Top-seeded Solution Growth Method Research Articles

Rational Design via Synergistic Combination Leads to an Outstanding Deep-Ultraviolet Birefringent Li2Na2B2O5 Material with an Unvalued B2O5 Functional Gene.

Birefringent materials, the key components in modulating the polarization of light, are of great importance in optical communication and the laser industry. Limited by their transparency range, few birefringent materials can be practically used in the deep ultraviolet (DUV, λ < 200 nm) region. Different from the traditional BO3- or B3O6-based DUV birefringent crystals, we propose a new functional gene, the B2O5 unit, for designing birefringent materials. Excitingly, the synergistic combination of Li4B2O5 and Na4B2O5 generates a new compound, Li2Na2B2O5, with enhanced optical properties. The Li2Na2B2O5 crystal with a size of up to 35 × 15 × 5 mm3 was grown by the top-seeded solution growth (TSSG) method, and its physicochemical properties were systematically characterized. Li2Na2B2O5 features a large amount of birefringence (0.095@532 nm), a short DUV cutoff edge (181 nm) with a high laser-induced damage threshold (LDT, 7.5 GW/cm2 @1064 nm, 10 ns), favorable anisotropic thermal expansion (αa/αb = 5.6), and the lowest crystal growth temperature (<609 °C) among the commercial birefringent crystals. Moreover, the influences of the B2O5 structural configurations on the optical anisotropy were explored. The fascinating experimental results will provide a prominent DUV birefringent crystal and an effective synthesis strategy, which can facilitate the design of DUV birefringent materials.

Optical spectroscopic study of Ru and Rh doped Bi12TiO20 crystals

Bi12TiO20 (BTO) single crystals in pristine state and doped with ruthenium and rhodium are grown by the top-seeded solution growth method and characterized by optical and Raman spectroscopy. The effect of doping on the vibrational and optical properties is studied. The doped crystals show higher absorption in the visible spectral range and higher transmission in the near infrared region as compared to pristine BTO. The performed spatially resolved polarized Raman measurements reveal no significant doping-induced shift of vibrational modes while differences in the LO/TO intensity ratio of the tetrahedral asymmetric stretching vibration are encountered. The observations are discussed in terms of lattice ordering and dopant oxidation states.

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements.

The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO3) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO3 single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results. There is no melting process in the SSCG method, thus the crystal grown using a SSCG method have inherent higher levels of impurity and defect concentrations, which is a good candidate for investigating the effect of crystal quality on the precursor phenomena. The acoustic, dielectric, and piezoelectric properties, as well as birefringence, of the SSCG-grown BaTiO3 were examined over a wide temperature range. Especially, the acoustic phonon behavior was investigated in terms of Brillouin spectroscopy, which is a complementary technique to Raman spectroscopy. The obtained precursor anomalies of the SSCG-grown BaTiO3 in the cubic phase were similar to those of other single crystals, in particular, of high-quality single crystal grown by top-seeded solution growth method. These results clearly indicate that the observed precursor phenomena are common and intrinsic effect irrespective of the crystal quality.

Growth of high-quality transparent SrB4O7 single crystals with high degradation resistance for DUV laser application

We grew borate crystals, SrB4O7 (SBO), by the top-seeded solution growth (TSSG) method. High-quality transparent SBO single crystals were successfully obtained from the stoichiometric melt by a seed cooling technique. The optical properties of the SBO crystals, which showed wide transparency, high transmittance, and high resistance to optical damage compared with synthetic silica glass and CsLiB6O10 (CLBO) crystals, were evaluated. Our results reveal for the first time that the SBO crystals exhibit outstanding degradation resistance at a DUV wavelength of 266 nm.

