YBa_2Cu_3O_<7-x>(Y123) single crystal growth was succeeded by the modified pulling method (Solute Rich Liquid Crystal Pulling method; SRL-CP method). A Y123 single crystal could be pulled as a primary phase from the surface of the BaO-CuO flux melt contained in the Y_2O_3 crucible in which Y_2BaCuO_5 (Y211) solid existed at the bottom as a source of solute. The Y123 crystals had twins but no Y211 inclusion. The growth interface morphology of the crystals consisted of spiral steps, wave-like steps and linearmacro steps. After appropriate oxygen annealing, the temperature dependence of the resistivity of the crystal was measured. Along both the c-axis and the ab-plane, the resistivity showed a metal-like behavior and the superconductive critical temperature was about 89 K with about a 2 K transition width. By controlling the crystal rotationrate according to the change of the crystal diameter with time, a large sized Y123 single crystal was obtained which was 17 mm square and 8 mm in height.
Unstable growth of TiO_2 ribbon and boule single crystals, grown by the edge-defined, film-fed growth (EFG) method, are characterized by periodic change of ribbon width and spiral growth, respectively. Those phenomena occur under the condition that the die top temperature is higher than that at the uniformly shaped crystal growth. Features of this growth are that the temperature distribution on the die top is largely dependent on the location of the growing crystal which absorbs thermal radiation and shields the heat transfer from the die top. In the case of periodic change of ribbon width, higher die top temperature generates meniscus receding and ribbon width decreases. Resultantly, die top temperature is decreased by acceleration of heat radiation from die top. This relation causes the vibration of die top temperature and ribbon width changes periodically. Spiral growth has the same origin as the periodic change of ribbon width. The asymmetric temperature conditions on the die top is maintained by the movement of the meniscus and growing crystal. As a result, the asymmetry persists and a spiral is continuously formed.
This review describes causes of the twisting formation of Gd_3Ga_5O_<12> single crystal during growth in Czochralski method. The force of the natural convection is one of important factors for the twisting formation. We examined the degree of natural convection by changing the positions of an RF coil and constructions of ceramic insulations supporting a crucible. Under the conditions which twisting crystals were obtained, we observed 6℃ of cyclic temperature variation at 30-minute intervals in the melt and anomalous flow patterns on the melt surface. We concluded that unstable melt convection caused asymmetric temperature distribution in the melt.
The relationship between specific properties of BaB_2O_4 supercooling melt and crystallized phases have been investigated by the solidifying experiments of BaB_2O_4 melt using β-BaB_2O_4 single crystal as starting materials. α (high temperature phase), β (low temperature phase) or mixture phase were nudeated from the supercooling melt above 1070℃. BaB_2O_4 supercooling melt transformed into glass like phase at about 1070℃. The glass rapidly crystallized, and α, β or mixture phase were obtained when the cold-finger was touched on the glass surface. α phase preferentially crystallized from glass at 1000-1070℃, then β phase preferentially crystallized from glass below 1000℃. It is suggested that the structure of the glass is similar to BaB_2O_4 crystal structure.
Electric field effects at the interface influence the solute partitioning leading to an electric field-dependent equilibrium solute distribution cocfficient, k_<EO>. The causes of these electric fields, i.e., the thermoelectric power and the charge separation effects (crystallization EMF), are a function of growth velocity, V, temperature gradient, G_L, and solute boundary layer thickness, δ_c. Subsequently, the interface electric field becomes an extremely important variable for the crystallization process. Here, LiNbO_3 crystal growth from a stirred melt is discussed by considering the electric field-dependent solute partitioning for all of the seven intrinsic species. Additionally, the chemical conversion reactions in the melt are taken into account. The above considerations eventually lead us to discuss conditions for the dynamic congruent-state growth of LiNbO_3 from a finite amount of melt, 1-g via the Czochralski technique by finding an appropriate combination of δ_c(g), V(g) and G_L (g).
According to the degree of superheating the "structure" of associated semiconductor melts with covalent-ionic bondings (AII-BM, AIV-BM) may affct the growth stability and crystal quality very sensitively. The supercooling-superheating function of CdTe (PbTe) shows a step-like increase in the degree of supercooling for melts superheated by more than about 10℃. This behavior differs from semiconductor and semimetal melts with covalent-metallic character (Ge, Bi) because of the destruction of high ordered structural complexes existing up to a critical temperature above the melting point. Any reorganization of such structural elements will not occur during reduction of higher superheating. With increasing deviation from stoichiometry the supercooling increases due to the dissolution of the associates by excess solvent. A correlation between the superheating of the melt and the structure of the nucleation region and density of large angle grain boundaries in CdTe and ZnSe Bridgman crystals has been observed.
Semiconductor and oxide crystals for electronic and optical devices are grown from melts Within a thermal and rotating fields. The both fields create melt flow in the melt. The present paper reports three-dimensional structure of molten silicon convection which is observesd by using X-ray radiography method. Additionally, three-dimensional numerical-simulation by using a super computer is also introduced.
Ultrafine particles of tellurium have been produced by the advanced gas-evaporation-method which evaporates tellurium powder from a quartz boat heated by the atmospheric temperature. Particles of 10〜100 nm in size were easily obtained by the present method. The growth condition of hexagonal hollow rod, hexagonal plate, spherical and amorphous particles of tellurium have been determined. Growth and morphology of tellurium ultrafine particles have been discussed on the basis of atmospheric temperature.
Single crystals of copper were grown with the  orientation at a crystal rotation rate varying from O rad・s^<-1> to 4.2 rad・s^<-1> in a strem of purified argon gas by the Czochralski method, and the distribution and density of dislocation in the grown crystals were examined by an etching technique. The following results were obtained. (1) Grown-in dislocations of the order of 10^8/m^2 are dispersedly formed over the cross sections cut along the (111) planes perpendicular to the growth direction of any pulled crystal, while linear arrays of dislocations along <110> direction are also introduced frequently. (2) The distribution of dislocations penetrating the cross sectionsis mainly classified into three types. The type I shows an increases in dislocation density from the crystal center to periphery. The type II has more dislocations at the center of cystal than the type I and shows a nearly homogeneous distribution in the radial direction. The type III shows also a nearly homogeneous radial distribution but the dislocation density is lower than the type II. (3) The average dislocation densities of pulled crystals decreased slightly with an increase of crystal rotation rate.