An alumina substrate on which an AlN layer is formed and that causes less warping, and a substrate material strong enough to withstand normal handling when an AlN crystal is grown upon it, and prevents cracking and fracturing of a grown crystal when stress is applied during growing or cooling. The substrate has a gap and a rare earth element-containing region inside the AlN layer or at the interface between the AlN layer and the alumina substrate. Warping of the AlN layer can be reduced by lattice-mismatch stress being concentrated at the region and releasing of stress by the gap. The region having a concentrating of stress, and the gap having a low mechanical strength, can induce crackings and fracturings. As a result, contamination of crackings and fracturings into the crystal grown on the substrate can be prevented. The region can ensure a level of mechanical strength sufficient for handling.

Various metal oxide mesocrystals can be synthesized in a simple manner by a method for producing a metal oxide mesocrystal, the method comprising the step of annealing an aqueous precursor solution comprising one or more metal oxide precursors, an ammonium salt, a surfactant, and water at 300 to 600 C. Composite mesocrystals consisting of a plurality of metal oxides or an alloy oxide can also be provided.

Various metal oxide mesocrystals can be synthesized in a simple manner by a method for producing a metal oxide mesocrystal, the method comprising the step of annealing an aqueous precursor solution comprising one or more metal oxide precursors, an ammonium salt, a surfactant, and water at 300 to 600 C. Composite mesocrystals consisting of a plurality of metal oxides or an alloy oxide can also be provided.

An alumina substrate wherein an AlN layer is formed on a surface of the alumina substrate and a rare earth elements-containing layer and/or rare earth elements-containing regions is/are formed in the interior of the AlN layer or in the interface between the AlN layer and the alumina substrate.

An alumina substrate wherein an AlN layer is formed on a surface of the alumina substrate and a rare earth elements-containing layer and/or rare earth elements-containing regions is/are formed in the interior of the AlN layer or in the interface between the AlN layer and the alumina substrate.

Provided is a method for producing an n-type SiC single crystal, whereby it is possible to grow an n-type SiC single crystal having a low resistivity at a high speed. A method for producing an n-type SiC single crystal by bringing a SiC seed crystal substrate into contact with a SiC solution having such a temperature gradient that the temperature gradually decreases from the inside toward the surface, thereby achieving the crystal growth of the n-type SiC single crystal. The method involves adding a nitride to a raw material for forming the SiC solution or to the SiC solution.

Provided is a method for producing an n-type SiC single crystal, whereby it is possible to grow an n-type SiC single crystal having a low resistivity at a high speed. A method for producing an n-type SiC single crystal by bringing a SiC seed crystal substrate into contact with a SiC solution having such a temperature gradient that the temperature gradually decreases from the inside toward the surface, thereby achieving the crystal growth of the n-type SiC single crystal. The method involves adding a nitride to a raw material for forming the SiC solution or to the SiC solution.

A region of an SiC solution in the vicinity of an SiC seed crystal is cooled while suppressing the temperature variation in a peripheral region of the SiC solution. An apparatus includes a seed shaft and a crucible for an SiC solution. The seed shaft has a lower end surface for attachment to an SiC seed crystal. The crucible comprises a main body, an intermediate cover, and a top cover. The main body includes a first cylindrical portion and a bottom portion at a lower end portion of the first cylindrical portion. The intermediate cover is within the first cylindrical portion and above the liquid level of the SiC solution in the main body. The intermediate cover has a first through hole for the seed shaft. The top cover is disposed above the intermediate cover and has a second through hole for the seed shaft to pass through.

A region of an SiC solution in the vicinity of an SiC seed crystal is cooled while suppressing the temperature variation in a peripheral region of the SiC solution. An apparatus includes a seed shaft and a crucible for an SiC solution. The seed shaft has a lower end surface for attachment to an SiC seed crystal. The crucible comprises a main body, an intermediate cover, and a top cover. The main body includes a first cylindrical portion and a bottom portion at a lower end portion of the first cylindrical portion. The intermediate cover is within the first cylindrical portion and above the liquid level of the SiC solution in the main body. The intermediate cover has a first through hole for the seed shaft. The top cover is disposed above the intermediate cover and has a second through hole for the seed shaft to pass through.

Scanning Laser Epitaxy (SLE) is a layer-by-layer additive manufacturing process that allows for the fabrication of three-dimensional objects with specified microstructure through the controlled melting and re-solidification of a metal powders placed atop a base substrate. SLE can be used to repair single crystal (SX) turbine airfoils, for example, as well as the manufacture functionally graded turbine components. The SLE process is capable of creating equiaxed, directionally solidified, and SX structures. Real-time feedback control schemes based upon an offline model can be used both to create specified defect free microstructures and to improve the repeatability of the process. Control schemes can be used based upon temperature data feedback provided at high frame rate by a thermal imaging camera as well as a melt-pool viewing video microscope. A real-time control scheme can deliver the capability of creating engine ready net shape turbine components from raw powder material.