Top Seeded Solution Growth Technique Research Articles

P-doping growth of photorefractive Bi 12TiO 20 single crystals

Photorefractive cubic sillenite Bi 12TiO 20 single crystals doped with P were successfully grown by using the top-seeded solution growth technique with a novel double-crucible configuration. P-doping growth with a double-crucible resulted in a distinct habit modification and striation-free crystals. P-doping increased optical rotatory power and showed a blue-shift of optical absorption edge. A phase diagram of the Bi 2O 3BiPO 4 binary system was also investigated with regard to obtaining Bi 12PO 20 crystals with a sillenite structure.

The effect of variation of thermal field on the morphology of β-BaB2O4 single crystals grown by top-seeded solution growth

The construction of a furnace for the growth of single crystals from high temperature solutions, giving a varying temperature distribution in the solution over a wide range, is described. This furnace has been used for growing β-BaB2O4 (BBO) single crystals by the top-seeded solution growth (TSSG) technique without pulling. A correlation has been found between the shape of the crystals obtained and the nature of the isotherms in the solution. It is shown that by choosing a suitable temperature distribution in the solution it is possible to obtain growth conditions of BBO crystals with a thickness commensurable with their diameter.

Influence of Ta doping on the growth and superconducting properties of YBa 2Cu 3O 6 + δ crystals

Single crystals of YBa 2Cu 3O 6 + δ, completely separated from flux, measuring up to 5–6 mm 2 and 0.25–0.5 mm thick, were grown reproducibly from BaCuO 2 solutions containing 0.8 wt% Ta 2O 5, by the top seeded solution growth technique. Addition of Ta increases the crystal size due to reduced nucleation. The crystals exhibit a broad superconducting transition at 80 K when annealed in air (a narrow transition at 86 K on oxygen annealing), attributed to the incorporation of stoichiometric excess of oxygen in the presence of Ta, as supported by the EDX, thermogravimetry and oxygen titration analysis.

Growth of oxygen deficiency-free YVO 4 single crystal by top-seeded solution growth technique

In spite of its excellent properties, yttrium orthovanadate (YVO 4) laser host single crystal has not been successfully adopted into high-tech applications because of crystal growth difficulties in connection with oxygen loss. This work is the first to apply a top-seeded solution growth (TSSG) technique to YVO 4, by which oxygen deficiency-free crystals can be directly grown. Since undesirable non-pentavalent vanadium oxides are continuously forming during the YVO 4, growth process, the flux media, in addition to the conventional TSSG requirements, must prevent the formation of oxygen deficient yttrium vanadate crystals. From these multiple requirements, lithium metavanadate (LiVO 3) was selected as the best solvent for YVO 4 flux growth. LiVO 3 has suitable solubility for YVO 4, low viscosity, low vaporization without toxicity (in the 1200–1400°C working temperature range), and the oxygen deficient Li-V bronze (γ-LiV 2O 5) can easily form in it, thus preventing oxygen defect formation in the yttrium vanadate crystals. Wanklyn's model and Viting and Timofeeva's calculation data were applied successfully for preliminary selection of the flux material. From the schematic V 2O 5-Li 2O-V 2O 3 ternary and Y 2O 3-V 2O 5-Li 2O-V 2O 3 quaternary systems, the phase relations of Li-V bronzes and YVO 4 can be resolved much more easily than from the previous simple binary systems. The transparent, macro-defect-free single crystal sample grown by the TSSG technique illustrates the significance of these considerations and the promise of this growth technology for YVO 4 crystals.

Growth of large pure, doped and co-doped La2CuO4 single crystals

La 2 CuO 4 single crystals doped with Sr, Ba, Nd and Zn as well as co-doped Sr, Nd have been grown by the top-seeded solution growth technique. In very low gradients, crystals of very good quality could be grown up to 3 cm 3 but had small amounts of flux inclusions. Higher thermal gradients have produced high quality, large area, crack-free crystals. Crystals were grown along the tetragonal (100) and (001) directions in low as well as larger thermal gradients

Photorefractive effect of BaTiO_3 single crystals grown in inert atmospheres

BaTiO3 single crystals were grown by the top-seeded solution growth technique in inert atmospheres of nitrogen gas and of argon gas and in air. They were then annealed at 1200°C in air. These crystals, prepared from a mixture of 99.999% pure BaCO3 powder and 99.99% pure TiO2 powder, contained virtually equal amounts of transition-metal impurities (Fe, Co, Ni, etc.). The maximum beam-coupling gain of the two crystals grown in inert atmospheres was 6 cm−1, and that of the crystal grown in air was 3 cm−1; the sign of the beam-coupling gain of the crystals was positive. We found that the crystals grown in inert atmospheres exhibited high gains without having been doped with any transition-metal elements.

