Apparatus for manufacturing scintillator and manufacturing method thereof

Abstract

Disclosed herein is an apparatus for manufacturing a single crystal, the apparatus comprising: a furnace comprising a furnace wall; the quartz tube is concentrically arranged in the furnace wall; the induction coil is arranged in an annular part between the quartz tube and the furnace wall; the crucible is arranged on the bottom surface of the furnace in the quartz tube; wherein the crucible comprises a wall extending upwardly from a bottom crucible surface; the refractory lining is arranged in the annular part between the quartz tube and the crucible; wherein a portion of the refractory liner has a different composition, property, geometry, or combination thereof than the remainder of the crucible.

Description

Technical Field

[0001] This disclosure relates to an apparatus for manufacturing a scintillator and a method for manufacturing the apparatus. In particular, this disclosure relates to a furnace for crystal growth that reduces impurities bound in the crystal lattice during a high-temperature oxide crystal growth process. The crystal is used in positron emission tomography (PET) scintillation detectors. Background Technology

[0002] In the manufacture of high-temperature oxide crystals (such as those from lutetium orthosilicate (LSO), lutetium-yttrium silicate (LYSO), gadolinium aluminum gallium garnet (GAGG), etc.), powders in appropriate stoichiometric ratios are contained in a crucible and heated to form a melt. The melt is then brought into contact with a seed crystal, which is gradually extracted from the melt to form a crystal.

[0003] During the process of manufacturing a single crystal, it is desirable for dopants in the melt to be uniformly distributed, resulting in a uniform distribution within the crystal bole. However, this is usually not the case. Dopants tend to migrate to the surface of the melt and accumulate in the center of the crystal bole. It is also desirable for impurities not to bind within the bole. However, this is usually not the case.

[0004] Due to the geometric symmetry of the furnace and the resulting thermal field, the convective flow of the melt creates a cold spot at the center of the crucible, thus creating a location where impurities can be collected. The symmetrical flow field within the furnace, due to its geometric symmetry, results in convective flow of the melt with a cold spot at the center. Since the seed crystal contacts the melt at the center (i.e., at the cold spot), impurities tend to become incorporated into the blank. Therefore, a method is needed to minimize the impurity concentration at the center of the crystal blank during single crystal formation.

[0005] The desired outcome is to generate a flow field in the crucible that moves impurities away from the location where the seed crystal contacts the melt. Summary of the Invention

[0006] This document discloses an apparatus for manufacturing single crystals, the apparatus comprising: a furnace including a furnace wall; a quartz tube concentrically disposed within the furnace wall; an induction coil disposed in an annular portion between the quartz tube and the furnace wall; a crucible disposed at the bottom surface of the furnace within the quartz tube; wherein the crucible includes a wall extending upward from the bottom surface of the crucible; and a refractory lining disposed in an annular portion between the quartz tube and the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the remainder of the crucible.

[0007] This paper discloses a method for growing single crystals, comprising: placing a crucible in a furnace; wherein the crucible contains a melt operable to produce a single crystal; a refractory liner is placed in the furnace and surrounds the crucible; wherein a portion of the refractory liner has a different composition, properties, geometry, or combination thereof from the rest of the crucible; heating the melt within the crucible, wherein the different composition, properties, geometry, or combination thereof generates a thermal gradient within the melt to pull the cold point of the convection unit of the melt away from the seed position in the crucible; and pulling a crystal blank from the seed position in the crucible to grow a single crystal.

[0008] This document also discloses high-purity crystal blanks comprising lutetium orthosilicate, lutetium-yttrium orthosilicate, gadolinium gallium garnet, or gadolinium aluminum gallium garnet, wherein the crystal blanks are prepared by a method comprising: placing a crucible in a furnace; wherein the crucible contains a melt operable to produce crystal blanks of lutetium orthosilicate, lutetium-yttrium orthosilicate, gadolinium gallium garnet, or gadolinium aluminum gallium garnet; placing a refractory lining in the furnace and surrounding the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the rest of the crucible; heating the melt within the crucible, wherein the different composition, properties, geometry, or combination thereof creates a thermal gradient within the melt to pull the cold point of the convection unit of the melt away from the seed position in the crucible; and pulling the crystal blank from the seed position in the crucible. Attached Figure Description

