.     

Growth of NaBi(WO4)2 crystal by modified-Bridgman method

NaBi(WO₄)₂ (NBW) crystals have been grown for the first time by modified-Bridgman method. Influences of some factors on the crystal growth process are discussed. X-ray powder diffraction experiments show that the unit cell parameters of NBW crystal are a=b=0.5284 nm, c=1.1517 nm, and V=0.3215 nm³. The differential thermal analysis shows that the NBW crystal melts at 923°C.     

Controlled synthesis of different morphologies of BaWO4 crystals via a surfactant-assisted method

BaWO₄ crystals with different morphologies, such as nanosheets, nanobelts, flower-like, quadrangled plates and sheaves of dendrite, have been successfully synthesized via PVP as templates. Our result shows that reaction parameters, such as the concentration of PVP aqueous solutions, pH value of the starting solution and molar ratio of [Ba²⁺]/[WO₄²⁻] played important roles in the formation of BaWO₄ crystal with different morphologies. It is obviously different between microwave irradiation heating and oil bath heating. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and electron diffraction.     

Growth, refined structural and spectroscopic characteristics of Tm-doped NaGd(WO4)2 single crystals

The details of Tm³⁺-doped NaGd(WO₄)₂ single-crystal growth are discussed, the results of precise investigations of its structural and spectroscopic characteristics, as well as the analysis of cross-relaxation process of Tm³⁺ ions (³H₄→³F₄, ³H₆→³F₄) in this crystal are presented. Based on the Judd–Ofelt theory, three intensity parameters, spontaneous emission probabilities, fluorescence branching ratios and fluorescence quantum efficiency from ³H₄ and ³F₄ levels were refined.     

Growth and spectral properties of Nd:LaVO4 crystal

This paper reports the growth and spectral properties of 3.5 at% Nd³⁺:LaVO₄ crystal with diameter of 20×15 mm² which has been grown by the Czochralski method. The spectral parameters were calculated based on Judd–Ofelt theory. The intensity parameters Ω_λ are: Ω₂=2.102×10⁻²⁰ cm², Ω₄=3.871×10⁻²⁰ cm², Ω₆=3.235×10⁻²⁰ cm². The radiative lifetime τ_r is 209 μs and calculated fluorescence branch ratios are: β₁(0.88μm)=45.2, β₂(1.06μm)=46.7, β₃(1.34μm)=8.1. The measured fluorescence lifetime τ_f is 137 μm and the quantum efficiency η is 65.6%. The absorption band at 808 nm wavelength has an FWHM of 20 nm. The absorption and emission cross sections are 3×10⁻²⁰ and 6.13×10⁻²⁰ cm², respectively.     

Growth, thermal and spectral properties of Nd-doped NaGd(MoO4)2 crystal

Nd³⁺-doped NaGd(MoO₄)₂ crystal with dimensions were grown by Czochralski method. Nd³⁺:NaGd(MoO₄)₂ crystal melts at 1182 °C. The hardness of Nd³⁺:NaGd(MoO₄)₂ crystal is 334 VDH. The specific heat is 72.6 cal/mol K. The thermal expansion coefficients are for c-axis and for a-axis, respectively. The absorption cross-sections of Nd³⁺:NaGd(MoO₄)₂ crystal are with a FWHM of 9 nm at the 804 nm for π-polarization and with a FWHM of 17 nm at 807 nm for σ-polarization, respectively. The emission cross-section σ_em are at 1063 nm for π-polarization and 1.94×10^-20 at 1070 nm cm² for σ-polarization, respectively. The fluorescence lifetime τ_f is 93.9 μs at room temperature.     

Influence of trivalent ions codoping on the Mo:PbWO4 luminescence properties

Trivalent ions codoping Mo:PWO boules were grown along the c-axis using the Czochralski technique. Trivalent ions codoping improved the fast components of luminescence for Mo:PWO due to suppression/compensation of hole-trapping centers. Correspondingly, trivalent ions codoping increased the fast components of the light yield. The La³⁺ and Gd³⁺ concentration in the crystal gradually decreased along the growth direction because they increased the melting point. The Y³⁺ concentration increased along this direction due to the different influence on the melting point. Compared with La:Mo:PWO, Y:Mo:PWO shows a more uniform transmittance along the growth direction.     

