JPS6133613B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a getter device and a getter composition suitable for use in discharge tubes or containers, vacuum tubes or containers, rare gas-filled tubes or containers, etc. that use non-evaporable getter metals. Hitherto, such getter devices have been made in the form of open metal cups or pots and have been associated with insulated heating coils of the cathode type that are indirectly heated. Such metal containers have been made of solid metal or at least have a surface coating of such metal. Getter devices using zirconium, particularly relatively thick layers of zirconium produced by pressing and sintering zirconium powder, provide significantly increased gas sorption rates and gas sorption capacities at temperatures above 600°C, but intermediate and at low temperatures, the gas sorption capacity is quite limited. This is due to the fact that the gas diffusion into the interior of the zirconium is reduced so that the gettering effect only occurs mainly due to a small surface sorption of the zirconium. However, obtaining an increase in the gas sorption capacity of the getter at room temperature is absolutely necessary to ensure the maintenance of the desired vacuum or noble gas atmosphere in electron tubes and other equipment under storage conditions. Increased gas sorption capacity at room temperature can be achieved using porous, uncompressed zirconium bodies.
In an attempt to achieve increased porosity in partially sintered bodies of zirconium powder for gettering purposes, molybdenum or tungsten powder has been mixed with zirconium powder. However, this strategy does not work, especially when zirconium and molybdenum are heated to 1500°C.
(2732〓) and as a result have the disadvantage that the sintering and degassing temperatures of such working electrodes are severely constrained in their upper limits. U.S. Pat. No. 2,855,368 discloses the addition of various pulverulent materials that chemically or physically react with pulverulent zirconium to reduce the temperature at which activation of the zirconium occurs, thereby reducing the likelihood that complete sintering will occur. It suggests. Among others, mention may be made of aluminum, silicon, beryllium, tungsten, cerium and lanthanum. However, such reactions cannot be well controlled and therefore do not yield products with consistent properties. In fact, this document suggests the addition of high melting point metal powders such as tungsten to reduce sintering of the zirconium.
_TiAl3 has also been suggested as an anti-sintering agent. The use of non-metallic anti-sintering agents has also been proposed, for example US Pat. No. 2,368,060 describes the addition of powdered silica. In another attempt to overcome the sintering problem of Zr powder non-evaporable getters, U.S. Pat.
No. 3,584,253 proposes the use of graphite powder as an anti-sintering agent to maintain a large surface area of the active gas sorption material. These so-called "sintering inhibitors"
It should be understood that this does not prevent sintering, but only suppresses sintering to the extent that it can be more easily controlled. Although graphite greatly reduces the introduction of toxic gases into electron tubes and other equipment compared to previous proposals for metal additions such as molybdenum or tungsten powder, graphite still introduces unwanted gases into electron tubes. It must be recognized that the introduction of Other anti-sintering agents such as refractory metal oxides such as silica or other species oxides are also known to introduce significant amounts of toxic gases into the electron tube. US Pat. No. 3,926,832 describes the use of zirconium-aluminum alloys as anti-sintering agents. This alloy itself is a getter material. In order for this getter composition to have gas sorption properties, these
It is activated by heating to high temperatures such as 900°C. Unfortunately, the use of such high activation temperatures results in a number of drawbacks, including: 1. Precise control of the activation temperature in industrial processes for activation of getter compositions is difficult. If the temperature is increased even slightly above the recommended value, excessive sintering will occur, leading to a reduction in getter properties. 2 The above results show that the getter properties of getter devices can vary from device to device. 3. A large amount of energy is consumed in activating the getter device. 4. The high temperatures involved in many applications where it is desired to use getter devices can easily damage nearby components. To prevent such damage, complex and expensive measures have to be taken, and their effectiveness is limited. 5. High temperatures cause undesired and toxic gases to be released from the walls of the container in which the getter device is placed and from nearby components. 6. To achieve high activation temperatures using current heating methods, a metal wire or feeder penetration carries the current from outside the container in which the getter device is housed. These feeder sections use glass-to-metal seals and are susceptible to vacuum leaks when large temperature differences are encountered. Furthermore, large diameter wires must be used to carry high currents, which poses even greater difficulty in fabricating the hermetic feeder section. 7. If the vacuum container becomes damaged due to air entering during the activation process of the getter device at high temperatures, an exothermic or explosive reaction is likely to ensue, which is extremely dangerous. It is therefore an object of the present invention to provide an improved getter device and getter composition that substantially obviates the disadvantages of the prior art. Another object of the present invention is to provide a getter composition that has superior gettering properties over conventional getter compositions even after activation at lower temperatures than required for conventional getter compositions. That's true. Yet another object is to provide a getter device that can be activated without the risk of excessive sintering. It is also an object of the present invention to provide a getter device that allows the amount of energy for activation to be reduced. Another object is to provide a getter composition and device that is easy to apply and safe to use. According to the invention, zirconium-vanadium-