Elastic, piezoelectric, and dielectric properties of high-quality KTa0.53Nb0.47O3 single crystal with tetragonal phase

In this study, a large high-quality tetragonal KTa0.53Nb0.47O3 (KTN) single crystal of 18 × 18 × 35 mm3 was grown by the top-seeded solution growth method. The complete sets of elastic, dielectric, and piezoelectric constants for the [001]C-poled KTN single crystal with a macroscopic 4-mm system were confirmed via the combined resonance and pulse-echo ultrasonic methods. The values of the electromechanical coupling factors k33 and kt were 0.690 and 0.618, respectively, similar to those of PZT5A. In addition, the orientation dependence of those properties was calculated via the tensor transformation method, and it was found that the maximum d33 = 132 pC/N, s33E = 9.5 × 10−12 m2/N, and k33 = 0.69 occurred with the new z-axis oriented along [001]C.

Crystal Structure and Judd–Ofelt Analysis of Er3+ Doped LuAl3(BO3)4 Crystal**Supported by the National Natural Science Foundation of China under Grant No 51772171.

Single crystal Er:LuAl3(BO3) (Er:LuAB) is successfully grown using the top-seeded solution growth method with a K2Mo3O10 flux. The cell parameters of the grown crystal are estimated by an x-ray single crystal diffactometor and x-ray powder diffraction analysis. The result indicates that it still belongs to the space group R32. The obtained unit-cell parameters are a = 9.2793(19) Å, c = 7.210(3) Å, V = 537.65(27) Å3, and Z = 3. The absorption spectrum is measured at room temperature. The spectroscopy properties are investigated based on the Judd–Ofelt (J-O) theory, and the effective J-O parameters were calculated to be , , and . The emission spectra of Er:LuAB crystal at room temperature are also studied and the fluorescence around 3170 nm is observed. The emission cross section calculated by the F-L formula is 8.6 × 10−20 cm2. These results suggest that the Er:LuAB crystal may be a promising ∼3 μm laser material.

Flux growth and optical properties of K7CaY2(B5O10)3 nonlinear crystal

Non-centrosymmetric borates K7CaY2(B5O10)3 have been synthesized by solid state reaction and the crystals were successfully grown by the top seeded solution growth method using K2O-B2O3-CaF2 flux. According to the single X-ray diffraction, the structure belongs to the R32 space group with lattice parameters a = 13.2516(2) Å and c = 14.9679(3) Å. IR, Raman, absorption spectra as well as data on melting temperature were obtained for the crystal. The short edge of UV absorption and SHG intensity comparable with KH2PO4 (KDP) suggests that this crystal is a promising nonlinear-optical material.

The Effect of Stepped Wall of the Graphite Crucible in Top Seeded Solution Growth of SiC Crystal

The crucible design having a stepped wall was introduced for increasing the growth rate of SiC crystal without metal addition in top-seeded solution growth (TSSG) method. The numerical simulation confirmed that new crucible design to increase the solvent-crucible interface could definitely change the temperature distribution and increase the carbon concentration. The simulation result, SiC single crystals were grown with Si solvent at 1900°C using a normal crucible and a stepped crucible to investigate the effect of crucible design having a stepped wall. Grown SiC layers were analyzed using Optical microscopy and Raman spectra. The growth rate in the stepped crucible was finally 66um/h observed.

Solution Growth of SiC from the Crucible Bottom with Dipping under Unsaturation State of Carbon in Solvent

SiC crystals are grown using a Si-Cr-based solvent by a top-seeded solution growth (TSSG) method by changing the dipping time after when the growth temperature is reached. Step-flow-like curve morphologies were observed for a dipping time after 15 min, while polycrystallization occurred at the periphery for that after 120 min, which corresponded to the dipping under unsaturated and supersaturated carbon in the solvent, respectively. Furthermore, the solution growth of SiC with dipping under unsaturated carbon was easily realized by the growth from the crucible bottom, step-flow-like growth was achieved. Using this technique, dominant polytypes of SiC in various growth conditions after stable seed dipping under the unsaturation in the solvent can be demonstrated.

