SU1115619A1 - Material for cold cathode and method of manufacturing same - Google Patents

Abstract

1. Material for the cold cathode of electronic devices, including cesium or rubidium aluminosilicate, characterized in that, in order to ensure the stable operation of the cathodes under conditions of intense ion bombardment, it additionally contains nickel and consists of an alloy or a mixture of powders of the indicated components at the following ratio , wt.%. Cesium or rubidium aluminosilicate 0.5-25 NikelOstalnogo (L SP 9d; D

Description

2. A method of making a cold cathode by fixing the emission material on the core and activating it, characterized in that the mixture of powders of cesium aluminosilicate or rubidium and nickel is applied to the core, and the activation of the cathode is carried out at a temperature of 1100-1600 K for 5-30 minutes .

3, Method of making a cold cathode by fixing the emission material on the core and activating, characterized in that the mixture of powders of cesium or rubidium aluminosilicate and nickel is pressed and sintered at a temperature of 1000-1500 K for 10-50 minutes, the resulting alloy is made cathode , and activation is performed at a temperature of 1100 - 1600 K for 5-30 minutes.

The invention relates to the field of emission electronics, in particular, to the composition of the material for cold cathodes, which can be used as a source of electrons in electrovacuum devices, mainly in gas discharge devices of various types.

A known material for a cold tungsten-based cathode, the disadvantages of which are low emission. the ability is due to the large electron work function (, 53 eV), and the cost is high.

Also known is a method of making a cathode, according to which, to reduce the work function, the tungsten cathodes after installation in the device are covered with a film of cesium. At the same time, the work function decreases to a value (1.36 eV, which is not enough to provide a high emissivity.

A material for nickel-based cold cathodes and a method for its manufacture are also known when the cathode, after mounting in the instrument, is covered with a film of cesium sprayed from a special source placed in the same instrument. The cesium film reduces the work function of the nickel cathode to a value of (, 5 eV, which ensures the emission ability of the cathodes at a level of 10 -10 mA / cm, i.e. it remains at a relatively low level.

In addition, the disadvantage of the described Hijix cathodes and methods is

the complexity of the exact dosage of cesium in the process of its deposition on the surface of the cathode. Accurate dosage is necessary due to the fact that the emissivity of the latter depends on the amount of cesium on the cathode surface. These technological difficulties impede the use of such cathodes in industrial devices.

Among the known materials for cold cathodes, cesium or rubidium aluminosilicate has the highest emissivity, which, after special treatment, allows to obtain high current densities, selected as a prototype. There is also known a method of making a cold cathode by fixing the emission material on the core, activating at a temperature of 1200-1400 K and quenching to obtain the necessary porosity.

5 The disadvantage of this material is the inability of the cathodes made from it to work under conditions of intense ion bombardment. It was established experimentally that

cold cathodes based on aluminosilicate cesium or rubidium operate at pressures less than 10 mm Hg. With

