A heater comprises a plurality of zones with at least two zones having a variable power density gradient different from one another. The heater having zones of different variable power density gradients allows for controlling the heat output and temperature profile of the heater in one or more directions of the heater. The heater can be used, for example, to control the temperature profile in a vertical direction.

An indium phosphide single crystal including a straight body portion having a cylindrical shape, wherein a residual strain in a tangential direction in an outer circumferential portion is a compressive strain, the outer circumferential portion extending between an inner circumferential surface located 10 mm inward from an outer circumferential surface of the straight body portion toward a central axis and a location located 5 mm inward from the outer circumferential surface. There is also provided an indium phosphide single crystal substrate, wherein a residual strain in a tangential direction in an outer circumferential portion is a compressive strain, the outer circumferential portion extending between an inner circumference located 10 mm inward from an outer circumference toward a center and a location located 5 mm inward from the outer circumference.

A gallium arsenide single crystal including a straight body portion having a cylindrical shape, wherein a residual strain in a tangential direction in an outer circumferential portion is a compressive strain, the outer circumferential portion extending between an inner circumferential surface located 10 mm inward from an outer circumferential surface of the straight body portion toward a central axis and a location located 5 mm inward from the outer circumferential surface. There is a gallium arsenide single crystal substrate, wherein a residual strain in a tangential direction in an outer circumferential portion is a compressive strain, the outer circumferential portion extending between an inner circumference located 10 mm inward from an outer circumference toward a center and a location located 5 mm inward from the outer circumference.

Methods and wafers for vertical gradient freeze 8 inch gallium arsenide (GaAs) substrates. In disclosed examples, vertical gradient freeze systems for forming gallium arsenide (GaAs) substrates having silicon as a dopant, the system includes a crucible to contain a GaAs liquid melt and seed material during a formation process; one or more heating coils arranged in a plurality of heating zones; and a pedestal to move relative to the crucible, the system operable to control heating of the plurality of heating zones and movement of the pedestal to form a single crystal GaAs substrate.

Methods are provided that include depositing a nickel-base superalloy powder including gamma nickel solid solution and gamma prime (Ni.sub.3Al) solid solution phases onto a seed crystal having a predetermined primary orientation, fully melting the powder and a portion of the seed crystal at a superliquidus temperature to form an initial layer having the predetermined primary orientation, heat treating the layer at subsolvus temperatures to precipitate gamma prime solid solution phase particles, depositing additional powder over the layer, melting the deposited powder and a portion of the initial layer at a superliquidus temperature to form a successive layer having the predetermined primary orientation, heat treating the layer at a subsolvus temperature to precipitate gamma prime solid solution phase particles, and repeating depositing additional powder, melting the additional powder and the portion of the successive layer at the superliquidus temperature, and heat treating the successive layer at a subsolvus temperature.

An induction furnace assembly comprising a chamber having a mold; a primary inductive coil coupled to the chamber; a layered susceptor comprising at least two layers of magnetic field attenuating material surrounding the chamber between the primary inductive coil and the mold to nullify the electromagnetic field in the hot zone of the furnace chamber.

A process for directional solidification of a cast part comprises energizing a primary inductive coil coupled to a chamber having a mold containing a material; energizing a primary inductive coil within the chamber to heat the mold via radiation from a susceptor, wherein the resultant electromagnetic field partially leaks through the susceptor coupled to the chamber between the primary inductive coil and the mold; determining a magnetic flux profile of the electromagnetic field; sensing a magnetic flux leakage past the susceptor within the chamber; generating a control field from a secondary compensation coil coupled to the chamber, wherein the control field controls the magnetic flux experienced by the cast part; and casting the material within the mold under the controlled degree of flux leakage.

A single-crystal turbine blade and a method of making such single-crystal turbine blade are disclosed. During manufacturing, a secondary crystallographic orientation of the material of the single-crystal turbine blade is controlled based on a parameter of a root fillet between an airfoil of the single-crystal turbine blade and a platform of the single-crystal turbine blade. The parameter can be a location of peak stress in the root fillet expected during use of the turbine blade.

The present invention relates to the purification of silicon. The present invention provides a method for purification of silicon. The method includes recrystallizing starting material-silicon from a molten solvent comprising aluminum to provide final recrystallized-silicon crystals. The method also includes washing the final recrystallized-silicon crystals with an aqueous acid solution to provide a final acid-washed-silicon. The method also includes directionally solidifying the final acid-washed-silicon to provide final directionally solidified-silicon crystals.

A semi-insulating gallium arsenide crystal substrate has a main surface with a plane orientation of (100) and a diameter of 2R mm, the main surface having a specific resistance with an average value of 510.sup.7 .Math.cm or more and with a standard deviation divided by the average value of the specific resistance, or with a coefficient of variation, of 0.50 or less in each of three measurement areas having their centers at distances of 0 mm, 0.5R mm, and (R-17) mm, respectively, from the center of the main surface in the [010] direction.