The present disclosure provides a method for manufacturing a Nd:YAG single crystal fiber exhibiting a radial concentration distribution where the Nd concentration reaches a maximum at a central axis of the single crystal fiber. The method for manufacturing a Nd:YAG single crystal fiber according to the present disclosure involves: preparing a source material having a rod shape and containing a YAG single crystal or polycrystal, Nd, and Ca; melting an end of the source material to form a molten zone; and bringing the molten zone into contact with a seed crystal and pulling up the seed crystal to grow the single crystal fiber.

A single crystal manufacturing apparatus to grow a single crystal upward from a seed crystal, the apparatus including an insulated space thermally insulated from a space outside the single crystal manufacturing apparatus, an induction heating coil placed outside the insulated space, a thermal insulation plate that divides the insulated space into a first space including a crystal growth region to grow the single crystal and a second space above the first space and includes a hole above the crystal growth region, a heating element that is placed in the second space and generates heat by induction heating using the induction heating coil to heat the inside of the insulated space, and a support shaft to vertically movably support the seed crystal from below.

In the present invention, once a polycrystalline silicon rod is grown by the Siemens process, the polycrystalline silicon rod is heat-treated within a temperature range from 750 C. to 900 C. to relieve residual stress in the crystal. According to the experiment of the present inventors, residual stress can be relieved satisfactorily by heat treatment at the above-described low temperature, and in addition, metal contamination cannot be induced and the physical properties of the polycrystalline silicon rod cannot be changed. The above heat treatment can be conducted inside a furnace used to grow the polycrystalline silicon rod, and can also be conducted outside a furnace used to grow the polycrystalline silicon rod. According to the present invention, a polycrystalline silicon rod with residual stress () of not more than +20 MPa evaluated by a 2-sin.sup.2 diagram can be obtained.

In the present invention, once a polycrystalline silicon rod is grown by the Siemens process, the polycrystalline silicon rod is heat-treated within a temperature range from 750 C. to 900 C. to relieve residual stress in the crystal. According to the experiment of the present inventors, residual stress can be relieved satisfactorily by heat treatment at the above-described low temperature, and in addition, metal contamination cannot be induced and the physical properties of the polycrystalline silicon rod cannot be changed. The above heat treatment can be conducted inside a furnace used to grow the polycrystalline silicon rod, and can also be conducted outside a furnace used to grow the polycrystalline silicon rod. According to the present invention, a polycrystalline silicon rod with residual stress () of not more than +20 MPa evaluated by a 2-sin.sup.2 diagram can be obtained.

A method for manufacturing monocrystalline sapphire directly in bar form, the method comprising the following steps of: providing a crucible (100), the crucible having a sapphire piece forming a seed for sapphire growth; placing the crucible (100) in an enclosure (4) under vacuum or a controlled atmosphere and heating the enclosure (4) to bring the crucible up to operating temperature; feeding the crucible with raw material (M) via a feed system (3) to form molten raw material (F) in the crucible; gradually solidify the molten raw material and gradually form a sapphire bar (C); interrupting the feed of raw material (M) and completely crystallising the molten material (F) remaining in the crucible; cooling the crucible to ambient temperature; recovering the sapphire bar bonded to the resulting seed, the seed and/or a portion of the bar, after being sawn, being able to form both a new back and a new seed.

A method for manufacturing monocrystalline sapphire directly in bar form, the method comprising the following steps of: providing a crucible (100), the crucible having a sapphire piece forming a seed for sapphire growth; placing the crucible (100) in an enclosure (4) under vacuum or a controlled atmosphere and heating the enclosure (4) to bring the crucible up to operating temperature; feeding the crucible with raw material (M) via a feed system (3) to form molten raw material (F) in the crucible; gradually solidify the molten raw material and gradually form a sapphire bar (C); interrupting the feed of raw material (M) and completely crystallising the molten material (F) remaining in the crucible; cooling the crucible to ambient temperature; recovering the sapphire bar bonded to the resulting seed, the seed and/or a portion of the bar, after being sawn, being able to form both a new back and a new seed.

An inorganic structure having mechanical properties that differ depending on the region in the inorganic structure, and a method for manufacturing the inorganic structure are provided. An inorganic structure (1) of the present embodiment includes a plurality of solidified portions (SA) composed of an inorganic material. The plurality of solidified portions (SA) include a first solidified portion (SA1) having a first crystallographic direction (CO1) preferentially oriented in a predetermined direction, and a second solidified portion (SA2) having a second crystallographic direction (CO2) that is a different orientation from the first crystallographic direction (CO1).

An inorganic structure having mechanical properties that differ depending on the region in the inorganic structure, and a method for manufacturing the inorganic structure are provided. An inorganic structure (1) of the present embodiment includes a plurality of solidified portions (SA) composed of an inorganic material. The plurality of solidified portions (SA) include a first solidified portion (SA1) having a first crystallographic direction (CO1) preferentially oriented in a predetermined direction, and a second solidified portion (SA2) having a second crystallographic direction (CO2) that is a different orientation from the first crystallographic direction (CO1).