JPH01261258A - Production of ceramic scintillator - Google Patents

Abstract

PURPOSE:To obtain a ceramic scintillator having high light-emission intensity, extremely low scattering of the intensity and excellent uniformity, by adopting a pressing mechanism with a hydrostatic press in the vacuum sealing step in the sintering of a rare-earth metal oxysulfide by HIP process. CONSTITUTION:A rare-earth metal oxysulfide 1 is vacuum-sealed in a metal capsule 2 and sintered under pressure. In the above process, the vacuum-sealing of the metal capsule is performed with a pressing mechanism without applying vibration to the metal capsule. A sealed part 9 can be formed at the tip end of a pipe 3 by using a hydraulic press 6 as a pressing means 7 and pressing the vacuum-sealing part 5 of the pipe 3 protruded from the metal capsule 2 with a cylindrical cemented carbide tip 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic scintillator suitable as a scintillator material for X1iCT that detects radiation.

[Conventional technology]

Conventionally, scintillators used in XIICT etc.
Xenon (Xs) 11! However, the Xe ionization chamber has the problem that it is difficult to miniaturize the device. In recent years, single-crystal scintillator materials, scintillator material powder dispersed and solidified in resin, or rare earth oxysulfide powders have been sintered using the hot isostatic pressing method (HI P@) as highly accurate and compact solid-state detectors. A ceramic scintillator has been proposed (Japanese Patent Application Laid-Open No. 61-12
7670).

However, this ceramic has a problem in that output tends to vary within and between sintered lots. If there are variations in characteristics, they can be treated as multiple elements,
When used as a detector system, it becomes difficult to accurately reproduce information. In particular, uniformity is important for medical applications that require a high degree of accuracy.
It is essential for line CT systems, and its improvement is desired.

Conventionally, when rare earth oxysulfides are sintered using the HIP method, the raw material powder is filled into a metal capsule and sealed in vacuum.
A method is being adopted to do so. When a metal capsule filled with an IM material is vacuum-paired, if vibrations are applied from the outside, unevenness and variation in packing density tends to occur, which is a cause of variation in output in the final sintered body. JP-A-61-127670 does not particularly mention this vacuum sealing method.

[Problem to be solved by the invention]

In view of the above-mentioned circumstances, an object of the present invention is to provide a method for manufacturing a ceramic scintillator that has high luminous output, extremely small variation in output, and excellent uniformity.

[Means to solve the problem]

The above object is achieved by sintering the rare earth oxysulfide by the HIP method and performing this operation with a pressure mechanism using a hydraulic press when the rare earth oxysulfide is sealed in vacuum. During this work, the sealed portion of the exhaust metal pipe is heated to a temperature at which the metal pipe is crushed by pressurization and its inner surface can be brought into close contact with the metal pipe. The pressure required for sealing also depends on the diameter, wall thickness, material, etc. of the metal pipe, but for example, the pressure required for sealing depends on the diameter, wall thickness, material, etc.
When using a 1 m pipe, 3 to 5 tons (conditions under which the pipe material deforms by about 10 to 20%) is used.

[Effect]

A metal capsule is filled with rare earth oxysulfide, and then vacuum sealed and HIP is performed. During this vacuum sealing, by crushing the pipe portion protruding from the metal capsule using a pressure mechanism, it is possible to perform this work without applying vibration to the metal pipe.

When vacuum sealing is performed by vibrating the metal capsule, the rare earth oxysulfide, which is uniformly dispersed within the capsule, tends to become unevenly distributed. When this is subjected to HIP, the sintered body has the disadvantage that density unevenness and microcracks are likely to occur.

If vacuum sealing is performed using the above method, the rare earth oxysulfide inside the capsule can be sintered while being uniformly distributed, eliminating such defects, resulting in very small output variations and high reproducibility. It becomes possible to sinter good ceramics.

〔Example〕

The present invention will be explained in detail below using examples.

FIG. 1 shows an embodiment according to the present invention. A rare earth oxysulfide 1 is uniformly dispersed in a metal capsule 2, and a pipe 3 protrudes from the metal capsule 2, which is partially sealed. The sealing method is to vacuum the other end of the pipe 3 with a vacuum pump 4 to a pressure of about 10 Torr to 10-5 Torr, and then open the vacuum sealing part of the pipe 3 to a pressure of about 8 Torr.
It is heated to 00° C., and an external force is applied by a pressure mechanism 7 using a hydraulic press 6 to crush this portion. The pressurizing mechanism 7 has a cylindrical carbide tip 8 arranged in its sealing section, which is pressed against each other by a hydraulic press 6 to pressurize the vacuum sealing section 5 of the pipe 3. An appropriate value for this pressing force is about 3 to 5 tons when a pipe with a diameter of 12 mm is used. After this work is completed, the metal capsule is transferred to the second
As shown in the figure, the structure is such that a sealing part 9 is located at the tip of the pipe 3.