[0009] Figure 1 This is an exemplary depiction of a furnace, in which a crucible is arranged within the furnace; Figure 2 This is an exemplary depiction of the flow field of the melt in the crucible; Figure 3 This is an exemplary top view depicting the refractory lining around the crucible, which causes the cold spot in the melt to shift from the center of the crucible to an off-center position; Figure 4A This is another exemplary top-view depiction of the refractory lining surrounding the crucible, which causes the cold spot in the melt to shift from the center of the crucible to an off-center position; and Figure 4B It is an exemplary side view depiction of a refractory lining disposed around a crucible; wherein the refractory lining has holes that facilitate the movement of cold spots in the melt to an off-center position. Detailed Implementation

[0010] The invention can be more readily understood by referring to the following detailed description of preferred embodiments of the invention and the examples included therein. Unless explicitly stated otherwise, all numerical values ​​herein are assumed to be modified by the term "approximately". The term "approximately" generally refers to a range of numbers that a person skilled in the art would consider equivalent to the listed numerical values ​​(i.e., having the same function or result). In many examples, the term "approximately" may include numbers rounded to the nearest significant digit.

[0011] This paper discloses a method for producing a crystal blank with reduced amounts of impurities. The paper also discloses a crystal blank containing a lower percentage of impurities than blanks produced by other methods. During the production of the crystal blank, an induction coil at a symmetrical position in the furnace (around the crucible) generates a symmetrical thermal field in the melt (contained in the crucible). This symmetrical thermal field leads to the formation of symmetrical convective flow in the melt, which in turn results in the formation of a cold spot at the center of the melt. The cold spot contains a higher percentage of undesirable impurities than the surrounding melt. These impurities are incorporated into the crystal blank as the pull rod contacts the cold spot during its production. In other words, the formation of the centrally located cold spot promotes impurity migration to the center of the blank. This leads to the concentration of impurities in the crystal blank as the seed crystal contacts the melt at the cold spot to create a nucleation point.

[0012] This situation can be mitigated by altering the thermal symmetry of the furnace, which in turn creates an asymmetric flow field in the crucible. This causes impurities to concentrate in the melt at a point located far from the point where the seed crystal contacts the melt. The method disclosed herein promotes dopant migration to a preferentially eccentric region of the blank by creating convection paths within the blank. This is achieved by creating thermal paths in a circular refractory liner placed between the crucible and a quartz tube located inside the induction coil. Therefore, cold spots can be moved away from the center toward the crucible wall, and, if desired, can be created even further away from the center and closer to the crucible wall. By moving the cold spots, impurities will not be located at the point where the seed crystal contacts the melt, and therefore will not be incorporated into the crystal blank.

[0013] Figure 1 This is a side view of a furnace 100 (in which the blank is grown) in an illustrative embodiment. The furnace 100 includes a furnace wall 102 enclosing a space 104. A copper coil 106 is wound around the outer surface of the furnace wall 102. Water or coolant flows through the copper coil 106 to remove heat from the furnace 100 or maintain the temperature in the space 104 within the furnace 100. A quartz tube 108 is concentrically disposed within the furnace wall 102. An induction coil 110 is disposed in an annular portion between the quartz tube 108 and the furnace wall 102. A crucible 114 is placed at the bottom surface 116 of the furnace 100 within the quartz tube 108. The crucible 114 includes a cylindrical wall extending upward from the bottom crucible surface. The crucible 114 may be made of iridium. The crucible 114 extends upward from the bottom surface 116 as a portion of the furnace 100. A brick or ceramic refractory cylinder 115 extends from the top of the crucible 114 to the top of the furnace 100 or the cover 130. A refractory lining 118 is provided in the annular portion 128 between the quartz tube 108 and the crucible 114 / brick cylinder 115.

[0014] To create a blank, the raw material for forming melt 120 is placed in crucible 114, and crucible 114 is concentrically placed within furnace 100. Induction coil 110 is activated to heat the raw material, thereby forming melt 120. Seed crystal 122 is lowered at the end of rod 124 through brick cylinder 115 to contact the top of melt 120 at the seed position (i.e., the position where the blank is to be pulled out of the melt). Seed crystal 122 is then pulled upward from melt 120, allowing melt 120 to cool and crystallize around seed crystal 122. While the seed crystal is rotating simultaneously, pulling seed crystal 122 upward produces a blank or cylindrical crystal.