A non-evaporable getter composition is provided that includes at least a first getter metal selected from titanium and zirconium in intimate admixture with an iron alloy. These alloys themselves are non-evaporable getter materials and have (1) sorption capacity for noxious or toxic gases such as oxygen, carbon monoxide, water vapor, etc. and (2) excellent properties at 1000°C.
Characterized by a vapor pressure of less than 10 ^-5 Torr (1.3 x 10 ^-3 Pa). The present invention starts from the concept of using Zr-V-Fe alloy in combination with the first non-evaporable getter metal, and complete sintering of getter metal grains is achieved by using Zr-V-Fe alloy grains. Avoided during heat treatment by using These are, for example, Zr-V-
It is used by mixing the Fe alloy powder and the first getter metal powder and coating the mixture with a known manner of post-supporting means. By adding Zr--V--Fe alloy grains, a pressed layer with a higher porosity can be achieved than, for example, when using ductile molybdenum or tungsten. The getter device of the present invention can be particularly suitably used in applications where space is limited. According to one method of the present invention for producing a getter device of the type described above, the heating means provided with an insulating layer in advance contains powdered Zr and powdered Zr-V-
It is coated accordingly with a mixture of Fe alloys and subsequently heat treated at 800-900°C in high vacuum.
The powder mixture may be applied in the form of an alcoholic suspension by a dipping operation, or the dry powder mixture may be placed in a mold and subjected to the desired heat treatment. Alternatively, the mixed getter powder can be supported as a layer of particles on at least one side of a carrier metal strip by methods such as those described in US Pat. Nos. 3,652,317 and 3,856,709. The powder may also be pressed directly into a ring-shaped holder, as is well known in the art, or applied in the form of a liquid suspension directly onto a suitable surface, such as an electron tube electrode. Getter devices and compositions produced in accordance with the teachings of the present invention generally exhibit higher gas sorption rates at ambient temperatures after activation at temperatures of 500° C. or less than conventional getter devices and compositions. Shows sorption rate and capacity. Titanium or zirconium is made of US standard sieves.
It is provided as a fine powder passing through 200 meshes/inch (79 meshes/cm), preferably 400 meshes/inch (158 meshes/cm). Zr-V-Fe alloy is based on weight percent Zr-V
- Fe has a composition that falls within the triangle defined by the following points when plotted on a ternary composition diagram (13th
(See figure): a 75%Zr-20%V-5%Fe b 45%Zr-20%V-35%Fe c 45%Zr-50%V-5%Fe The preferred composition is as follows: Inside the polygon: d 70%Zr-25%V-5%Fe e 70%Zr-24%V-6%Fe f 66%Zr-24%V-10%Fe g 47%Zr-43 %V-10%Fe h 47%Zr-45%V-8%Fe i 50%Zr-45%V-5%Fe Zr-V-Fe getter alloy itself is patented in U.S. Patent Application No. 115051 dated January 24, 1980. It is stated in the number. The particle size of the ternary alloy is 60 meshes/inch (24 meshes/cm), preferably 120 meshes/inch (47 meshes/cm) based on the U.S. Standard Sieve Criteria.
It is said to be something that passes through a sieve. The ternary alloy grains are generally larger than the zirconium grains and are uniformly distributed throughout the zirconium grains. The ternary alloy grains are spaced apart without generally touching each other, while the zirconium grains are generally in contact with each other. The weight ratio of zirconium to ternary alloy is from 4:1 to 1:6, preferably from 2:1 to 1:2. This intimate mixture can be supported by a holder if desired and is then partially sintered by heating in vacuum at a temperature of 800-900 DEG C. for about 10 minutes.
Partial sintering causes the first getter metal grains to adhere to each other without substantial reduction in their surface area so that the getter device maintains a high porosity. After cooling to room temperature and removal from the vacuum chamber, the composition has at least
50, preferably at least 100 Kg/cm ² . After exposure to air, the getter structure of the present invention is placed in an evacuated vessel where it sorbs active gas after activation. Activation is accomplished by heating the getter structure to a temperature sufficient to render it gas sorbing, generally from 200 to 700°C, preferably from 300 to 600°C, for 1 to 30 minutes. The lower the temperature and the shorter the time,
Sorption rate and capacity will be insufficient. If the temperature is too high and the time is too long, there is a risk that complete sintering will occur, resulting in a reduction in sorption rate and capacity. The getter structures of the present invention are particularly useful because they can be activated at temperatures as low as 450°C. The holder can take any physical form that supports the getter composition. In one embodiment, the holder is an annular ring similar to those commonly used to hold vaporizable getter metals such as barium. In another embodiment, the holder may take the form of a substrate, preferably metallic, and having the particulate composition embedded on at least one of its surfaces. In yet another embodiment, the holder is in the form of a wire or rod around which a pill or pellet of getter composition is formed. The present invention can be applied to a wide variety of exhaust containers.