Controlled Growth of Layered Acentric CdTeMoO6 Single Crystals with Linear and Nonlinear Optical Properties

Acentric compounds with a layered structure are of current interest owing to their advanced functional properties for technical applications. However, the growth of bulk single crystals of acentric materials with a quasi-two-dimensional structure is challenging, which severely hinders the intrinsic properties investigation and optoelectronic applications of these materials. Herein, we report the controlled growth of bulk CdTeMoO6 single crystals with a layered structure and the investigation of their linear and nonlinear optical properties. High quality CdTeMoO6 single crystals with dimensions of ∼26 × 10 × 9 mm3 were successfully grown through the modified top-seeded solution growth method using TeO2-MoO3 as a flux. The transparent range of CdTeMoO6 single crystals is in the range of 0.345–5.40 μm, and with large birefringence (Δn = no – ne = 0.2868–0.2219 from 514 nm to 1.5467 μm). In addition, the nonlinear optical (NLO) coefficient d36 of CdTeMoO6 single crystals was measured to be 8.5 pm/V using Make...

Effects of the Temperature Gradient Near the Crystal‐Melt Interface in Top Seeded Solution Growth of SiC Crystal

The top seeded solution growth (TSSG) method is a promising technique for fabricating high‐quality silicon carbide (SiC) single crystals. The carbon required to grow SiC is provided by dissolving the graphite crucible in the silicon melt, and the carbon distribution in the silicon melt is governed by various factors. In this study, two hot zone structures are evaluated using the finite element analysis (FEA) simulation, especially for the temperature distribution, the velocity field, and the carbon concentration in the silicon melt. The results of the simulations revealed significant differences between the two hot zone structures in terms of temperature and carbon concentrations, especially near the interface between the crystal and the melt. SiC crystals are experimentally grown to verify the simulation results with the two hot zone structures. The grown crystals are evaluated to study their surface morphology, crystal quality, polytype stability, and dislocation density by using optical microscopy, high‐resolution X‐ray diffraction, micro‐Raman spectroscopy, and chemical etching, respectively. The simulations and experiments suggests that the hot zone structure with a small temperature gradient especially near the interface between the crystal and the melt promotes stable conditions for growing SiC crystals via the TSSG method.

Crystal Growth and Optical Properties of Beryllium-Free Nonlinear Optical Crystal K3Ba3Li2Al4B6O20F

A beryllium-free nonlinear optical (NLO) crystal K3Ba3Li2Al4B6O20F (KBLABF) with sizes up to 18 × 13 × 8 mm3 was successfully grown by the top-seeded solution growth method using LiOH-H3BO3–BaF2 flux. The key limiting factors on the crystal morphologies and sizes were carefully analyzed. Meanwhile, by using the minimum deviation technique, the refractive index dispersion was measured and fitted well by the Sellmeier equations. The results suggest that KBLABF is a negative uniaxial crystal with moderate birefringence of 0.06050–0.06834 at a wavelength range from 363 to 852.1 nm. Furthermore, the type-I phase matching range for fundamental (second harmonic) light is down to 486 (243 nm) in theory, which indicates that KBLABF crystal could achieve 532 and 266 nm light generation by direct second-harmonic generation. As compared with the famous NLO crystals β-BaB2O4 and CsLiB6O10, KBLABF crystal exhibits a smaller walk-off angle and larger acceptance angle at the wavelength of 532 nm while having a comparable...

Thermal, Spectral and Laser Properties of Er3+:Yb3+:GdMgB₅O10: A New Crystal for 1.5 μm Lasers.

A novel laser crystal of Er3+:Yb3+:GdMgB5O10 with dimension of 26 × 16 × 12 mm3 was grown successfully from K2Mo3O10 flux by the top seeded solution growth method. The thermal diffusivity and specific heat capacity were measured to calculate the thermal conductivity of the crystal. The absorption and fluorescence properties of the crystal at room temperature were investigated in detail. The Judd-Ofelt method was used to analyze the polarized absorption spectra. The emission cross-section of the 4I13/2→4I15/2 transition was calculated by the Füchtbauer-Ladenburg formula and the relevant gain cross-sections were estimated. Continuous-wave laser output of 140 mW at 1569 nm with the slope efficiency of 17.8% was demonstrated in a plano-concave resonator. The results reveal that Er3+:Yb3+:GdMgB5O10 crystal is a promising material for 1.5 μm lasers.