[0015] Figure 2 A side view 200 of a crucible during melt heating is shown. When the melt is heated above a given temperature, convection units 202 are formed in the melt 120. Heat at the wall 204 of the crucible 114 causes the melt 120 to flow upward at the wall 204. Upon reaching the top of the crucible 114, the melt 120 migrates radially inward toward the central axis 206 of the crucible 114, thereby cooling in the process. A cold spot 215 is thus formed at the top of the melt at the central axis 206. Impurities will tend to collect at the cold spot 215. The melt 120 then descends along the central axis 206 to the bottom of the crucible 114. The method disclosed herein generates a thermal gradient in the melt to move the cold spot 215 away from the central axis 206.

[0016] Figure 3 Figure 4 illustrates a method for moving the cold spot 215 away from the central axis 206. This method involves altering the material composition, material properties, geometry, or a combination thereof of at least a portion of the refractory lining 118 surrounding the crucible 114. The change in thermal conductivity can be achieved by altering the cross-sectional geometry, thermal properties, or chemical composition of a portion of the refractory lining 118 compared to the rest of the refractory lining, or even by removing a portion of the lining. This alteration in the refractory lining transforms a symmetric thermal field into an asymmetric thermal field, causing the cold spot to move from the center of the crucible to a point closer to the crucible wall.

[0017] In this embodiment, different compositions, properties, geometries, or combinations thereof create a thermal gradient within the melt to pull the cold spots of the melt's convection units away from the seed position in the crucible. A crystal blank is then pulled from the crucible's usual seed position (located at the center) to grow a single crystal.

[0018] The portion of the refractory lining that differs from the rest of the refractory lining can be 2% to 25% of the total volume of the refractory lining, preferably 5% to 15%.

[0019] In one embodiment, the method includes changing the material composition of one or more portions of the refractory liner 118 compared to the rest of the refractory liner. In another embodiment, the method includes changing the geometry of a portion of the refractory liner 118 compared to the rest of the refractory liner. All of these embodiments are discussed in detail below.

[0020] For the sake of simplicity, Figure 3 , Figure 4A and Figure 4B These ideas are depicted by showing only a portion of the furnace. Figure 3 Only the crucible 114 containing the melt 120 and the refractory lining 118 surrounding the crucible 114 are depicted. The refractory lining 118 is uniform in nature or geometry and surrounds the crucible and the induction coil. Figure 3 , Figure 4A and Figure 4B When the furnace (not shown) is symmetrically arranged, the cold spot occurs at the central axis 206 of the crucible 114 (and therefore the melt 120). This is because the distribution of heat in the furnace (not shown) is symmetrical. The symmetrical thermal field in the melt 120 (and in the crucible 114) causes the cold spot to be centrally located at the central axis 206.

[0021] exist Figure 3 In the embodiment depicted, the refractory liner 118 includes four quadrants 118A, 118B, 118C, and 118D. Each of these quadrants may have a positioning element (not shown) that allows them to be assembled within the annular portion 128 surrounding the crucible 114 (see [link to documentation]). Figure 2 A concentric tubular insulating layer is formed within the structure. In an embodiment, one of the four quadrants may be made of a material having a different thermal conductivity than the other quadrants. Figure 3 Quadrant 118B is depicted, comprising a material having a different thermal conductivity than quadrants 118A, 118C, and 118D. Quadrant 118B comprises a first material having a first thermal conductivity, while quadrants 118A, 118C, and 118D each comprise a second material having a second thermal conductivity, wherein the second thermal conductivity differs from the first thermal conductivity. It should be noted that although the refractory lining 118 has been described in terms of the fractional units comprising the quadrants, other fractional units such as one-half, one-third, one-fifth, one-sixth, etc., can be used to form the entire refractory lining.

[0022] The first and second materials are different from each other, but are selected from the group consisting of alumina, zirconium oxide, yttrium-stabilized zirconium oxide (YSZ), graphite, silicon dioxide, magnesium oxide, lime, silicon carbide, tungsten carbide, boron nitride, hafnium carbide, molybdenum disilicide, tantalum hafnium carbide, or combinations thereof. Alumina and zirconium oxide are preferred refractory materials.

