Patent Application
20130105742
This application claims priority to Chinese Patent Application No. 201110341108.3, filed Nov. 2, 2011, which is incorporated in its entirety herein by reference.
The present disclosure relates to a method of manufacturing an impregnated yttric or gadolinium-containing Barium-aluminum-scandate cathode with yttrium oxide/gadolinium oxide-tungsten matrix, which belongs to the technical field of rare earth-refractory metal cathodes.
Magnetrons, as an important kind of high power microwave devices, have a wide range of applications in many fields, such as military, medical and civil fields. As one of the key components of the magnetron, the cathode plays an important role in the operation of magnetrons. In order to develop high-power and high-frequency magnetrons, the cathodes are needed to have a certain thermionic emission and excellent secondary electron emission properties. Currently, Ba—W dispenser cathodes are generally used in the commercial magnetrons. However, Ba—W dispenser cathodes can not fulfill the requirements of the high power magnetrons due to their bad anti-bombarding insensitivity and poor secondary emission yields. It has been shown that REO-Mo cathodes exhibit an excellent secondary emission property and good anti-bombarding insensitivity. However, their low thermionic emission current density still limits their applications in the high power magnetrons. Therefore, there remains a need for developing a new type of cathodes possessing all desired properties for high power and millimeter-wave magnetron applications.
The present disclosure provides an impregnated rare earth containing Barium aluminum-scandate cathode with a rare earth oxide doped tungsten matrix and methods for the fabrication.
In one aspect, an impregnated rare earth-containing Barium-aluminum-scandate cathode may comprise a first rare earth oxide doped tungsten matrix; and an impregnated active substance. The impregnated active substance may comprise scandium oxide (Sc2O3), a second rare earth oxide, and Barium-calcium-aluminate, wherein the molar ratio of Ba:Ca:Al is about 4:1:1.
In some embodiments, the concentration of the first rare earth oxide in the matrix ranges from 3 to 10% by weight.
In some embodiments, the first rare earth oxide in the matrix is yttrium oxide (Y2O3) or gadolinium oxide (Gd2O3).
In some embodiments, the concentration of the Sc2O3 in the impregnated active substance ranges from 2 to 6% by weight.
In some embodiments, the concentration of the second rare earth oxide in the impregnated active substance ranges from 3 to 5% by weight.
In some embodiments, the second rare earth oxide in the impregnated active substance is Y2O3, or Gd2O3.
In another aspect, an impregnated rare earth-containing Barium-aluminum-scandate cathode may comprise a first rare earth oxide doped tungsten matrix; and an impregnated active substance that comprises scandium oxide (Sc2O3), a second rare earth oxide, and Barium-calcium-aluminate; wherein the first and the second rare earth oxides are yttrium oxide (Y2O3) or gadolinium oxide (Gd2O3);
In some embodiments, the concentration of the first rare earth oxide in the matrix ranges from 3 to 10% by weight.
In some embodiments, the impregnated active substance comprises 2 to 6% in weight of Sc2O3, 3 to 5% by weight of Y2O3 or Gd2O3, and Barium-calcium-aluminate in the molar ratio of Ba:Ca:Al of 4:1:1.
In another aspect, a method for making the impregnated rare earth-containing Barium-aluminum-scandate cathodes may comprises: mixing a rare earth oxide with a tungsten powder; pressing the mixed powder into pellets under a pressure between 1.5 t/cm2 to 4 t/cm2; sintering the pellet under hydrogen at a temperature between 1500° C. and 1600° C. for 10 to 20 minutes to obtain a matrix; dissolving a raw material comprising scandium nitrate, Barium nitrate, calcium nitrate, aluminum nitrate, and rare earth nitrate in de-ionized water to obtain a raw material solution; titrating an excess amount of aqueous ammonium carbonate solution into the raw material solution until all cations are precipitated out; leaching the precipitated solid; drying the solid; calcining the dried solid under air/oxygen at a temperature between 650° C. and 950° C. for 2 to 5 hours; reacting the calcined solid under dry hydrogen at a temperature between 1500° C. and 1600° C. for 10 to 30 minutes to obtain an impregnated active substance; and impregnating the active substance into the matrix under hydrogen at a temperature between 1600° C. and 1650° C. for 1 to 3 minutes.
In some embodiments, the concentration of the rare earth oxide in the matrix ranges from 3 to 10% by weight.
In some embodiments, the rare earth oxide in the matrix is yttrium oxide (Y2O3) or gadolinium oxide (Gd2O3).
In some embodiments, the rare earth nitrate is yttrium nitrate, or gadolinium nitrate.
In some embodiments, the raw materials correspond to 2 to 6% by weight of Sc2O3, 3 to 5% by weight of Y2O3 or Gd2O3, and Barium-calcium-aluminates in the molar ratio of Ba:Ca:Al of 4:1:1.
