As-grown Crystal Boule Research Articles

Compositional segregation and electrical properties characterization of [001]- and [011]-oriented co-growth Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal

A Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 relaxor ferroelectric single crystal boule of 3 in. diameter was grown using [001]- and [011]-oriented co-growth crystals as seeds by the modified Bridgman method. The as-grown crystal boule was divided into two growth regions [001] and [011]. The composition and the electrical properties of samples of the two regions were characterized in detail along the growth direction in the whole crystal boule. The PT content of [001]-grown samples increased from 27.7 to 36.8 mol. % along the growth direction, especially they are averagely higher about 0.7 mol. % than those of [011]-grown samples at the same growth position. The PMN content of [001]-grown samples decreased from 43.0 to 34.8 mol. %, which is lower than that of the corresponding [011]-grown samples. The compositional segregation behavior along [001] and [011] growth directions was discussed based on the crystal growth theories. Variations in the rhombohedral to tetragonal phase transition temperature (TRT), the piezoelectric properties, the coercive electric field and the remnant polarization of [001] samples were discussed according to changes in compositional segregation and crystal anisotropy. Under the exact same growth conditions, the [011]-grown crystal has a larger composition segregation effect than that of the [001]-grown crystal. This result provides a positive effect on analysing the nature and reducing the effect of compositional segregation.

Growth and luminescence properties of undoped strontium iodide crystals

High optical quality undoped strontium iodide crystal grown by using the Bridgman method was characterized. Crystal growth process was described and growth technical parameters were discussed. Impurity analysis of raw materials and as-grown crystal boule indicates that it is feasible to pre-purify the raw material by zone refining or recrystallization. Luminescence properties were studied by photoluminescence, radioluminescence, fluorescence decay time, and scintillation time response. As-grown crystal shows good optical transmittance with wavelength concerned and is transparent for its large Stoke shift, 540nm peaked broad emission, which has a fluorescence decay time 494ns at 300K. The broad emission range from 350nm to 800nm was tentatively speculated to be intrinsic and have an origin of self-trapped exciton.

Growth, morphology and anisotropic thermal properties of Nd-doped Sr3Y2(BO3)4 crystal

A high-quality Nd3+:Sr3Y2(BO3)4 laser crystal has been grown by the Czochralski method. The phase purity and accurate unit cell parameters were determined using X-ray powder diffraction; the unit cell parameters are calculated to be a=7.3933 (1)Å, b=15.9461 (2)Å, c=8.6967 (1)Å, and V=1025.29 (5)Å3. Effective segregation coefficients were measured and the optical homogeneity was further characterized by interferometry. A series of possible growth faces (hkl) were also deduced and compared with the as-grown crystal boules using the Bravais–Friedel–Donnay–Harker (BFDH) theory. A full set of thermal properties, including the thermal expansion, thermal diffusivity, specific heat, and thermal conductivity, were measured as a function of temperature. The average linear thermal expansion coefficients along different crystallographic directions were measured to be α11=7.04×10−6K−1, α22=15.32×10−6K−1 and α33=14.35×10−6K−1 over the temperature range 303.15–770.15K. The specific heat was measured to be 0.573Jg−1K−1 (92.64calmol−1K−1) at 330K. The thermal conductivity at room temperature was calculated to be 0.74Wm−1K−1, 1.00Wm−1K−1, and 0.67Wm−1K−1 along the a-, b- and c-axis, respectively. It was found that thermal conductivity increases with increasing temperature, which indicates a glass-like behavior.

X-ray photoelectron spectroscopy, high-resolution X-ray diffraction and refractive index analyses of Ti-doped lithium niobate (Ti:LiNbO3) nonlinear optical single crystal

Congruent LiNbO3 single crystals with Ti ion dopants (2 and 5 mol%) were successfully grown by Czochralski technique in the automatic diameter control facility. As-grown crystal boules were oriented into (0 0 1) direction cut and optically polished for all measurements. Influence of Ti-ion incorporation into LiNbO3 was studied by core level XPS analysis. Powder X-ray diffraction studies were carried out on doped lithium niobate for phase identification. High-resolution X-ray diffraction technique was used to study the crystalline quality through full-width at half-maximum values. The refractive index values are more for doped samples than for pure sample as determined by prism coupling technique with different laser sources.

A New Promising Nonlinear Optical Crystal for Ultraviolet Light Generation: Ca5(BO3)3F

Single crystals of calcium fluoroborate, Ca5(BO3)3F (CBF), have been grown by the flux method with various proportions of LiF. This compound was investigated for nonlinear optical applications and was expected to exhibit an extended transparency window in the ultraviolet. The growth cracking and inclusions in the as-grown crystal boule are discussed. CBF crystallizes in the noncentrosymmetric space group Cm (Z = 2) with a = 8.134(3) A, b = 16.062(5) A, c = 3.5422(9) A and β = 100.88(2)°. The structure is built from [BO3]3− anionic groups and is closely related to the one of calcium oxoborates like YCa4O(BO3)3 (YCOB). The UV absorption edge was measured and compared with the one of YCOB. The refractive indices were measured by the minimum deviation technique and fitted to the Sellmeier equations. The noncritical phase matching (NCPM) wavelengths for harmonic generation are reported.

