JPS5933560B2 - Bi↓4Ge↓3O↓1↓2 single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a B14Ge30,2 single crystal for radiation detection.

Nester (Ne5) has shown that 13i4Ge30+2 single crystal has excellent properties as a material for detecting
ter) et al.

Bi4Ge3O12 (hereinafter abbreviated as BGO) single crystal is manufactured by a pulling method.

For pulling, raw materials are filled into a platinum crucible and melted using a high-frequency heating method, and a seed crystal is immersed in the melt and gently pulled up while rotating to form a single crystal.

The obtained single crystal contains few impurities and becomes a good scintillator when there are few air bubbles (voids).

However, BGO has a high viscosity (and voids are likely to occur) in the form of a melt.

Voids are likely to occur (1) when there are many impurities, (2) when a sudden temperature change occurs, and so on.

In addition, (3) it is likely to occur at the end of the hike.

Among these conditions, conditions (1) and (2) can be prevented by ordinary crystal pulling techniques, but it is difficult to prevent conditions (3).

The present inventors believe that the occurrence of voids related to (3) is caused by BGO
They discovered that this phenomenon is unique to the material because it has an extremely high viscosity in the melt state, and invented a method for producing void-free, high-quality crystals at a high yield through a single pulling process.

When producing a single crystal by the pulling method, the crucible used is usually of the same shape as the diameter (height and depth).

This is to make the internal volume as large as possible for the size of the crucible, and a crucible with a low height will be inefficient.
This is because a crucible that is two or three times as high as the crucible makes it difficult to pull crystals.

When producing a single crystal by the pulling method, if a crucible with a height equal to the diameter of the crucible is used, usually about 80% of the raw material in the crucible can be made into a single crystal, all of which will be high quality crystals.

However, in the case of BGO, since it has a high density and especially a high viscosity, voids occur in the lower part of the crystal, and the amount of good quality crystals is about 60% of the filled raw material.

The method for manufacturing a BGO single crystal is as shown in Fig. 1. First, a platinum crucible 1 is filled with BGO raw material 2, heated to form a melt, and the melt is filled to a surface level 3, and a seed crystal 4 is placed in a platinum crucible 1 as shown in Fig. 2. As shown in FIG. 2, when the crystal is pulled up, a long single crystal 5 grows, and the melt level 6 falls (the limit position at which a high-quality crystal can be formed).

That is, when the melt level reaches 6, voids I are generated in the crystal.

The void 7 is characterized in that it occurs when the depth of the liquid surface becomes smaller than the diameter of the crystal.

Carefully observing the melt surface during pulling, we found that when the melt level was 6 or higher, the forced convection of the melt due to the rotation of the crystals reached the crucible wall, but when the melt level was below 6. In this case, forced convection is limited to the periphery of the crystal and does not reach the crucible wall.

The present inventors conducted the above experiment using a low-height crucible and found that voids occur when the melt level in the crucible becomes less than the crystal diameter.

In other words, it has been found that when a crucible with a low height is used, the yield of good quality crystals without voids is poor, whereas when a crucible with a high height is used, the yield is improved.

FIG. 3 shows the state at the final stage of single crystal pulling, and 8 represents residual melt, which corresponds to about 20% of the raw material.

An object of the present invention is to provide a method for producing a BGO single crystal with a high yield and good quality, that is, a BGO single crystal with few voids.

The present invention relates to a method for producing a BGO single crystal, which is characterized in that the BGO single crystal is pulled using a crucible whose height is at least higher than the diameter of the crucible.

The present invention will be explained in detail below.

Inner diameter is 70 mm and height is 50,70.105.140.1
．． A 75 mm platinum crucible is used, and for each of these height crucibles, the diameter of the single crystal is 30.35.4
Crystal growth was performed on three types of 0 birds.

The pulling is done by high frequency heating method and the pulling speed is 3m.
It was set as m1 hour.

Table 1 shows the yield of good quality crystals under various conditions.

As is clear from Table 1, when the height of the crucible was high and when the crystal diameter was small, high-quality crystals could be produced with a high yield.

According to the present invention, since the BGO raw material is filled in a crucible whose height is higher than the diameter of the crucible and the single crystal is pulled, high quality crystals can be produced with a high yield, and the industrial effect is high.

[Brief explanation of drawings]

FIG. 1 to FIG. 3 are BGO for explaining the present invention.
These diagrams show the progress of crystallization of a single crystal. Figure 1 is a cross-sectional view at the early stage of single crystal pulling, Figure 2 is a cross-sectional view at the middle stage of single crystal pulling, and Figure 3 is a cross-sectional view at the final stage of single crystal pulling. . Explanation of symbols, 1...Platinum crucible, 2...
・BGO raw material, 3... Melt surface level, 4... Curved seed crystal, 5... Single crystal, 6... Melt level, 7...・Void, 8...Residual melt.

Claims (1)

[Claims] 1. A method for producing a B 14 Ge 3012 single crystal, which comprises pulling the B 14 Ge 30.2 single crystal using a crucible whose height is at least higher than the diameter of the crucible.