JPS6027681A - Production of bapb1-xbixo3 single crystal by solution pulling method - Google Patents

Abstract

PURPOSE:To produce the titled single crystal by the solution pulling method, rapidly, in high efficiency, by mixing and melting lead monoxide, barium carbonate and bismuth dioxide, cooling the molten liquid, and growing the separated minute crystal on a seed crystal. CONSTITUTION:A mixture of about 20mol% BaCO3, about 65mol% PbO and about 15mol% Bi2O3 is put into the platinum crucible 9, heated and melted by induction heating with the high-frequency heating coil 4, and a seed single crystal 7 of formula (x is 0-0.4) is brought into contact with the surface of the molten liquid 8. The molten liquid 8 is cooled slowly, and the minute crystal of formula is deposited slowly at the part having lowest temperature, i.e. at the interface between the molten liquid 8 and the seed crystal 7, and crystallized on the seed crystal 7. The objective single crystal of formula is obtained by pulling up the grown single crystal slowly from the molten liquid 8.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a method for producing BaPb, -xBi by a solution drawing method.
The present invention relates to a method for producing an x0B single crystal.

Conventionally, as a means to obtain a single crystal Yt of a substance that undergoes a peritectic reaction by decomposition melting at high temperatures and cannot be grown as a single crystal by the normal pulling method, 1. Usually, the target substance is mixed in a solvent and the temperature of the mixed melt is lowered. A flux method is used in which the mixed melt Z is brought to a state of a supersaturation concentration or higher, and the target substance is precipitated from the melt as a single crystal.

This invention is based on a BaPb solution pulling method in which a single crystal of a target substance is precipitated as a microcrystal on a seed crystal from the above-mentioned solvent mixture, and is grown while being pulled up.
, -xBi! 01 single crystal manufacturing method.

Ba Pb, □Bix0. The perovskite crystal structure has a conduction transition temperature Tc of about 13, which is the highest transition temperature among superconducting materials that do not devour transition metals.It is known as a compound superconductor. It is expected to be applied in the future as a cryogenic device 1, and for this purpose, a large, high-quality single crystal is desired, and the development of a manufacturing method for the same is desired.

When x = 0 in HaPb1-xBix03, as the temperature is increased, it decomposes and melts into a liquid phase with BJL and pbo4 at around 1080°C, so a single crystal cannot be produced from a raw material with the same composition as a single crystal. Therefore, the Czochralski method cannot be applied, and in the past, pbo, , pb,
o.

Crystal growth is carried out by the flux method using KCI, KCI and BaCl as a flux. However, this flux method has only been reported to have a maximum area of 3 x 3 mm and a thickness of 0.5 ff111 or less.

This invention was made in view of the above points, and contains lead monoxide (PbO) and barium carbonate (Ba
By mixing COs ) and bis-vs (Bit03)Y dioxide and lowering the temperature of the melt, the Ba Pb In this method, Ba pb, , xntxo is produced by a solution pulling method. Unlike the flux method, high-quality single crystals of any size can be produced in a desired direction using seed crystals. This invention will be explained in detail below.

First, the principle of this invention will be described. Figure 1 shows BaC0,-P drawn from differential thermal analysis and actual crystal growth experiments.
It is a phase equilibrium diagram of the bO system. BtCOB is 50 mol%,
When BaPb01 having a composition of 50 mol % of pbo is heated, it decomposes and melts into a liquid phase of Ba and PbO4 at around 1080°C. Therefore, the Czochralski method, which pulls up crystals with the same composition as the melt, cannot be applied. Next, the raw materials mixed in a composition ratio between liquid phase 11JA-3, that is, 34 to 4 mol% of BaC01 and 66 to 96 mol% of pbo, are heated and melted at about 1080 to 850°C, and then the melt is When the temperature is gradually lowered, the composition of the melt shifts to the right in the diagram along the liquidus line A - B K, and B
a Pb O, becomes a solid phase and precipitates. In this phase equilibrium diagram, when a small amount of some other different element is mixed at the positions of Ba atoms and Pb atoms, if the phase equilibrium diagram does not qualitatively change, BaPbO5 solid solution will precipitate in the same phase ( .

Therefore, even if the position of pb atom is changed to YBiBa atom, the first
Since this is essentially the same as the phase equilibrium diagram of the BaC0, -PbO system shown in the figure, crystal growth of Ba pb, -xnsxo is possible.