Growth and properties of Pb[(Zn 1/3Nb 2/3) 0.91Ti 0.09]O 3 single crystals directly from melt

Pb[(Zn 1/3Nb 2/3) 0.91Ti 0.09]O 3 (PZNT91/9) single crystals were grown by a modified Bridgman method directly from melt using an allomeric Pb[(Mg 1/3Nb 2/3) 0.69Ti 0.31]O 3 (PMNT69/31) single crystal as a seed. X-ray diffraction (XRD) measurement confirmed that the as-grown PZNT91/9 single crystals are of pure perovskite structure. Electrical properties and thermal stabilization of PZNT91/9 crystals grown directly from melt exhibit different characters from those of PZNT91/9 crystals grown from flux, although segregation and the variation of chemical composition are not seriously confirmed by X-ray fluorescence analysis (XPS). The [0 0 1]-oriented PZNT91/9 crystals cut from the middle part of the as-grown crystal boules exhibit broad dielectric-response peaks at around 105 °C, accompanied by apparent frequency dispersion. The values of piezoelectric constant d 33, remnant polarization P r, and induced strain are about 1800–2200 pC/N, 38.8 μC/cm 2, and 0.3%, respectively, indicating that the quality of PZNT crystals grown directly from melt can be comparable to those of PZNT91/9 single crystals grown from flux. However, further work deserves attention to improve the dielectric properties of PZNT crystals grown directly from melt. Such unusual characterizations of dielectric properties of PZNT crystals grown directly from melt are considered as correlating with defects, microinhomogeneities, and polar regions.

Optical, electrical, and X-ray-structural studies on Verneuil-grown SrTiO 3 single crystal: Annealing study

In order to clarify crystal defect effects on the physical phenomena observed for a SrTiO 3 single crystal grown by Verneuil method, the optical density and photoluminescence spectra, complex impedance spectra, and crystal structure were fully studied for the as-grown crystal boule. The as-grown crystal boule consists of a shell (which is colorless transparent and electrically good insulator) and a core (which is dark blue and has a high electrical conductivity (>10 –3 Ω –1cm –1), and a colossal static dielectric constant (>10 6) at room temperature). The as-grown single crystal was then annealed at 973 K in an Ar–H 2 gas stream. With the progressing of annealing, the as-grown single crystal becomes colorless-transparent insulator and the static dielectric constant decreases down to approximately 300 at room temperature. The X-ray crystallographic studies indicate that the crystallinity is almost independent of the annealing, while the dielectric property is considerably affected by the annealing. A model on the basis of a (Ti 3+–oxygen vacancy) complex defect is proposed for explaining the observed properties of SrTiO 3.

Large-aperture YCOB crystal growth for frequency conversion in the high average power laser system

Yttrium calcium oxyborate YCa 4O(BO 3) 3 (YCOB) is a novel non-linear optical crystal possessing good thermal, mechanical and non-linear optical properties. Large-aperture YCOB crystals with 75 mm diameter were grown for high-average power frequency conversion on the mercury laser system. The growth morphology (included facet and spiral growth), cracking and inclusions in the as-grown crystal boule were discussed as the critical problem for large-aperture YCOB crystal growth. This can be minimized through modification of the growth program, including pulling rate, separation procedure, and cooling program. High-average power frequency conversion of the mercury laser using YCOB has been demonstrated, and experimental validation of YCOB material yields 50% conversion at 10 Hz has been achieved.

Growth and characterization of Sr 3TaGa 3Si 2O 14 crystal

Sr 3TaGa 3Si 2O 14 (STGS) crystal boules were grown by the Czochralski method using Z-, Y- and X-axis seed, respectively. Crystal growth experimental results show that a perfect crystal could be grown by using the X-axis seed, and the as-grown crystal boule is transparent with free inclusion and no crack. The X-ray powder diffraction (XRPD) analysis shows that the structure of STGS crystal is the same as that of La 3Ga 5SiO 14 (LGS) crystal. The XRPD pattern was calculated and indexed by using the program TREOR. The segregation coefficients of Sr 3+, Ta 5+, Ga 3+ and Si 4+ ions in crystal growth were measured by using the X-ray fluorescent analysis method, and the results show that the chemical compositions of the as-grown STGS crystals are consistent with their raw materials. The special heat, the thermal expansion and the transmission spectrum of STGS have been measured too, and the results show STGS possesses better thermal properties and transmittance than LGS. The test result on the Q-switch properties indicates STGS has poor electrooptic effect and may not be used as a Q-switch.

Crystal growth of PbTiO3 by the top-seeded solution-growth method

Centimeter-size crystals of lead titanate PbTiO3 have been grown by the top-seeded solution-growth (TSSG) method using two different solvents: PbO and a mixture of PbO and B2O3. The maximum dimensions of the as-grown crystal boules were 32 × 32 × 6 mm3. The PbO-rich side of the phase diagram of the PbO-TiO2 system has been derived by means of crystal-growth experiments. If there is more than 11 mol% of TiO2 in the PbO-TiO2 solution, single crystal of PbTiO3 are obtained. If there is 5–9 mol% or less than 4 mol%, PbO in the tetragonal or orthorhombic phase is formed, respectively.

ＢａＴｉＯ３単結晶の作製とその諸特性

Photorefractive BaTio3 single crystal were successfully prepared by a combination of Top-Seeded Solution Growth technigue and suitable poling processes. The single crystals were grown from the melt which was the mixture of TiO2/BaCO3=65/35 in molar ratio. The employed sources of TiO2 and BaCO3 were 99.99% and 99.999% purity powders, respectively. The asgrown crystal boules, the dimensions of about 20x 20x 15mm3, were cut into 3-5mm rectangular prisms. Subsequently, the crystals were polished, and domain walls of those were removed by applying uniaxal compressive stress and electrical field.The obtained crystals, whose phase transitions were clearly observed at about 130°C by DSC measurement, exhibited typical ferroelectricity. And furthermore, self-pumped phase conjugation was observed in the single domain BaTiO3 crystals by using an argon ion laser operating at 515nm.