An evacuated container is a container from which some or most of the ambient air is removed. Some vent vessels generally exhibit pressures below 10 ^-3 Torr and preferably below 10 ^-6 Torr. Some vent vessels have some or all of the air replaced with noble gases. Noble gases are chemically inert, such as xenon, krypton, neon or helium. Examples of exhaust vessels include inorganic receiving and transmitting tubes, x-ray tubes, television and radar kinescopes, klystrons, traveling wave tubes, and mercury discharge tubes, including fluorescent lamps, among others. Furthermore,
The present invention can also be applied to rare gas purification equipment, hydrogen purification equipment, vacuum showers, video intensifiers, and vacuum pumps. Referring now to FIGS. 1 and 2, an apparatus 10 of the present invention is shown. In the getter device 10, the holder is in the form of an annular ring 11 with a groove 12 and a non-evaporable getter composition 13 contained therein. Referring to FIGS. 3 and 4, getter device 30,
30' and 30'' are shown connected. The getter devices 30, 30', 30''... constitute a continuous series of devices. In the device 30, the holder is in the form of a substrate 31 partially embedded in its upper and lower planes with a getter composition 32 in particulate form.
In operation, for example, the getter device 30' removes the devices 30 and 30'' by cutting the substrate 31 in the vicinity of the small bridging attachments 33, 34, 35 and 36.
can be separated from FIG. 5 shows a getter device 50 having a cylindrical form. Here, the holder is in the form of a helical heating wire 51 coated with an electrically insulating coating 52 . Getter composition 53 is molded around. FIG. 6 shows a non-evaporable getter device 60 in the form of a pellet. Here, the holder 61 is a high ohm resistance insulated wire in the form of a heating coil 62 around which a getter composition 63 is formed. FIG. 7 shows a non-evaporable getter device 70 in which the holder consists of a helical wire 71 covered with an electrically insulating coating 72 and heatable by the application of electricity. The adherend of the getter substance 73 is coated by a well-known method. Referring now to FIG. 10, a getter composition 80 of the present invention is shown. Composition 80 includes sintered granular zirconium grains 81, 81'. The composition also includes grains 82, 82' of Zr-V-Fe alloy. The grains 82, 82' of the Zr--V--Fe alloy are larger than the grains 81, 81' of the getter metal. It can be seen that the Zr-V-Fe alloy grains 82, 82' are distributed throughout the getter metal grains 81, 81'. Furthermore, Zr−
The grains 82, 82' of the V-Fe alloy are separated and dispersed without contacting each other. Referring to FIG. 11, grains 81 and 8 in FIG.
An enlarged view of a portion of 1' is shown. grain 81,8
The grains 83, 83' corresponding to 1' are in contact with each other and sintered together. Sintering is carried out for a period sufficient to give the composition a compressive strength of at least 50, preferably at least 100 Kg/cm ² . FIG. 12 shows an image intensifier 120. This has dimensions of approximately 4 cm long x 3 cm diameter. It comprises a curved glass element 130, one surface of which is coated with a photosensitive layer 140 for receiving a low intensity light image. The photosensitive layer 140 is primarily composed of alkali metal deposited in-situ from a small alkali metal dispensing device (not shown). A set of acceleration and convergence electrodes 150, 16
0 are spaced apart and held in constant relationship by a glass cylinder 170. Flat glass plate 180
Phosphor layer 190 for forming an enhanced image
is carried. The getter device 50 consists of a getter structure of the present invention supported directly on a molybdenum wire placed within the image intensifier and attached at both ends to the power transmission sections 210,220. The image intensifier is tube 230
and the pressure is 10 ^-3 Torr (1.3
×10 ^-1 Pa) or less, the getter device 50
Heat to 500° C. for less than 30 minutes, then tube 230 is sealed. This ensures that the alkali metal does not evaporate from the photosensitive layer 140 due to excessive heat and further ensures that any de-glassing of the nearby electrode or glass is reduced to a minimum. The present invention will be further explained based on specific examples. Percentages and parts are by weight unless otherwise specified. Example 1 (Reference Example) This example illustrates a method for preparing a ternary alloy of Zr, V and Fe. 2844 g of Zr with a purity of more than 98% obtained from Kozin Kuhlmann was mixed with 1160 g of Fe-V alloy ingots with a nominal composition of 18% Fe-82% V and approximately 99% pure obtained from Miurex. It was done.
The mixture was placed under vacuum in an induction melting furnace. After switching on the induced current, the mixture melted immediately. The induced current caused the melt to mix completely, and then the melt was rapidly cooled to room temperature. After taking out from the furnace, the produced ternary alloy Zr-V-
The Fe ingots were crushed and ground to a powder having a particle size that passed through a 120 mesh/inch (47 mesh/cm) US standard sieve. Powder is 70% Zr - 24.6% V - 5.4% Fe (excluding impurities)
It had the following composition. EXAMPLE 2 (COMPARATIVE EXAMPLE) Tests in this example were conducted to demonstrate the performance of prior art getter devices. Granular zirconium receives U.S. patent no.
Granular 84% Zr-16% as taught in No. 3926832