[0023] In one embodiment, quadrant 118B may include alumina, while quadrants 118A, 118C, and 118D each include zirconium oxide. In another embodiment, quadrant 118B may include zirconium oxide, while quadrants 118A, 118C, and 118D each include alumina. Using a quadrant comprising a material different from the other quadrants helps to facilitate cold spot movement away from the central axis 206.

[0024] Using a quadrant (or part) with a material composition different from the other quadrants (or parts) results in a shift of the cold point 215 towards the eccentric position 406. This is because the different thermal conductivity of quadrant 118B compared to the other quadrants 118A, 118C, or 118D causes an asymmetric thermal field in crucible 114, which causes the cold point 215 to migrate from the central axis 206 (a concentric position with respect to crucible 114) to the eccentric position 406 (an eccentric position with respect to crucible 114) and is circumscribed by the dashed ellipse 308.

[0025] When the seed crystal at the end of the pull rod is immersed into the melt at the center of the melt (which is located along the central axis 206), it no longer contacts the cold spot (because the cold spot has moved to the off-center position 406), and impurities that are usually bound to the crystal blank are no longer bound to the blank.

[0026] In another embodiment, even if the material composition is the same as the other parts of the refractory lining, the cold spot can be moved from the central axis 206 to an off-center position by making one part of the refractory lining have different thermal conductivity characteristics. For example, refer to Figure 3 All quadrants 118A, 118B, 118C, and 118D can comprise the same material (e.g., zirconium oxide or alumina). However, quadrant 118B can have a different porosity than quadrants 118A, 118C, and 118D. In other words, the packing density of quadrant 118B can differ from that of quadrants 118A, 118C, and 118D. This difference in porosity contributes to thermal asymmetry in crucible 114, causing the cold point to migrate from the central axis 206 (relative to the concentric position of crucible 114) to an eccentric position 406 (relative to the eccentric position of crucible 114).

[0027] Therefore, selecting a portion of the refractory lining that differs from the others (either in composition or physical properties) can facilitate the movement of the cold spot from the center to an off-center location, thus minimizing the binding of impurities into the crystal blank.

[0028] A portion of the refractory lining may have a different geometry than the rest of the refractory lining. Differences in geometry can include changes in size, the shape of the cross-sectional area, or combinations thereof. Changes in cross-sectional area include differences in the shape of the cross-section taken from a portion of the refractory lining, either in a horizontal or vertical plane.

[0029] As in Figure 3 As seen, each quadrant 118A, 118B, 118C, and 118D has a radial thickness d1. In an embodiment, one of the quadrants (such as, for example, 118B) may have a radial thickness d1 that is smaller than the radial thickness d2 of each of the remaining quadrants 118A, 118C, and 118D. This is in Figure 3 The thickness of one quadrant is not depicted, but can be readily conceived by those skilled in the art. This difference in thickness within one quadrant results in an asymmetric thermal field, which in turn promotes any asymmetry in the melt flow field within the crucible and causes cold spots to be closer to the crucible wall than to the center.

[0030] In another embodiment, Figure 4A and Figure 4B As depicted, holes 302 or 304 are provided in the refractory liner 118. Holes can be drilled into the refractory liner after it has been manufactured. Alternatively, the refractory liner can be cast or molded during casting or molding with the holes formed. Holes 302 or 304 are radially oriented and extend from the inner surface to the outer surface through the thickness of the refractory liner 118. As mentioned above, the refractory liner 118 is located in an annular portion 128, which is situated between the quartz tube 108 and the crucible 114. The presence of holes 302 and 304 in the refractory liner alters the symmetry of the thermal field surrounding the crucible 114 and facilitates a change in the thermal symmetry of the melt 112.

[0031] Thermal paths are created by providing holes in the refractory lining, through which heat generated by the crucible can be dissipated. The holes are asymmetrical in some ways or others, which in turn creates an asymmetrical flow field. The portion of the crucible adjacent to the holes is cooler than the surrounding portion. This creates a convection path (also known as a cold finger) for the molten material contained within the crystal blank.

[0032] Holes or grooves 302 can be formed in any of the four quadrants to cause a change in the symmetry of the thermal field in the furnace. By creating one or more holes in one or more quadrants of the refractory lining, a deviation can be created in the thermal field of the melt (and therefore in the flow field). This deviation can be caused as long as the holes created in the refractory lining are not symmetrically distributed around the central axis 206.

