Modified top-seeding solution growing of KTaO3

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

Stoichiometric lithium niobate single crystals with different Li contents have been grown both by the top‐seeded solution growth (TSSG) method from potassium containing flux and by the double crucible Czochralski (DC Cz) method. Spectroscopic properties (e.g. the UV absorption edge, Raman linewidth) and the Curie temperature measurement have been used for the characterization of the crystal composition. The double crucible Czochralski method is found to be suitable for mass production of stoichiometric LiNbO3 with Li content larger than 49.7 mol% and homogeneity of 0.03 mol%. The domain structures and etching morphologies on negative and positive c‐surface were also investigated by chemical etching method. A new domain structure of three‐fold symmetric sectors were observed in near‐stoichiometric LiNbO3 grown by TSSG method. The straight line arrangement hillocks on negative c‐surface and the net‐like arrangement etch lines were observed and explained by stress etching mechanism. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bulk growth, structural and electrical properties of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 piezoelectric single crystals 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.

Effect of the hydrodynamics in high-temperature solutions on the quality of pure and substituted YIG single crystals grown by the TSSG method

Solution growth method of SiC is assumed to be a promising technique to grow high quality SiC bulk crystal. Solution growth of SiC are based on the liquid phase growth from an incongruent melt composed of Si and C. Among various solution growth techniques, top seeded solution growth (TSSG) method for SiC has been widely studied for a next generation SiC growing technique. In TSSG method, the crystal growth on seed crystals is accomplished by the precipitation of solid SiC from C dissolved a Si melt on a seed crystal located at the top of the liquid. Because of the low solubility of C in liquid Si, SiC crystal growth on seed crystals using TSSG involves the use of a Si-rich Si-C solution. Therefore, in the TSSG method, high C solubility is required to increase the growth rate of SiC. Hence, there have been lots of studies how to increase the C solubility of Si melt. Eventually, several metallic solvents were proved to enhance the carbon solubility, so that the growth rate of SiC using TSSG were remarkably increased up to 2 mm/h. So, it is very optimistic to increase the thickness of grown crystal. However, TSSG has critical issue to increase crystal thickness because the C is supplied from the graphite crucible which is also the reservoir of Si melt. As growing time goes, therefore, the crucible will be dissolved to Si melt and the dissolved carbon will be consumed to grow single crystalline SiC crystal. Eventually, the thickness of SiC grown layer will be limited the volume size of graphite crucible. The reduction of graphite crucible will bring about the change of temperature distribution in the solid and liquid inside the reactor. Mechanical failure during crystal growth could be happened. Therefore, in this study, we applied a graphite block inside graphite crucible for elongate the growing time limit using graphite crucible for TSSG. Several graphite blocks with different design and materials properties were evaluated using finite element analysis using COMSOL multiphysics. The simulated results were then applied to the real experimental growth using small seed samples. Finally, the durability of graphite crucible and the crystal quality were comparatively evaluated with and without graphite blocks using several characterizations techniques.

Top Seeded Solution Growth (TSSG) method is assumed to be a promising bulk growth technique for high quality SiC substrate. Generally, the sources of Si and C in the TSSG method are Si chunk and Graphite crucible, respectively. The crystal growth through TSSG method is achieved by the precipitation of solid SiC from C dissolved a Si melt on a seed crystal located at the top of the liquid. The C solubility in pure Si liquid is extremely low, so that metallic solvents such as Cr, Ti and Fe were added to increase the C solubility in Si liquid. Consequently, the growth rate of SiC crystal through the TSSG method has been reached up to 2 mm/hour. However, as increasing C solubility, the loss of the graphite crucible became another critical issue. Because the C source in the TSSG method is the graphite crucible, the reservoir of Si liquid, the increase of C solubility means the decrease of the crucible durability. The graphite crucible durability influences not only on the thickness of the grown crystal, but also on the temperature distribution in the reactor.In this study, we introduce our recent progress on the carbon supply in the TSSG method to produce a reliable long-term growth technique. The interface between graphite crucible and Si liquid was first studied from point of thermodynamics. Considering the reaction between graphite crucible and Si liquid, several crucible structures with different materials and designs were suggested for the improvement of TSSG method based on theoretical understanding.

The top-seeded solution growth (TSSG) method under high oxygen pressure (PO2 ) atmosphere has been developed to obtain large high-performance single crystals of ferroelectric Bi4Ti3O12. Crystals grown at 960 °C at a PO2 of 0.9 MPa exhibited well-saturated hysteresis with a remanent polarization of 48 µC/cm2 and a coercive field of 29 kV/cm. The results of piezoresponse force microscopy indicate that polarization switching is accomplished throughout the crystals. Electric-field-induced strain measurements along the a axis yield a piezoelectric constant d11* of 37 pm/V for Bi4Ti3O12.

The top-seeded solution growth (TSSG) method is an alternative technique for growing SiC which can reduce the defect levels in the crystal.

The top-seeded solution growth (TSSG) method is a critical technique for growing low-defect and high-quality silicon carbide (SiC) single crystals. A comprehensive numerical analysis model including induction heating, heat and mass transfer is developed for growing 6-inch SiC single crystals. The coupling effects of Lorentz force, centrifugal force, thermal buoyancy force and surface tension on the solution flow are considered, and the effects of crystal rotation speed on the velocity field, temperature field, carbon concentration field, crystal growth rate and carbon dissolution and precipitation on the crucible wall are systematically investigated. The results indicate that the Lorentz force in the solution results in a more complex flow field at low crystal rotation speeds. The crystal rotation speed should be controlled within the appropriate range to ensure that the carbon concentration distribution beneath the growth interface determined by the transport mode is coordinated with that at the growth interface determined by the temperature, which is beneficial for the uniform and high growth rate of SiC single crystals. Low rotation speeds reduce the growth rate of SiC single crystals, while high rotation speeds lead radial uniformity of growth rate to decrease. At a rotation speed of 25 r/min, the average growth rate of SiC single crystals is higher and the radial distribution uniformity is better. Further analysis is conducted on the dissolution and precipitation of carbon at the solution-crucible interface, and the regions, where the crucible wall dissolves quickly and SiC polycrystalline particles are generated, are located. The transport directions of polycrystalline particles are predicted based on the velocity field. The research results provide a scientific basis for growing 6-inch SiC single crystals by TSSG method.

A single crystal of ferroelectric 0.88(Bi,Na)TiO3–0.12BaTiO3 (BNT–BT) solid solution with tetragonal P4mm structure was grown by a top-seeded solution growth (TSSG) method at a high oxygen pressure (PO2 ) of 0.9 MPa. The crystals exhibited a large remanent polarization (Pr) of 54 µC/cm2, which leads to a spontaneous polarization estimated to be 54 µC/cm2. The large Pr compared with that of crystals grown at PO2 = 0.1 MPa is suggested to originate from a low oxygen vacancy concentration. The high-PO2 TSSG method is demonstrated to be effective for obtaining large-sized, high-quality BNT–BT crystals.

The top-seeded solution growth (TSSG) method facilitates the production of large-sized silicon carbide (SiC) single crystals with low defect density.

Top-seeded solution growth of Ca-doped YBCO single crystals

Growth and characterization of Na 0.5Bi 0.5TiO 3–BaTiO 3 lead-free piezoelectric crystal by the TSSG method

Growth of CuCl single crystals by the top seeded solution growth method