Mixed with Al alloy. Getter device 50, illustrated as 50 in FIG.
To fabricate a conventional getter device with a similar structure, the particle mixture was loaded into a 4 mm diameter x 7 mm deep graphite mold in which an electrically insulated helical heater was pre-centered. Ta. This getter device, while still in the graphite mold, was heated to approximately 10 ^-5 to 10 ^-6 torr (1.3 x 10 ^-3 to 1.3 x
It was placed in a vacuum furnace with a vacuum degree of 10 ^-4 Pa).
The temperature was increased from room temperature to 875°C in 35 minutes.
The temperature of 875°C was maintained for another 10 minutes. The thus treated getter device was allowed to cool to room temperature and removed from the post-vacuum oven. A getter device is attached to the thermocouple in a manner well known in the art for the measurement of its getter action characteristics and ^is
It was installed in a vacuum system capable of achieving pressures below Torr. The entire system was degassed by heating at 350°C overnight. The pressure in the system is 10 ^-7 torr (1.3×
on the order of 10 ^-5 Pa), the Getter device was activated by energizing the helical heating wire so that its temperature reached 500°C in 10 minutes. system again
When the Getter device is at a pressure on the order of 10 ^-7 Torr and the Getter device is cooled to room temperature, carbon monoxide is generated so that the CO gas pressure (Pa) above the Getter device is 3 × 10 ^-5 Torr (4
11 c.c./sec (relative to CO) was allowed to flow into the system through the inlet to maintain a constant value of 10 ^-3 Pa). At various intervals (t), P
The CO gas pressure (Pm) at the inlet required to maintain a constant value was measured. From the values of Pm, Pg, t, and C obtained, it is found that CO as a function of the total amount of gas sorbed by the Getter device.
Gas sorption rate curves were drawn. This result is the 8th
It is shown as curve 1 in the figure. In Figure 8, the vertical axis of the display Y shows the sorption rate S (cm ³ /sec), and the horizontal axis of the display X shows the amount of sorbed gas (cm ³ Torr).
shows. Example 3 (Comparative) The same process as Example 2 was repeated, except that the activation step was carried out at a temperature of 450°C. The results are shown as curve 2 in FIG. Example 4 (Comparative) The same process as Example 2 was repeated in all respects except that the test gas used was _H2 instead of CO. The results are shown in FIG. 9 as curve 1'. The vertical and horizontal axes in FIG. 9 are the same as in FIG. 8. Example 5 (Comparative) A process similar to Example 3 was repeated in all respects except that the test gas used was _H2 instead of CO. The results are shown in FIG. 9 as curve 2'. EXAMPLE 6 Tests in this example were conducted to demonstrate the performance of the getter device of the present invention. Example 2 except that the 84% Zr-16% Al alloy is replaced with an equal volume of Zr-V-Fe alloy produced according to Example 1 and the sintering temperature is 850°C instead of 875°C. The process was repeated. Thus, the getter composition of this example is a ternary alloy of 56.2% Zr and 43.8% Zr-
Consists of V-Fe. The results are shown as curve 3 in FIG. Example 7 The process of Example 6 was repeated except that activation was carried out at a temperature of 450°C. The results are shown as curve 4 in Figure 8. Example 8 The process of Example 6 was repeated except that the test gas used was _H2 instead of CO. The results are shown in FIG. 9 as curve 3'. Example 9 The same procedure as in Example 7 was repeated except that the test gas used was H ₂ instead of CO. The results are shown in FIG. 9 as curve 4'. Example 10 (Example) The titanium powder having a particle size of 44μ or less is the Zr of Example 1.
- V - mixed with Fe powder, 47% Ti - balance Zr -
A mixture of V-Fe was prepared. A portion of the powder mixture was placed in a mold surrounding an insulated spiral heating source. It was then heated to 850° C. for 10 minutes under a vacuum better than 10 ⁻⁵ Torr. The getter device thus produced was allowed to cool to room temperature and removed from the post-vacuum chamber. Good results were observed as in the case of Zr. From FIG. 8, by comparing curves 3 and 4 with curves 1 and 2, it can be seen that at 25°C, the getter material of the present invention has an already higher yield than that of the prior art after activation at either 500°C or 450°C. It can be seen that for a given amount of gas sorbed there is a higher CO sorption rate. By comparing curves 4 and 1, it can be seen that even when the getter material of the present invention is activated at 450 °C and 500 °C
It can be seen that it has a higher CO sorption rate compared to the prior art getter material after activation at °C. As can be seen in FIG. 9 by comparing curves 3' and 4' with curves 1' and 2', the getter materials of the present invention outperform the prior art getter materials after activation at either 500°C or 450°C. Has a higher _H2 sorption rate. By comparing curves 4' and 1', it can be seen that the getter material of the present invention has a
It has a higher H ₂ sorption rate than that of the prior art after activation at °C. The superiority of the present getter material becomes even clearer with reference to the following table which shows the sorption rate S at various values of sorbed gas Q taken from the curves of FIGS. 8 and 9. The ratio of the sorption rate of the getter material of the invention to the sorption rate of the prior art getter material is also listed in Tables. For example, the last column of the table shows that the getter materials of the present invention are at least twice as fast as the prior art getter materials when pumping H ₂ after activation at 450°C. Tables 1A, A, A, and A are simply converted values of tables, and.

