JPH04338191A - Production of single crystal - Google Patents

Abstract

PURPOSE:To easily and stably obtain single crystal by passing the sintered rod for a raw material through the inside of an infrared convergent band melting furnace at high speed and making the sintered rod uniform and dense and thereafter passing the same through the inside of the furnace at low speed and crystallizing it in the case of using the melting furnace and growing single crystal in a band melting method. CONSTITUTION:MgO and Al2O3 are mixed with oxides of lanthanoid elements at such a ratio that single crystal having composition of LnMgAl11O19 (Ln shows lanthanoid elements of La, Ce, Pr, Nd, Sm, Eu, Gd and solid solution thereof) is obtained. The sintered rod for a raw material is produced by forming this mixture and heat-treating the formed body. Then this sintered rod is melted in an infrared convergent band melting furnace equipped with the halogen lamps 4, a quartz pipe 3 and a rotary ellipsoidal mirror 5 or the like. This melt is once passed through a zone at 30-70mm/h speed and the uniform and dense raw material rod M is produced. Then the obtained raw material rod M is again melted in the furnace. While this melt is brought into contact with a seed crystal S, it is passed through the zone at 1-4mm/h. Single crystal of LnMgAl11O19 is grown by a band melting method.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to LnMgAl11O19
The present invention relates to a method for growing a single crystal using a zone melting method, by once melting a sintered rod, which is a raw material, in a relatively short period of time and subjecting it to a zone pass.

0002

[Prior Art] LnMgAl11O19 single crystal has properties such as high thermal conductivity, chemical stability, and high solid solubility of optically active species such as Nd in rare earth positions, and is therefore a high-power laser oscillation material. It is an industrial material that is expected to be used as a material. Unlike the Bridgman method and the pulling method, single crystal growth using the band melting method allows crystal growth without using a crucible, and can be grown relatively quickly, so it can be used for semiconductor crystals and optical devices that do not want to be contaminated with impurities. It has been performed on crystals and magnetic crystals.

0003

When a single crystal is grown by the zone melting method, a raw material rod that is uniform in composition and diameter, and is dense and straight is used as the raw material. Conventionally, when manufacturing a sintered rod of LnMgAl11O19, the melting point of the compound was as high as 1950°C, so
It is difficult to obtain a dense sintered body using normal sintering methods, and when growing a single crystal, it is difficult to maintain the zone due to the permeation effect of the porous sintered body, making crystal growth stable. It was difficult to do so.

An object of the present invention is to provide a method for producing uniform and dense growth raw materials in a relatively short time and for easily and stably growing LnMgAl11O19 single crystals.

[0005]

[Means for Solving the Problems] In order to achieve the above object, in the method for producing a single crystal according to the present invention, an infrared convergence zone melting furnace is used, and LnMgAl11O is produced by a zone melting method.
19 Single crystal manufacturing method for growing single crystals (However, L
n represents each lanthanide element La, Ce, Pr, Nd, Sm, Eu, Gd and their solid solution), and the sintered rod serving as the raw material is melted in an infrared condensing zone melting furnace. ,
A uniform and dense raw material rod is created by once zone passing at a speed of 30 mm/h to 70 mm/h, and the obtained raw material rod is melted again in an infrared condensing zone melting furnace to form a 1 mm/h
A single crystal is formed by zone pass at a speed of 4 mm/h.

[0006]

[Operation] When LnMgAl11O19 single crystal is produced using the zone melting method, a dense raw material rod with a uniform composition is required as the raw material. Conventionally, when creating a raw material rod, the usual solid phase sintering method was used, but LnMgAl11
Since O19 has a high melting point of about 1950° C., it is difficult to perform dense sintering, and it is difficult to perform stable zone pass. This is because when using a porous raw material, the melt in the zone permeates into the raw material rod due to the difference in permeability of the porous raw material, resulting in the raw material rod swelling or, in severe cases, cracking and falling. .

[0007] When using a raw material rod that is insufficiently sintered, the raw material vaporizes or scatters violently during growth and contaminates the furnace tube, making crystal growth difficult. Furthermore, if the composition of the raw material rod is not uniform, the composition of the zone will vary, making crystal growth difficult. However, these problems do not occur if the zone is moved faster than the speed at which the melt in the zone permeates into the raw material rod, and even when using porous raw materials, it is possible to stably perform zone passes in a short time. can.

The rod thus produced is a polycrystalline substance, but since it is once melted and then resolidified, it is completely dense and has excellent uniformity in its composition. When growing using the molten raw material, the zone is stably maintained for the reasons mentioned above, and it is easy to perform another zone pass at 1 mm/h to 4 mm/h to monocrystallize the raw material. . By using the zone movement speed within this range, even a relatively poorly dense sintered rod can be stably zone-passed, and by using the resulting molten raw material,
Single crystal growth can be easily performed.