Growth and properties of Nd:Lu3Ga5O12 laser crystal by floating-zone method

Neodymium (Nd) doped lutetium gallium garnet (Nd:Lu₃Ga₅O₁₂, Nd:LuGG) single crystal was successfully grown by the optical floating-zone method for the first time to our knowledge. Its absorption and luminescence spectra at room temperature were measured. By using the J–O theory, the spectral parameters of Nd:LuGG were calculated, which indicated that Nd:LuGG should possess comparable and even better laser properties than Nd:YAG. The maximum output power of 855 mW at 1062 nm was achieved with slope efficiency of 23.4% under a pump power of 5.2 W, and optical conversion efficiency of 16.4%. All the results show that Nd:LuGG is a potential laser material.     

Sn3O4 single crystal nanobelts grown by carbothermal reduction process

This article reports on the growth of single crystal Sn₃O₄ nanobelts and SnO by a carbothermal reduction process in two different regions of a furnace tube. Even though intermediate tin oxide compounds (Sn₃O₄) have been observed experimentally, the study of structures based on them is a challenging task. Characterization data allowed us to propose that Sn₃O₄ nanobelts grew by vapor–solid mechanism while SnO grew by self-catalyst vapor–liquid–solid mechanism. Electrical measurements of a single Sn₃O₄ nanobelt were performed at different temperatures, revealing undoped semiconductor characteristics.     

Growth and optical properties of self-frequency-doubling laser crystal Yb:LuAl3(BO3)4

Single crystal of Yb:LuAl₃(BO₃)₄(Yb:LuAB) was grown by the flux method for the first time. The cell parameters of the grown crystal were estimated by X-ray diffraction analysis. The result indicates the symmetry of trigonal space group R32, with lattice parameters a=b=9.26372 Å, c=7.21405 Å, V=536.14 Å³, and Z=4. The absorption and emission spectra of Yb:LuAB crystal at room temperature has also been studied. The fluorescence lifetime for Yb:LuAB crystal is about 1.48 ms. The heat capacity was measured from 25 to 500 °C. Its second harmonic generation efficiency in LuAl₃(BO₃)₄ crystal is 3–4 times that of KDP crystal. These results show that Yb:LuAB crystal would be a potential self-frequency-doubling laser crystal.     

The growth and spectroscopic characteristics of Ca3Y2(BO3)4:Er laser crystal

The Ca₃Y₂(BO₃)₄:Er³⁺ crystal with a size up to 20 mm×30 mm was grown by the Czochralski method. The absorption spectrum was measured and its absorption peaks were assigned to the corresponding transitions between the Er³⁺ energy levels. A broad emission spectrum from 1429.4 to 1662.8 nm was exhibited from 530 nm wavelength pumping. This crystal is promising as a tunable infrared laser crystal.     

Large-size and high-quality Zn2TiO4 single crystal grown by the optical floating zone method

Crack-free and transparent Zn₂TiO₄ single crystals of 4–6 mm in diameter and 30 mm in length have been grown by the optical floating zone method. The powder X-ray diffraction (XRD) results show that the as-grown crystals have the spinel-type Zn₂TiO₄ structure. XRD² measurements on Zn₂TiO₄ wafers cut perpendicular to the growth direction display only one peak at 42.7°, which indicates that the Zn₂TiO₄ single crystals grow along the 〈4 0 0〉 direction (a-axis). The formation of bubble inclusions was effectively suppressed by lowering rotation rate. Transmission polarized-light microscopy results showed that as-grown crystals were free of low angle grain boundaries.     

Bulk crystal growth of congruent MgO-doped LiNbO3 crystal with stoichiometric structure and its second-harmonic-generation properties

A new LiNbO₃ bulk crystal has been grown by doping with MgO (cs-MgO:LN; Li₂O:Nb₂O₅:MgO=45.30:50.00:4.70, (Li_0.906Mg_0.047V^Li_0.047)NbO₃), which successfully has the congruent point coinciding with the stoichiometric point. Its second-harmonic-generation (SHG) properties were evaluated. It was found that cs-MgO:LN has a much more homogeneous composition leading to uniform in-plane distribution of the non-critical phase-matching wavelength than the conventional LiNbO₃ crystals such as congruent LiNbO₃ (c-LN), stoichiometric LiNbO₃ (s-LN), and MgO-doped congruent LiNbO₃ (5MgO:LN). This homogeneity arose from the observation that none of the solute components including ionic species were segregated at the interface during growth. The SHG conversion efficiency of cs-MgO:LN is comparable to those of s-LN and 5MgO:LN.     