FIG. 3 shows another embodiment according to the invention. Similar to the embodiment shown in FIG. 1, the metal capsule 2 containing the rare earth oxysulfide 1 is vacuum-sealed with the pipe portion 3. When performing this vacuum sealing, as shown in Fig. 4, the joint part of the pipe 3 of the sealing part 10 is lengthened to prevent damage from this part when external pressure is applied to the metal capsule 2 during HIP. It becomes. For this purpose, as shown in Fig. 3, a planar carbide up 11
It has a structure in which it is pressurized by a hydraulic cylinder 6.

After the vacuum sealing section 12 is bonded using this device, sealing is performed again using the device shown in FIG. 1 to obtain a metal capsule having the shape shown in FIG. 4.

FIG. 5 shows a vacuum sealing device according to the present invention.

A metal capsule 2 is placed on a moving table 13, and this pipe section is heated by a heating burner. Next, the moving table 13
The pipe 3 is moved to the pressure mechanism 15 position, where the pipe 3 is crushed by the planar carbide tip 11. Next, the moving table moves, heats the sealing section again, and seals the sealing mechanism 1.
Move to position 6 and complete sealing with the cylindrical carbide tip. Through this process, the metal capsule shown in FIG. 4 can be obtained.

In addition, before carrying out the above-mentioned sealing cutting operation, it is recommended that the capsule material be subjected to hydrogen annealing or a wire brushing treatment to the inner surface of the sealing cut part to improve the reliability of sealing cutting (vacuum leakage prevention). In addition, to further improve reliability, the seal cutting operation is performed by lightly turning the seal in 2 to 3 locations, and then the normal cutting/separation operation is performed at the final location. This is also extremely effective.

In the above example, the heating temperature was 800°C, but it is possible to cut the seal even at a temperature lower than this, and the heating temperature is 550 to 60°C.
Sufficient vacuum sealing is possible at temperatures above 0°C.

(Vacuum sealing is possible even at room temperature if the deformation rate is about 80%, but it is not practical. If it is about 550 to 600°C, the pressurizing force will increase by 20 to 30%, but the deformation rate will be 800°C.
10 to 20% is sufficient. ) Figures 6 and 7 show the densities of wafers cut out as scintillator material from a block of rare earth oxysulfide sintered under pressure, and their densities successively measured. 6th
The figure shows measurement data from a previous method in which vacuum sealing was performed by applying vibration.

Further, FIG. 7 shows the results obtained by the method according to the present invention. It can be seen that the results according to the present invention have data dispersion about three times better than the previous method.

This makes it possible to inexpensively manufacture a high-performance scintillator with less unevenness in one image, and the effects of the present invention are extremely significant.

Therefore, the ceramic scintillator produced according to the present invention is suitable as a radiation detection element material for X-ray CT and the like, and is of great interest in the medical field and has great industrial effects.

〔Effect of the invention〕

As mentioned above, when rare earth oxysulfide is sintered under pressure, the vacuum sealing method, which uses a pressurizing mechanism and fixes the metal capsule, has a high output and extremely variable output. It is possible to realize a rare earth oxysulfide ceramic scintillator that is small and has excellent uniformity. especially.

Since vacuum sealing can be performed without applying vibrations in the filled state, uneven distribution of components can be sufficiently prevented and crystals that are more homogeneous than ever before can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 3 are cross-sectional views showing examples of vacuum sealing devices used to carry out the present invention, and FIGS.
The figure is a sectional view showing an example of a metal capsule obtained by the present invention, FIG. 5 is a perspective view of an example of a vacuum sealing device used to carry out the present invention, and FIG. A graph showing an example of variation in density between wafers when the conventional method of sealing is performed, and FIG. 7 is a graph showing an example of variation in density between wafers when vacuum sealing is performed using the present invention. It is. 1... Rare earth oxysulfide, 2... Metal capsule,
3... Pipe, 6... Hydraulic press, '7... Pressure mechanism, 8... Cylindrical carbide tip, 11... Planar carbide tip. [etc.] Figure ear prisoner, 5th ward / nei sho de"n i maru Q, cf--tic.

Claims (2)

[Claims] 1. A rare earth oxysulfide is vacuum-sealed in a metal capsule and sintered while pressurized, and the metal capsule is vacuum-sealed using a pressurizing mechanism without applying vibration to the metal capsule. Manufacturing method of ceramic scintillator. 2. A method for manufacturing a ceramic scintillator according to claim 1, characterized in that a static pressure press is used as the pressurizing mechanism.