【table】

【table】

[Table] * Extrapolated value

【table】

【table】

【table】

[Table] * Extrapolated value

【table】 [Brief explanation of the drawing]

FIG. 1 is a top view of an example of the getter device of the present invention, FIG. 2 is a sectional view taken along line 2-2 in FIG. 1, and FIG. 3 is a top view of another example of the getter device. 4 is a sectional view taken along line 4-4 in FIG. 3, FIGS. 5 and 6 are partial sectional views showing still another example of the getter device, and FIG. 8 and 9 are partial cross-sectional views of another getter device;
The figures are graphs comparing the performance of the getter compositions of the present invention and the prior art, FIG. 10 is a schematic diagram depicting the structure of the getter composition of the present invention at a magnification of about 110 times, and FIG. is the circled part in Figure 10 (approximately 40
FIG. 12 is a longitudinal cross-sectional view of an image intensifying device utilizing the present invention, and FIG. 13 is a schematic view of a ternary alloy useful in the present invention. It is a composition diagram. 10, 30, 50, 70: Getter device, 13,
32, 53, 63, 73: Non-evaporable getter composition, 11, 31: Annular ring, substrate, 51, 6
1,71: heating wire, 80: getta composition, 80,
81': Zirconium or titanium grains, 82,8
2': Zr-V-Fe grains.