[0033] For example, refer to Figure 4AA single hole 302 can be created in quadrant 118B of the refractory lining. The presence of the hole will cause an asymmetry in the thermal field of the melt and cause the cold spot to shift from the central axis 206 (of the crucible) to a new position 406 closer to the quadrant 118b with the hole 302 (and circumscribed by the dashed ellipse 308). The hole 302 can be a partial or complete hole, but its presence causes an alteration in the heat distribution around the crucible. The heat distribution changes from symmetrical to asymmetrical, thus causing the cold spot to move to an off-center position relative to the center of the crucible (central axis 206). The cold spot is no longer concentric with respect to the geometry of the crucible, the refractory lining, or the furnace.

[0034] More than one hole can be provided in the refractory lining. For example, as in Figure 4A As seen, the first hole 302 can be located in quadrant 118B, while the second hole 304 (whose dimensions differ from those of the first hole 302) can be located in quadrant 118D. Multiple holes can be located in one or more quadrants of the refractory lining, and as long as the holes are asymmetrically distributed around the crucible, these holes will facilitate the movement of cold spots to off-center positions. For example, more holes can exist in the refractory lining on one side of the crucible compared to the other side. Alternatively, the holes in the refractory lining on one side can be larger than one or more holes on the other side.

[0035] Figure 4B Another embodiment of the refractory liner is described, which includes multiple holes to create a cold finger that promotes cold spot displacement. Figure 4B A side view of crucible 114 is depicted, in which a refractory lining 118 is disposed around crucible 114. One portion of the refractory lining may contain a plurality of holes 302A, 302B, 302C, etc. from top to bottom to generate a heat finger that promotes the movement of the cold spot from the center (located along the central axis 206) to an off-center position.

[0036] Because the cold spot is moved to an off-center position, the seed crystal no longer contacts the cold spot when the crystal blank is extracted. In short, asymmetry can be created by adjusting the holes in the refractory liner to move the center of the flow field away from the geometric center of the blank. The cold spot can be moved away from the center towards the wall, and if desired, it can be formed at the wall of the crucible. Impurities are removed from the center to prevent them from combining during seed crystal nucleation and are removed from the crystal blank. By moving the cold spot, impurities will not be located at the seed crystal.

[0037] In the embodiments, the methods disclosed herein can be used to produce single-crystal blanks containing a small percentage of impurities, such as lutetium orthosilicate (LSO), lutetium-yttrium orthosilicate (LYSO), gadolinium gallium garnet (GGG), and gadolinium aluminum gallium garnet (GAGG). The purity of the single-crystal blank is greater than 99%, preferably greater than 99.5%, and more preferably greater than 99.9%.

[0038] In this embodiment, pixels obtained from the center of the crystal blank have a much lower impurity content than pixels obtained from the outer surface of the crystal blank. The crystal blank is divided into a plurality of pixels, and crystal blanks produced by the aforementioned method typically produce pixels with fewer impurities when positioned at the center of the blank than when positioned at the outer surface of the blank. In other words, there exists a purity gradient from the center of the blank to the outer surface of the blank, wherein the center has a smaller amount of impurities than the surface.

[0039] In embodiments, an asymmetric melt field is used in the furnace based on how much cerium and other desired co-dopersant binds to the lattice, resulting in a reduction of impurities in the crystal blank. When an asymmetric flow field is used, a change in the crystal's scintillation characteristics is observed, indicating that less cerium and other desired co-dopersant absorption is bound to the crystal blank. This leads to the understanding that if cerium and other desired co-dopersant are driven to the outside of the melt's center by using an asymmetric flow field, impurities in the melt can then be removed by bringing the melt into contact with the seed crystal at a location away from the cold spot. Using this invention in production processes, it is desirable to increase the concentration of useful co-dopersant (e.g., cerium) in the original mixture of the melt's chemical composition to compensate for the reduced absorption of these desired co-dopersant.