 four

pressure of 10 mm Hg and above, these cathodes are completely deactivated. For this reason, they cannot be used in devices such as gas discharge, where the pressure of the working gas is hundreds of millimeters of mercury column. 31 An object of the invention is to provide a material for cold cathodes and a method for manufacturing cathodes, ensuring their stable operation under conditions of intense ion bombardment. To achieve this goal, the material comprising cesium or rubidium aluminosilicate, additionally contains nickel and consists of an alloy or a mixture of powders of the indicated components in the following ratio, wt%: Cesium or rubidium aluminosilicate 0.5-25 Nickel The Other Purpose is achieved by making a cold cathode by fixing the emission material at the core. and activation, according to which a mixture of powders of aluminosilicate cesium or rubidium and nickel is applied to the core, and the activation is carried out at a temperature of 1100-1600 K for 5-30 minutes. A variant of the method is possible, according to which a mixture of powders of cesium or rubidium aluminum silicate and nickel is pressed and sintered at a temperature of 1000–1500 K for 10–40 min, the cathode is made of the resulting alloy, and activation is performed at a temperature of 1100–1600 K for 5-30 minutes The cathodes of the material of the proposed composition, which is a mixture of powders of these components, are made by applying this mixture on a metal substrate by any known method, for example, pressing it onto a substrate that has a mold tube or a cup, sprayed suspension, etc. After mounting in the device, the cathode is heated to a temperature of 1100–1600 K, at which the exposure is carried out for 5–30 min, depending on the ratio of the components in the mixture. In tab. 1 shows the optimal exposure regimes for various specific material compositions. The holding mode dp of this composition of the mixture can be varied, so that for a mixture composition of 15 wt.% Aluminosilicate and 85 wt.% Nickel, activation can be carried out both at temperatures below 1400 K and more, however, the residence time should be increased accordingly or reduce. In the process of heat treatment in the specified mode, the formation of an alloy of nickel aluminosilicate cesium (rubidium) with simultaneous activation of the cathode. The proposed material can be obtained in the form of an alloy prior to mounting the cathode in the device. For this, a mixture of powders of nickel and aluminosilicate cesium or rubidium is pressed and sintered at a temperature of 1000-1500K for 10-50 minutes. In the table. Table 2 shows the optimum pressing and sintering conditions for mixtures with different content of components, which provide alloys that are close in their plastic properties to the properties of pure nickel. The sintering temperature and the holding time dp of this alloy composition can be varied by following the following pattern: with a decrease in sintering temperature, the holding time should be extended, and with increasing sintering temperature, the holding time should be reduced. In this case, the maximum sintering temperature should not exceed 1600 K, since this can lead to a change in the phase composition due to the fact that, starting from K, there is a noticeable evaporation of nickel. The alloys obtained in this way can be forged, stamped, rolled, etc., therefore, the technology for producing cathodes from such alloys does not differ from the technology for producing cathodes from pure nickel or from other plastic metals. In addition, cathodes based on the proposed alloy of nickel aluminosilicate cesium can be manufactured using technological techniques that are used in powder metallurgy, namely, by pressing a mixture of powders to obtain the desired configuration of the cathode and subsequent sintering of the compacted mass in accordance with the regimes in Table. 2. The cathode, made of an alloy of this composition, after mounting in the device, is activated in accordance with the modes given in Table 1. FIG. Figure 1 shows the experimentally obtained dependence of the current density of cathodes made of this material on the content of aluminosilicate in it. Measurements were carried out at room temperature and electric field intensity .W / cm. From FIG. I can see that the selected emission current for a composition of 0.5 wt.% Cesium aluminosilicate, 99.5 wt.% Nickel is equal to millimeters per centimeter squared, with an increase in the content of cesium aluminosilicate to 5 wt.% Emission current increases slightly, then the emission current rises sharply and reaches its maximum value at 15% by weight of cesium aluminosilicate. A further increase in the content of cesium aluminosilicate in the material leads to a decrease in the current taken. Given in FIG. 1 values of emission currents for compositions with cesium aluminosilicate content of 0.5, 15 and 25 wt.% Correspond to the effective work functions of 0.89.0.67 and 0.77 eV. It has been established that when the content of cesium aluminosilicate is less than 0.5 wt.%, The selected emission currents did not exceed thousand fractions of milliamperes per meter in square, therefore such coefficients will obviously not be of practical interest. With a cesium aluminosilicate content of more than 25 wt.%, The selected emission currents are x and tens of milliamperes per centimeter squared, but the components of the mixture do not form an alloy and the material is loose, which makes it unsuitable for practical use under conditions of intense ion bombardment, For a material containing rubidium aluminosilicate., the dependence of current density on composition has a similar appearance, with the absolute values of emission currents for particular compositions slightly lower compared to the data shown in FIG. 1. For a material containing 10 and 25 wt.% Rubidium aluminosilicate, the current density at V / cm, respectively, is 3 mA / cm and 2 mA / cm. FIG. 2, shows the temperature dependences of the electron current density of a cathode made of this material with a content of 15 wt.% Cesium aluminosilicate. Curve 1 was obtained with the electric field intensity, 5–10 V / cm, curve 2 — with the intensity E 2 “10 V / cm. FIG. 2, it can be seen that the proposed material makes it possible to remove high emission currents at a cathode temperature of from room temperature (300 K) to 400-500 K. The high emissivity of the material in the specified temperature range will ensure efficient operation of cathodes made from it in gas discharge devices, where In the discharge process, temperature can develop in the cathode - 400-500 K. In FIG. 3 shows the experimentally obtained volt-ampere ha; the characteristic of the cathode made of this material with a cesium aluminosilicate content of 15 wt.%. The characteristic was taken at the cathode room temperature. FIG. 3, it can be seen that the electron current of the cathode changes with an increase in anode voltage in accordance with the law characteristic of field emission. Cathodes made from this material with different content of alkali metal aluminosilicate (0.5, 15 and 25 wt.%) Were tested under gas discharge conditions in the forced mode. The test conditions were as follows: xenon gas, pressure 600 mm Hg st., ignition voltage 250 V, current taken 300 A, electrode spacing 37 mm. After 1000 pulses at a pulse frequency of 0.3 Hz, no changes in the parameters of the cathodes were observed. Thus, this material ensures stable operation of cathodes made from it under conditions of intense ion bombardment and has a fairly high emissivity. At present, the most efficient and technologically advanced material for cold cathodes, manufactured by industry and used in serial gas discharge devices, is tungsten with a rare earth additive. The yield of this material is tp - 2.2 eV. This material has an Lf work function, 2.5–3 times less. 71 and, accordingly, a higher emissivity. Due to this, the use of this material for cathodes of gas-discharge devices instead of tungsten used at the present time with these additives will reduce the ignition voltage in the devices by 2.5-3 times, which will significantly increase their efficiency, in particular, will create miniature pulses lamps with limited current for automatic photo flash.

Table 1 98 A significant economic effect should be expected due to a decrease in labor intensity in assembling cathode assemblies, since laser welding of the emitter with the core is eliminated and replaced by simple compression on the core. The advantage of this material is also the simplicity of the technology of its preparation, the use of non-deficient materials, the possibility of making from it cathodes of various configurations. j, HA / Cff I. t t 600 t too Phi I t woo iwo c

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Claims (3)

1. Material for the cold cathode of electronic devices, including cesium or rubidium aluminosilicate, characterized in that, in order to ensure the stable operation of the cathodes under conditions of intense ion bombardment, it additionally contains nickel and consists of an alloy or a mixture of powders of these components in the following ratio , wt.%, Cesium or rubidium aluminum silicate 0.5-25 Nickel Else Q ss SU ,,, 1115619 2. A method of manufacturing a cold cathode by fixing the emission material on the core and activating, characterized in that a mixture of cesium aluminosilicate or rubidium and nickel powders is applied to the core, and the cathode is activated at a temperature of 1100-1600 K for 5-30 minutes. 3. A method of manufacturing a cold cathode by fixing emission material on a core and activating, characterized in that the mixture of cesium or rubidium aluminosilicate powders and nickel is pressed and sintered at a temperature of 1000-1500 K for 10-50 minutes, from the obtained alloy a cathode is fabricated, and activation is performed at a temperature of 1100 - 1600 K for 5-30 minutes.