Claims (1)

Claims: 1. (A) A first partially sintered granule selected from the group consisting of titanium and zirconium and having a particle size that passes through a 200 mesh/inch (approximately 79 mesh/cm) U.S. standard sieve. and (B) a ternary alloy of zirconium, vanadium and iron, whose composition in weight percent is (a) 75%Zr-20%V-5%Fe (b) 45 %Zr-20%V-35%Fe (c) 45%Zr-50%V-5%Fe
a second particulate getter material that passes through a US standard sieve (cm) and is larger than the zirconium or titanium particles. 2. The getter structure according to claim 1, wherein the titanium or zirconium particles have a size that allows them to pass through a 400 mesh/inch (approximately 158 mesh/cm) American standard sieve. 3. The getter structure of claim 1, wherein the ternary alloy grains have a size that allows them to pass through a 120 mesh/inch (approximately 47 mesh/cm) American standard sieve. 4 The following points when the ternary metals are expressed in weight percent on the ternary composition diagram: (d) 70% Zr - 25% V - 5% Fe (e) 70% Zr - 24% V - 6% Fe (f) 66%Zr-24%V-10%Fe (g) 47%Zr-43%V-10%Fe (h) 47%Zr-45%V-8%Fe (i) 50%Zr-45%V- A getter structure according to claim 1, wherein the getter structure lies within a polygon defined by 5% Fe. 5. A getter structure according to claim 1, wherein the ternary alloy grains are uniformly distributed throughout the zirconium to titanium grains and are spaced apart such that they do not substantially contact each other. 6. The getter structure according to claim 1, wherein the weight ratio of A:B is in the range of 4:1 to 1:6. 7 (A) Granular zirconium that passes through a 400 mesh/inch U.S. standard sieve, and (B) a granular ternary alloy of zirconium, vanadium, and iron whose composition, expressed in weight percent, is ( d) 70%Zr-25%V-5%Fe (e) 70%Zr-24%V-6%Fe (f) 66%Zr-24%V-10%Fe (g) 47%Zr-43% V−10%Fe (h) 47%Zr−45%V−8%Fe (i) 50%Zr−45%V−5%Fe / inch (47 mesh/
cm), and which are larger than the zirconium grains and uniformly distributed throughout the zirconium grains, in which case the weight ratio of (A) and (B) is 2. :1～
1:2 and the ternary alloy grains are generally spaced apart without contacting each other, and (a) the composition exhibits a compressive strength of at least 100 Kg/cm ² , and (c) the zirconium grains The getter structure according to claim 1, wherein the getter structures are in contact with each other. 8 (A) selected from the group consisting of titanium and zirconium and having a density of 200 mesh/inch (approx.
(B) a ternary alloy of zirconium, vanadium and iron, expressed in weight percent; In the ternary composition diagram, the composition is (a) 75%Zr-20%V-5%Fe (b) 45%Zr-20%V-35%Fe (c) 45%Zr-50%V-5%Fe a second particulate getter material that lies within a triangle connecting the defined points and whose particles pass through a 60 mesh/inch (24 mesh/cm) US standard sieve and are larger than the zirconium or titanium particles; placing a getter structure in the container; evacuating the container; heating the getter structure to a temperature sufficient to activate it; and sealing the container. Method. 9. The method according to claim 8, wherein the heating is carried out at a temperature of 200 to 700°C. 10 (A) granular zirconium that passes through a 400 mesh/inch U.S. standard sieve, and (B) a granular ternary alloy of zirconium, vanadium, and iron whose composition, expressed in weight percent, is (d) in the ternary composition diagram. ) 70%Zr-25%V-5%Fe (e) 70%Zr-24%V-6%Fe (f) 66%Zr-24%V-10%Fe (g) 47%Zr-43%V −10%Fe (h) 47%Zr−45%V−8%Fe (i) 50%Zr−45%V−5%Fe a granular ternary alloy which passes through an inch American standard sieve and is larger than the zirconium grains and uniformly distributed throughout the zirconium grains, where the weight ratio of (A) and (B) is 2: 1~
1:2 and the ternary alloy grains are generally spaced apart without contacting each other, and (a) the composition is partially sintered, and (b) the composition has a particle size of at least 300 Kg/cm ² . ( ^c ) placing a getter structure ⁱⁿ a container in which the zirconium grains are in contact with each other; Evacuate the getter structure to a temperature of 300 to 600℃ for 1 to 30 minutes.
9. The method of claim 8, comprising the steps of: heating for a minute; and sealing the container. 11. The method of claim 8, including the step of at least partially enclosing the container with a rare gas before sealing the container.