Crystal Growth Applications Research Articles

Low frequency vibrational stirring: A new method for rapidly mixing solutions and melts during growth

A new method for rapidly stirring liquids has been developed which may be useful in crystal growth applications. The method involves the introduction of orthogonally coupled low frequency vibrations to fluids contained in cylindrical crucibles. A mathematical model has been developed to describe the influence of this vibrational stirring method on fluid flow. The optimum sloshing frequencies calculated for a specific system geometry were very close to those observed experimentally. A systematic study of the fluid flow induced by the vibrational motion was carried out at room temperature using aqueous solutions containing glycerine. Preliminary experiments were carried out to study the effect of vibrational stirring on interface shape and position during the Bridgman growth of CsCdCl3, a model system.

Growth and holography application of Fe-doped LiNbO 3 single crystals

Single crystal growth and holography application of Fe-LiNbO 3 were investigated. The Fe-LiNbO 3 crystals were grown from the melt of congruent composition along the c-axis by the Czochralski technique. Its maximum defraction efficiency was greater than 80%; besides a write-in Fourier transform hologram, a reflection hologram was also successfully recorded in the crystal. The hologram for nondestructive testing and heat-motion field display showed quite good results. In our experiment, a He-Ne laser could also be used to record the hologram.

Tetramethoxysilane as gel forming agent in crystal growth

Tetramethoxysilane as gel forming agent in crystal growth leads to alkali-free growth media, makes it possible to work in purely alcoholic solution and can be easily used for growing fully or partially deuterated crystals. The alcohol formed during gel formation limits its use in the presence of oxidizing agents. Some chemical aspects of gelling are discussed and examples of the application in crystal growth are given.

Phase relations in the system Fe2O3B2O3 and its application in single crystal growth of FeBO3

A study of the phase relations in the system Fe2O3B2O3 to aid in finding the optimum conditions to grow single crystals of iron borate was made. The compositions of the system Fe2O3B2O3 studied were with 20, 30, 40, 50, 60, 70 and 80 mole% of Fe2O3, at temperatures of 670, 800, 860 and 900°C. At all compositions and at low temperatures (670−800°C), FeBO3 is the prevalent stable phase. FeBO3 is stable up to 800°C for 0.25 ≤ Fe2O3/B2O3 ≤ 2.6. At 750°C and for 1 ≤ Fe2O3/B2O3 ≤ 2.6, two phases are present, FeBO3 and Fe3BO6. When Fe2O3/B2O3 > 2.6, FeBO3 disappears and Fe3BO6 and α-Fe2O3 are found. Thus, FeBO3 is obtained at low temperatures and with an excess of B2O3. Single crystals of borate FeBO3 with maximum dimensions of up to 8 mm are obtained from the flux with a mixture containing 1 Fe2O35 B2O31 Bi2O3. To avoid the formation of α-Fe2O3 and Fe3BO6, the mixture was cooled rapidly between 1135 and 860°C.

Diffusivities of ammonium and potassium alums in aqueous solutions

AbstractDiffusivities of ammonium and potassium alum solutions have been measured by an interferometric technique. Values are recorded for the diffusion of solutions of different concentration into water at 25°, and of solutions containing 2 g. of hydrate/100 g. of water diffusing into water at temperatures within the range 20 to 40°. Measurements have also been made for diffusion between near‐saturated solutions, and these values are considered suitable for application in crystal growth and dissolution studies. The activation energy for diffusion in near‐saturated solutions (20 to 40°) is approximately 2.8 kcal./mole.Viscosity and density measurements have been made over the temperature range 15–50° and at solution concentrations up to saturation. Solubility data have also been checked over the same temperature range.