Growth of KTiOPO 4 (KTP) single crystals by means of phosphate and phosphate/sulfate fluxes out of a three-zone furnace

Large single crystals of KTiOPO 4 were grown with the top seeded solution growth technique out of a three-zone furnace. As a flux, K 6P 4O 13 and { xK 6P 4O 13: yK 2SO 4} were used. Sulfate containing fluxes reduce the growth temperature by more than 60°C. Crystal pulling modifies the habit of the as-grown crystals. The area around the seed gets relatively smaller, while the {210}/{011} growth sectors pointing downwards into the flux get relatively larger. Excellent temperature control and proper seed orientation are necessary to avoid inclusion formation. Different characterization methods confirm the high quality of the grown KTP crystals.

Growth of garnets for optical isolators by top-seeded solution growth method

A method to grow garnets with high specific rotation for optical isolators is proposed. The method utilizes the top-seeded solution growth technique. Relatively large and homogeneous Gd3−xBixFe5O12 single crystals, which are nearly free from flux inclusions, have been grown from a high-temperature solution of Bi2O3. The crystal grown is found to have low transmission losses (0.018 dB for 45° Faraday rotation) with high extinction ratios (≥40 dB) at 1.3- and 1.5-μm wavelength regions. Some basic characteristics of the garnet are also given.

Growth of single crystals of pure and Ce-doped Nd 2CuO 4

Single crystals of Nd 2CuO 4 have been grown from excess CuO by a top seeded solution growth technique. Ce-doped Nd 2CuO 4 platelet-like single crystals have also been grown by slow cooling of the melt with nucleation sites provided by a platinum wire.

Phase diagram and single crystal growth of pure and Sr doped La 2CuO 4

Single crystals of pure and Sr doped La 2CuO 4 have been grown from excess CuO with a top seeded solution growth technique. Crystals have been grown both in air and in oxygen. Growth in air leads to an oxygen deficiency as evidenced by a reduction in the lattice parameters. Differential Thermal Analysis measurements in oxygen on this system reveal a eutectic temperature of 1075°C for the composition 87.5 mol% CuO. Measurements in air show a reduction in the eutectic temperature to 1040°C and the formation of a 3 component system with the partial reduction of CuO to Cu 2O.

Top seeded solution growth of La 4CuO 4

Single crystals of La 2CuO 4 have been grown from a flux with a top seeded solution growth technique. X-ray and chemical analyses indicate the presence of some flux impurities that are detrimental to superconductive properties. Strontium addition was also attempted to produce superconductive crystals.

Top Seeded Solution Growth of Lanthanum Copper Oxide

ABSTRACTSingle crystals of pure and Sr doped La2CuO4 have been grown with a top seeded solution growth technique. Crystals grown from a lithium borate flux incorporate impurities detrimental to superconductive properties while those grown from excess copper oxide are free from this difficulty.

Stockbarger crystal growth, optical assessment and laser performance of holmium-doped yttrium erbium lithium fluoride

The Stockbarger technique is demonstrated to be capable of producing Ho 3+ doped yttrium erbium lithium fluoride single crystals with a high degree of optical homogeneity and an absence of light scattering centres in the visible region of the electromagnetic spectrum. The laser performance of relatively heavily doped material is showm to compare favourably with equivalent material grown by the top seeded solution growth technique.

The growth of single crystal calcite by top-seeded solution growth technique

Optically clear single crystals of calcite up to 2 cm in length have been pulled from a Li 2CO 3 flux in the range of 50–75 wt% CaCO 3 under a pressure of 1–15 atm of carbon dioxide. The necessary phase equilibria for this growth was experimentally verified. The best growth parameters were a pull rate of 0.25 mm/hr with a rotation rate of 28 rpm. Seed orientation and perfection are critically important.

Measurements of solution properties and the growth of single crystals of lead tantalate PbTa 2O 6

The solubility of lead tantalate, PbTa 2O 6, a ferroelectric tungsten bronze, has been measured for a number of solvents. The best was found to be Pb 2V 2O 7 and the density, viscosity, and heat capacity of this solution was measured together with the diffusivity of lead tantalate in that solvent. Single crystals of lead tantalate with dimensions 2×2×5 mm were grown by the top seeded solution growth technique and the crystal size obtained was found to correlate with that predicted by a simple hydrodynamic theory.

Top-seeded solution growth of oxide crystals from non-stoichiometric melts

A top-seeded solution growth technique for the production of strain-free crystals of oxides from nonstoichiometric melts has been developed. The method has been applied to obtain crystals of ferro-electrics where melt growth of the pure material is not feasible. It has also been extended to more complex melts for the growth of complex germanate laser host crystals. The growth technique, being essentially isothermal, is suitable for use where very high quality crystals are necessary and controlled size and shape are required in contrast to the usual flux methods.