In the conventional 7-lux method, PbO,, Pb, 04. K
C.I.

BaPb1-xB1 in a solvent such as BaC1! After crystal growth, only the solvent was removed using chemicals, or the crucible was removed from the furnace during slow cooling and only the unsolidified solvent was discarded, and the Bapbl-xBtxo single crystal was taken out. In this way, if you do not use v5 for a long time with chemicals or perform dangerous operations, the solidified product of the melt and BaPb, -xBlBi
x01 single crystal separation was not possible.

In this invention, the same BaPb1-! Bl, 01
BaPb precipitated on the single crystal seed crystal, -! Bl
! 03 This method uses a method of growing and pulling a single crystal.

FIG. 2 is a diagram for explaining one embodiment of this invention.
b,-! Bthxo manufacturing equipment. This manufacturing equipment is equipped with a crystal growth observation window to isolate toxic PbO vapor from the manufacturer.

In this figure, 1 is a water cooling shaft, 2 is a platinum shaft, 3 is a heat insulator, 4 is a high frequency heating coil, 5 is a thermocouple, 6 is a crucible support, T is a BaPb+-xBixom single crystal, 8
is the starting material, and 9 is the platinum crucible.

Next, the manufacturing method will be explained.

Starting material ati - as an example, BaC01'& 20 mol%
, pbo to a composition of 65 mol % and old tOS 15 mol %, placed in a platinum crucible 9 with a diameter of 50 m and a height of 35 mm, which also serves as a heating element, as shown in Fig. M2, and heated by induction heating using a high-frequency heating coil 4. After heating to ~1080°C to melt, the seed crystals Ba pb, -xBtxo,
Single crystal T is brought into contact with the surface of the melt. When the temperature of the melt is gradually lowered, B a P b 1-z B l z appears at the interface of the melt that is in contact with the seed crystal with the lowest temperature in the melt.
OB microcrystals precipitate little by little and crystallize on the seed crystals. The single crystal grown in this way is gradually pulled out of the melt. That is, while cooling the melt, the grown single crystal is pulled up at the same time.

The manufacturing conditions at this time are BaPb1-xBl, O
.

The pulling speed of single crystal T is 0.3~l wa/h
r, melt temperature cooling rate 2 to 10°C/hr, crystal rotation number 10 to 30 rpm, and atmosphere in air. Moreover, the time required to complete the growth of BaPbI and Bix01 single crystals was only 5 to 6 hours to obtain a single crystal of about 10I.

In the production method of this invention, the position of the pb atom in the crystal is changed to B
Even if the a atom is replaced, the phase equilibrium diagram of the BaC03-pbo system in Figure 1 remains essentially the same, so BaPb5-x
Bixos single crystal has been manufactured. Ba Pb5-, B
It is possible to grow a single crystal with a composition in the range of 0x<:0.35, where ix0@ indicates superconductivity. Similarly, when a small amount of some kind of different element is mixed at the positions of Pb atoms and Ba atoms in the crystal, the phase equilibrium diagram qualitatively changes to BaC0B-pb as shown in Figure 1.
o-system peace-peace equilibrium diagram If there is no difference essentially, the B
It is also possible to produce a pb,-, n1xo, solid solution single crystals.

The single crystal produced as described above takes about 5 days compared to the single crystal grown using the conventional flux method.
Compared to the size of X 0.5 turn or less, a crystal with a size of 30 x 30 x 1 m can be obtained in 5 to 6 hours, which has the advantage that a large single crystal can be produced in a short time.

[Brief explanation of the drawing]

wJ1 diagram is BaC0 for detailed explanation of this invention.
3-pbo system phase equilibrium diagram. FIG. 2 is a block diagram of a manufacturing apparatus for Bapb, -xBt, o, and single crystals for explaining one embodiment of the present invention.

Claims (1)

[Claims] By mixing lead monoxide, barium carbonate, and bismuth dioxide and heating and melting them, the general formula B is obtained by cooling the melt.
a pb, -xni! o, in the formula x −
B a characterized by precipitating microcrystals of 0.00 to 0.4 and growing the crystals by crystallizing them on the seed crystals.
A method for producing P b s -x B 1 x OB single crystal using a solution pulling method.