Crystal growth, electronic structure and luminescence properties of Nb/Yb co-doped RbTiOPO4 crystals

Nb/Yb co-doped RbTiOPO4 (RTP) crystals were successfully grown by a top-seeded solution growth method from two different kinds of flux systems. 5%Nb/3%Yb: RTP crystal with more transparency was obtained from the mixed solvent containing MoO3. The chemical composition was analyzed by Electron Probe Microanalyzer (EPMA), and the result indicated that co-doping of Nb and Yb into RTP can greatly increase the concentration of Yb in RTP crystal. The addition of MoO3 into self-flux system can improve the quality of as-grown crystals, but it is not helpful to introduce Yb into crystal. The electronic structures of Nb/Yb: RTP crystals were analyzed using X-ray photoelectron spectra (XPS). The results show that the binding energy difference between O 1s and P 2p levels (ΔBE (O-P)) increases firstly with the increase of Yb content, and then decreases with Nb content increasing, which is associated with the covalency change of O-P bonds in crystals. However, the doping has little influence on the chemical bond properties of O-Ti. The FL spectra of Nb/Yb: RbTiOPO4 crystals were also analyzed, and five emission peaks characteristic of Yb3+ ions were observed.

Flux Exploration, Growth, and Optical Spectroscopic Properties of Large Size LaBSiO5 and Eu3+-Substituted LaBSiO5 Crystals

This article reports the flux composition optimization, crystal growth, and optical spectroscopic properties of LaBSiO5 and Eu3+-substituted LaBSiO5 crystals. The mixture design technology was successfully applied in the crystal growth area for the first time. By the direction of mixture design method, the composition of a complex flux comprising LaBO3, SiO2, and Li2MoO4 was optimized and used for growth of LaBSiO5 crystals. A large size of Eu3+-substituted LaBSiO5 crystal with dimension of 12 × 10 × 8 mm3 has been prepared by top-seeded solution growth method. As far as we know, it is the first report that active ion-substituted LaBSiO5 bulk crystal was obtained from an environmentally friendly flux without fluorides. The optical spectroscopy and electronic transition properties of Eu3+-substituted LaBSiO5 crystals are studied thoroughly by analyzing the excitation and emission spectra and luminescence decay curves. The luminescence of Eu3+ ions are characteristic of intense red light emission correspond...

Tetragonal (K, Na)NbO3 based lead-free single crystal: Growth, full tensor properties, and their orientation dependence

A Li and Ta modified (K, Na)NbO3 lead-free single crystal with a large size (13 × 10 × 20 mm3) has been grown by using the top-seeded solution growth method. The large size allows us to carry out an extensive study on this tetragonal crystal. We have measured a complete set of elastic, dielectric, and piezoelectric constants for the [001]C poled crystal with the single domain state. The crystal exhibits high shear piezoelectricity with d15 = 518 pC/N and k15 = 0.733, showing excellent potential in shear electro-sonic energy transformation devices. It is found that the high shear piezoelectricity originates from the vicinity of orthorhombic-tetragonal phase transition, which favors polarization rotation greatly. The orientation dependence of longitudinal dielectric, piezoelectric, and elastic constants and electromechanical coupling factor in the 3-dimentional space were calculated based on the single domain dataset. We believe that this work is of great importance for both fundamental studies and device designs for lead-free materials.