[0009]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

(Example 1) Lanthanum neodymium magnesium aluminate (La0.9Nd0.1MgAl11
In O19), the raw material powder was synthesized by a conventional solid phase reaction method. That is, after sufficiently mixing a predetermined amount of La2O3, MgO, and Al2O3 with a ball mill, the predetermined temperature (12
The reaction was carried out by reacting at 00°C for 10 hours or more. The degree of reaction of the obtained reaction product was examined by powder X-ray diffraction, but sufficient reaction did not occur and the X-ray diffraction pattern was similar to that of the mixed powder.

After pulverizing the obtained raw material powder again using a ball mill to make the particle size fine and uniform,
One side sealed, thickness 8mm, length 150mm, thickness 0
．． 1-2 ton/c using a 2mm natural rubber bag
A press molded body having a uniform length of 130 mm was obtained by hydrostatic pressing of m2. The density of the press-formed body was determined from the external shape and mass and was 2.6 g/cm3. This amounts to 60% of the ideal density of the sample. When performing a hydrostatic press, the bag is filled and excess air is removed using a vacuum pump, and then placed on top of a halved pipe with an inner diameter of 8 mm and fixed with adhesive tape to create a pressed body with less bending. I was able to get it.

[0012] The obtained press-formed body is held by a platinum wire in a vertical electric furnace maintained at a temperature of 1550°C, and is heated from outside the electric furnace at a speed of 0.1 mm/min to 1.0 mm/min. inserted. Then, after holding for 3 hours,
Cooling was performed by turning off the electric furnace input and using furnace cooling. The density of the obtained crystal was measured by the Archimedes method and was 3.6.
g/cm3, which was 84% of the ideal density determined from the lattice constant. This is insufficient for single crystal growth by the zone melting method.

[0013] The obtained sintered rod was melted in an infrared condensing zone melting furnace and once zone-passed at a speed of 30 mm/h to 70 mm/h to produce a uniform and dense raw material rod. . At that time, the power required for melting was approximately 750 W, and the melting was performed while flowing air into the reactor core tube at a rate of 250 cc/min. When the moving speed of the zone was slower than 30 mm/h, the melt in the zone penetrated into the raw material sintered rod, making it impossible to perform stably. On the other hand, if the speed was faster than 70 mm/h, the raw material would not be able to melt and melt into the zone fast enough, making it difficult to maintain the zone stably.

[0014] The molten raw material thus prepared was again placed in an infrared focusing zone melting furnace, and single crystal growth was performed in an air flow atmosphere of 250 cc/min. Figure 1 shows the layout during installation. In the belt melting furnace shown in FIG. 1, a quartz tube 3 having an inlet 1 and an outlet 2 for atmospheric gas is surrounded by a halogen lamp 4 and surrounded by a spheroidal mirror 5. Crystal growth from the raw material rod M using the seed crystal S is projected onto a screen 7 through a lens 6. Seed crystals do not need to be used, but when growing a single crystal starting from a polycrystal, for example, when growing at 3 mm/h, a seed crystal with a diameter of 2 mm is required.
After necking to about 10 mm and growing to about 10 mm, the crystal was turned into a single crystal. When starting from a seed crystal, single crystals were grown immediately without necking.

[0015] The growth speed is 1 mm/h and 2 mm/h, 4
mm/h, good transparent single crystallization could be obtained in all cases. In all cases, the power required for melting and zone maintenance was approximately 700W.

[0016] Also, La0.5Nd0.5MgAl11O
19 and La0.8Pr0.2MgAl11O19,C
A good single crystal of e0.8Nd0.2MgAl11O19 etc. could also be grown using the same method.

[0017] Also, as an example of the raw material to be fired, L
aMgAl11O19 was selected for explanation, but whether the rare earth element is Ce, Pr, Nd, Sm, Eu, or Gd, or a solid solution thereof, the chemical and physical properties related to sintering will be explained. It is possible to produce a dense sintered rod using exactly the same method without any change in (melting point, reactivity, sinterability, particle size), etc.

[0018]

Effects of the Invention As explained in detail above, by using the single crystal manufacturing method according to the present invention, it is possible to easily obtain a raw material rod that is dense and has little variation in composition, and by using an infrared condensing zone melting furnace. Thus, a single crystal of LnMgAl11O19 can be easily and stably produced. LnMgAl11O19 single crystal is a promising material as a high-power laser oscillation material due to its chemical stability, photothermal conductivity, etc., and has a great influence on industry.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the layout of an infrared condensing zone melting furnace.

[Explanation of symbols]

3 Quartz tube 4. Halogen lamp M Raw material rod S Seed crystal

Claims (1)

[Claims] Claim 1: A method for producing a single crystal of LnMgAl11O19 using an infrared condensing zone melting furnace and growing a single crystal of LnMgAl11O19 by a zone melting method (however, Ln is one of La, Ce, Pr, N
d, Sm, Eu, Gd and their solid solutions), a sintered rod serving as a raw material is melted in an infrared condensing zone melting furnace, and the melting rate is 30 mm/h to 70 mm/h.
A uniform and dense raw material rod is created by zone-passing at a speed of A method for producing a single crystal, characterized by forming a single crystal.