[0040] While the invention has been described with reference to some embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for its elements without departing from the scope of the invention. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from the basic scope of the invention. Therefore, it is contemplated that the invention is not limited to the specific embodiments disclosed as the best mode for carrying out the invention, but rather that the invention will include all embodiments falling within the scope of the appended claims. Claims (as amended under Article 19 of the Treaty) 1. An apparatus for manufacturing single crystals, comprising: Furnace, including furnace walls; Quartz tubes, which are concentrically arranged inside the furnace wall; An induction coil is disposed in an annular portion between the quartz tube and the furnace wall; A crucible disposed at the bottom surface of the furnace within the quartz tube; wherein the crucible includes a wall extending upward from the bottom surface of the crucible; and A refractory lining is disposed in an annular portion between the quartz tube and the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the remainder of the crucible. 2. The apparatus of claim 1, wherein the remainder of the refractory lining has a uniform and consistent composition, properties or geometry throughout its volume. 3. The apparatus of claim 1, wherein a portion of the refractory lining comprises 2% to 25% of the total volume of the refractory lining. 4. The apparatus according to claim 1, wherein the refractory lining comprises alumina, zirconium oxide, yttrium oxide-stabilized zirconium oxide, graphite, silicon dioxide, magnesium oxide, lime, silicon carbide, tungsten carbide, boron nitride, hafnium carbide, molybdenum disilicide, tantalum hafnium carbide, or a combination thereof. 5. The apparatus of claim 1, wherein a portion of the refractory lining comprises alumina, and wherein the remainder of the refractory lining comprises zirconium oxide. 6. The apparatus of claim 1, wherein a portion of the refractory lining comprises zirconium oxide, and wherein the remainder of the refractory lining comprises alumina. 7. The apparatus of claim 1, wherein the different properties include differences in packing density. 8. The apparatus of claim 1, wherein the different properties include differences in porosity. 9. The apparatus of claim 1, wherein the different geometries include having different shapes in the cross-sectional area. 10. The apparatus of claim 1, wherein the different geometries include having different cross-sectional thicknesses measured in the radial direction. 11. The apparatus of claim 1, wherein the different geometries include having one or more holes in at least a portion of the refractory lining; wherein at least one hole extends radially through the refractory lining. 12. The apparatus of claim 1, wherein the different geometries include having a plurality of holes in at least two portions of the refractory lining; and wherein the plurality of holes in one portion of the refractory lining are different in size from the holes in the other portion of the refractory lining. 13. A method for growing a single crystal, comprising: A crucible is placed inside a furnace; wherein the crucible contains a melt operable to produce a single crystal; A refractory lining disposed in the furnace and surrounding the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the remainder of the crucible; Heating the melt within the crucible, wherein the different compositions, properties, geometries, or combinations thereof generate a thermal gradient within the melt to pull the cold points of the convection units of the melt away from the seed crystal positions within the crucible; and A crystal blank is pulled out from the seed position of the crucible to grow the single crystal. 14. The method of claim 13, further comprising providing holes in at least a portion of the refractory lining to produce the different geometries. 15. The method of claim 14, wherein the remainder of the refractory lining has a uniform and consistent composition, properties or geometry throughout its volume. 16. The method of claim 14, wherein a portion of the refractory lining comprises alumina, and wherein the remainder of the refractory lining comprises zirconium oxide, or vice versa. 17. The method of claim 14, wherein the different geometries include having different shapes in the cross-sectional area. 18. The method of claim 14, wherein the different geometries include having one or more holes in at least a portion of the refractory lining; wherein at least one hole extends radially through the refractory lining. 19. A high-purity crystal blank, comprising: Lutene orthosilicate, yttrium orthosilicate, gadolinium gallium garnet, or gadolinium aluminum gallium garnet, wherein the crystal blank is prepared by a method comprising the following: A crucible is placed inside a furnace; wherein the crucible contains a melt operable to produce crystal blanks of lutetium orthosilicate, lutetium yttrium orthosilicate, gadolinium gallium garnet, and gadolinium aluminum gallium garnet; A refractory lining is placed in the furnace and surrounds the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the rest of the crucible; The melt within the crucible is heated, wherein the different compositions, properties, geometries, or combinations thereof generate a thermal gradient within the melt to pull the cold points of the convection units of the melt away from the seed crystal positions within the crucible; and The crystal blank is pulled out from the seed position in the crucible. 20. The crystal blank according to claim 19, wherein the seed crystal in the crucible is located at the center of the melt in the crucible.