Growth and spectral properties of Nd-doped Sr3Y(BO3)3 crystal

A new crystal of Nd³⁺:Sr₃Y(BO₃)₃ with dimension up to 25×35 mm² was grown by Czochralski method. Absorption and emission spectra of Nd³⁺: Sr₃Y(BO₃)₃ were investigated . The absorption band at 807 nm has a FWHM of 18 nm. The absorption and emission cross sections are 2.17×10⁻²⁰ cm² at 807 nm and 1.88×10⁻¹⁹ cm² at 1060 nm, respectively. The luminescence lifetime τ_f is 73 μs at room temperature     

Thermal and laser properties of Yb:YAl3(BO3)4 crystal

Large optical-quality Yb:YAl₃(BO₃)₄(Yb:YAB) crystals have been grown by the flux method. The thermal properties of Yb:YAB crystal were measured for the first time. The thermal properties of Yb:YAB crystal with different Yb³⁺ ion concentrations are also reported. The results show that the ytterbium concentration influences the properties of Yb:YAB crystal. The specific heat decreases with the increase of Yb³⁺ ion concentrations in the experiment range. Apparently, the thermal expansion coefficient increases along the c-direction with the increase of Yb³⁺ ion concentrations, while it changes slightly along the a-direction. The output laser in 1120–1140 nm ranges has been demonstrated pumped by InGaAs laser. The slope efficiency is 3.8%. The self-frequency-doubling output power of 1 mW is achieved.     

Crystal growth and spectroscopic properties of Yb:CaYAlO4 single crystal

A Yb³⁺-doped CaYAlO₄ laser crystal has been grown by the Czochralski technique. The segregation coefficient was measured by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The cell parameters were analyzed with X-ray diffraction experiments. Color defects in Yb:CaYAlO₄ have been evidenced to be similar to those in undoped CaYAlO₄. The polarized absorption spectra and the fluorescence spectrum of the Yb:CaYAlO₄ crystal were measured at room temperature. The fluorescence decay time of the Yb³⁺ ion was investigated. The results show that Yb:CaYAlO₄ has potential as a laser gain medium for an ultrashort laser system.     

Growth and Raman spectroscopic characterization of As4S4 (II) single crystals

As described by Kutoglu (1976 [16]), single crystals of As₄S₄ (II) phase have been grown using a new two-step synthesis that drastically increases the reproducibility that is attainable in synthetic experiments. First, through photo-induced phase transformation, pararealgar powder is prepared as a precursor instead of AsS melt. Then it is dissolved and recrystallized from CS₂ solvent. Results show that single crystals of the As₄S₄ (II) phase were obtained reproducibly through the dissolution–recrystallization process. Single crystals of As₄S₄ (II) obtained using this method were translucent and showed a uniform yellow-orange color. The crystal exhibits a platelet-like shape as a thin film with well-developed faces (0 1 0) and (0 1¯ 0). The grown crystals are as large as 0.50×0.50×0.01 mm. They were characterized using powder and single crystal X-ray diffraction techniques to confirm the phase identification and the lattice parameters. The As₄S₄ (II) phase crystallizes in monoclinic system with cell parameters a=11.202(4) Å, b=9.954(4) Å, c=7.142(4) Å, β=92.81(4)°, V=795.4(6) Å³, which shows good agreement with the former value. Raman spectroscopic studies elucidated the behavior of the substance and the relation among phases of tetra-arsenic tetrasulfide.     

Growth and characterization of KY(WO4)2 crystals

Single-crystal growth of KY(WO₄)₂ (KYW) by top-seeded solution growth technique has been investigated. The effects of seed orientation, temperature gradient experienced by the growing crystal and rate of crystallization on crystal quality are reported. The best results are obtained when the growth is seeded along the 0 1 0 direction. Minute deviations from this growth direction are found to be detrimental to crystal perfection. The differential thermal analysis shows that the amount of super-cooling required for dissolution and crystallization of KYW in the flux is only 5° and this promotes an easy formation of tiny crystallites in the solution. Consequently, the crystal rotation and the solution cooling rates are found to have pronounced effects on the growth of KYW crystal.