Structural, optical and ferroelectric properties of KNixNb1−xO3 single crystals

Ferroelectric perovskite oxides have attracted considerable attention as photovoltaic materials owing to the bulk photovoltaic effect (BPVE). However, single crystals are necessary to investigate the mechanism underlying the BPVE and bandgap engineering methods are furthermore required in order to increase their optical absorption in the visible region of the solar spectrum. In this study, a high-quality, large-sized (the largest diameter and height were 32 and 29mm, respectively) KNixNb1-xO3 (x = 0.006, 0.010, and 0.012) single crystal was grown using a top-seeded solution growth method. The effect of nickel doping on the optical and ferroelectric properties was investigated. It was observed that while the introduction of nickel induced bandgap narrowing and thus an increase in the visible-light absorption, the concomitant introduction of oxygen vacancies led to slight weakening of the ferroelectric properties. On the whole, however, our results indicate the high potential of KNixNb1-xO3 single crystals for investigating the BPVE and as candidate photovoltaic materials.

Relaxor-based ferroelectric single crystals grown by top-seeded solution growth method

Compared to conventional Pb(Zr1– x Ti x )O3 (PZT) polycrystalline ceramics, relaxor-based (relaxor-PT) ferroelectric single crystals have excellent performance with ultrahigh electromechanical coupling factor and piezoelectric coefficient. For example, the typical relaxor-PT ferroelectric single crystals, such as Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) and Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), have electromechanical coupling factors k 33> 0.9 and piezoelectric coefficients d 33> 2000 pC/N, making them as candidate materials for the next generation of piezoelectric devices, such as piezoelectric transducers, sensors and actuators. But the difficulties for the relaxor-PT single crystals application is the preparation technique. The crystal growth technique, including high-temperature solution (flux) growth, the vertical Bridgman growth and top-seeded solution growth (TSSG) method were used for preparation of relaxor-PT single crystals. TSSG offers some advantages for growth of relaxor-PT single crystals. Therefore, in this article, recent major advances in the development of relaxor-PT single crystals are reviewed in terms of crystal growth using top-seeded solution growth method.

Assessment of growth and spectral properties of Cr3+-doped La0.83Y0.29Sc2.88(BO3)4 crystal

This paper reports the spectral characteristic of Cr3+-doped La0.83Y0.29 Sc2.88 (BO3)4 crystal. Cr3+-doped La0.83Y0.29Sc2.88 (BO3)4 crystal was grown from a flux of Li6B4O9 by the top seeded solution growth method. Cr3+:La0.83Y0.29 Sc2.88 (BO3)4 crystal exhibits broad absorption and emission bands of Cr3+ ions. The absorption cross-section σa is 3.38×10−20cm2 at 467nm and 4.40×10−20cm2 at 656nm for E//c, respectively. The emission band with a peak at 906nmhas a full width at half maximum (FWHM) of 188nm for E//c. The emission cross-section σe at 906nm is 2.35×10−20cm2 for E//c axis and 2.03×10−20cm2 for E⊥c axis. The fluorescence lifetime of 4T2→4A2 transition is 37.7μs. The investigated result indicates that it may be considered as a potential CW tunable laser crystal material.

Lattice Site of Rare-Earth Ions in Stoichiometric Lithium Niobate Probed by OH− Vibrational Spectroscopy

Rare-earth (RE = Er3+, Nd3+, or Yb3+) ion-doped stoichiometric LiNbO3 crystals were grown by the Czochralski and the high-temperature top-seeded solution growth methods. For the 0.22–0.87 mol% concentration range of the RE oxides in the melt/solution, in addition to the well-known hydroxyl (OH−) vibrational band in undoped stoichiometric LiNbO3, a new infrared absorption band was observed at about 3500 cm−1, similar to the case of the trivalent optical damage resistant (ODR) dopants In3+ and Sc3+. By comparing the frequencies and polarization dependences of the bands to those detected for ODR ion containing crystals, they are attributed to the stretching vibration of OH− ions in RE3+Nb-OH− complexes. Consequently, above a given concentration threshold, some of the rare-earth ions are assumed to occupy niobium sites in the LiNbO3 lattice. The same model is also suggested for RE-doped congruent LiNbO3 crystals containing over-threshold (&gt;5 mol %) amounts of the Mg-co-dopant.