Claims

1. An apparatus for manufacturing single crystals, comprising: Furnace, including furnace walls; Quartz tubes, which are concentrically arranged inside the furnace wall; An induction coil is disposed in an annular portion between the quartz tube and the furnace wall; A crucible disposed at the bottom surface of the furnace within the quartz tube; wherein the crucible includes a wall extending upward from the bottom surface of the crucible; and A refractory lining is disposed in an annular portion between the quartz tube and the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the remainder of the crucible.

2. The apparatus according to claim 1, wherein, The remainder of the refractory lining has a uniform and consistent composition, properties, or geometry throughout its volume.

3. The apparatus according to claim 1, wherein, A portion of the refractory lining comprises 2% to 25% of the total volume of the refractory lining.

4. The apparatus according to claim 1, wherein, The refractory lining comprises alumina, zirconium oxide, yttrium-stabilized zirconium oxide, graphite, silicon dioxide, magnesium oxide, lime, silicon carbide, tungsten carbide, boron nitride, hafnium carbide, molybdenum disilicide, tantalum hafnium carbide, or combinations thereof.

5. The apparatus according to claim 1, wherein, A portion of the refractory lining comprises alumina, and the remainder of the refractory lining comprises zirconium oxide.

6. The apparatus according to claim 1, wherein, A portion of the refractory lining comprises zirconium oxide, and the remainder of the refractory lining comprises aluminum oxide.

7. The apparatus according to claim 1, wherein, The different properties include differences in packing density.

8. The apparatus according to claim 1, wherein, The different properties include differences in porosity.

9. The apparatus according to claim 1, wherein, The different geometries include those with different shapes in the cross-sectional area.

10. The apparatus according to claim 1, wherein, The different geometries include having different cross-sectional thicknesses measured in the radial direction.

11. The apparatus according to claim 1, wherein, The different geometries include having one or more holes in at least a portion of the refractory lining; wherein at least one hole extends radially through the refractory lining.

12. The apparatus according to claim 1, wherein, The different geometries include having a plurality of holes in at least two portions of the refractory lining; and wherein the plurality of holes in one portion of the refractory lining are of different sizes than the holes in the other portion of the refractory lining.

13. A method for growing a single crystal, comprising: A crucible is placed inside a furnace; wherein the crucible contains a melt operable to produce a single crystal; A refractory lining disposed in the furnace and surrounding the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the remainder of the crucible; Heating the melt within the crucible, wherein the different compositions, properties, geometries, or combinations thereof generate a thermal gradient within the melt to pull the cold points of the convection units of the melt away from the seed crystal positions within the crucible; and A crystal blank is pulled out from the seed position of the crucible to grow the single crystal.

14. The method of claim 13, further comprising providing holes in at least a portion of the refractory lining to produce the different geometries.

15. The method according to claim 14, wherein, The remainder of the refractory lining has a uniform and consistent composition, properties, or geometry throughout its volume.

16. The method of claim 14, wherein, A portion of the refractory lining comprises alumina, and the remainder of the refractory lining comprises zirconium oxide, or vice versa.

17. The method of claim 14, wherein, The different geometries include those with different shapes in the cross-sectional area.

18. The method according to claim 14, wherein, The different geometries include having one or more holes in at least a portion of the refractory lining; wherein at least one hole extends radially through the refractory lining.

19. A high-purity crystal blank, comprising: Lutene orthosilicate, yttrium orthosilicate, gadolinium gallium garnet, or gadolinium aluminum gallium garnet, among which, The crystal blank is prepared by a method comprising the following: A crucible is placed inside a furnace; wherein the crucible contains a melt operable to produce crystal blanks of lutetium orthosilicate, lutetium yttrium orthosilicate, gadolinium gallium garnet, and gadolinium aluminum gallium garnet; A refractory lining is placed in the furnace and surrounds the crucible; wherein a portion of the refractory lining has a different composition, properties, geometry, or combination thereof from the rest of the crucible; The melt within the crucible is heated, wherein the different compositions, properties, geometries, or combinations thereof generate a thermal gradient within the melt to pull the cold points of the convection units of the melt away from the seed crystal positions within the crucible; and The crystal blank is pulled out from the seed position in the crucible.

20. The crystal blank according to claim 19, wherein, The seed crystal in the crucible is located at the center of the melt in the crucible.

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