In another aspect, a method for making a rare earth oxide doped tungsten matrix may comprise: mixing a rare earth oxide power and a tungsten powder; pressing the mixed powders into pellets; and sintering the pellet to obtain a matrix.
In some embodiments, the concentration of the rare earth oxide ranges from 3 to 10% by weight.
In some embodiments, the rare earth oxide powder and the tungsten power are mixed by mechanical mixing method.
In some embodiments, the rare earth oxide is yttrium oxide (Y2O3), or gadolinium oxide (Gd2O3).
In some embodiments, the mixed powders are pressed under a pressure between 1.5 t/cm2 to 4 t/cm2 to form pellets.
In some embodiments, the pellet is sintered under hydrogen at a temperature between 1500° C. and 1600° C. for 10 to 20 minutes.
In another aspect, a method for making an impregnated active substance may comprise: dissolving raw materials comprising scandium nitrate, barium nitrate, calcium nitrate, aluminum nitrate, and rare earth nitrate in de-ionized water to obtain a raw material solution; titrating an excess amount of aqueous ammonium carbonate solution into the raw material solution until all cations are precipitated out; leaching the precipitated solid from the solution; drying the solid; calcining the dried solid; and reacting the calcined solid under dry hydrogen to form an impregnated active substance.
In some embodiments, the rare earth nitrate is yttrium nitrate, or gadolinium nitrate.
In some embodiments, the raw materials correspond to 2 to 6% by weight of Sc2O3, 3 to 5% by weight of Y2O3 or Gd2O3, and Barium-calcium-aluminate in the molar ratio of Ba:Ca:Al of 4:1:1
In some embodiments, the solid is calcined under air/oxygen at a temperature between 650° C. and 950° C. for 2 to 5 hours
In some embodiments, the solid is reacted under dry hydrogen at temperatures between 1500° C. and 1600° C. for 10 to 30 minutes.
In yet another aspect, a method for making an impregnated rare earth-containing Barium-aluminum-scandate cathode with a rare earth oxide doped tungsten matrix may comprises impregnating the active substance into the rare earth oxide doped tungsten matrix under hydrogen at a temperature between 1600° C. and 1650° C. for 1 to 3 minutes.
Thus, the present disclosure provides a method for fabricating an impregnated yttric or gadolinium-containing Barium-aluminum-scandate cathode with yttrium oxide (Y2O3)/gadolinium oxide (Gd2O3)-tungsten (W) matrix. The rare earth oxide Y2O3/Gd2O3 is doped into the matrix, and then the yttric or gadolinium-containing Barium-aluminum-scandate is impregnated into the matrix above in order to enhance the thermionic emission and secondary emission properties of the cathode.
There are a number of advantages provided by the techniques of the present disclosure. The impregnated yttric or gadolinium-containing Barium-aluminum-scandate cathode with yttrium oxide/gadolinium oxide-tungsten matrix provided by this present disclosure exhibits excellent secondary emission performance, i.e., the maximum secondary emission yield δmax of the cathode with 10 wt % content of Y2O3 in the matrix is 3.51, and the thermionic emission current density of this cathode at 900° C. can reach 20.99 A/cm2 after being activated. The maximum secondary emission yield δmax of the cathode with 10 wt % content of Gd2O3 in the matrix is 3.87, and the thermionic emission current density of this cathode at 900° C. can reach 19.36 A/cm2 after being activated. The performance of these two kinds of cathodes is better than that of Ba—W dispenser cathode used in the commercial magnetrons at present, which makes it possible for the practical application.
The techniques of the present disclosure will now be described in detail with reference to the accompanying drawings.
In the following description, impregnated rare earth-containing Barium-aluminum-scandate cathodes with a rare earth oxide doped tungsten matrices are obtained according to the present disclosure.
In some embodiments, the rare earth oxide is yttrium oxide (Y2O3), or gadolinium oxide (Gd2O3).
In some embodiments, the concentration of the rare earth oxide ranges from 3 to 10 wt %.
In some embodiments, the rare earth oxide powder and the tungsten power are mixed by mechanical mixing method.
In some embodiments, the rare earth oxide is yttrium oxide (Y2O3), or gadolinium oxide (Gd2O3).
In some embodiments, the mixed powders are pressed under a pressure between 1.5 t/cm2 to 4 t/cm2 to form pellets.
In some embodiments, the pellet is sintered under hydrogen at a temperature between 1500° C. and 1600° C. for 10 to 20 minutes.
In some embodiments, the rare earth nitrate is yttrium nitrate, or gadolinium nitrate.
In some embodiments, the raw materials correspond to 2 to 6 wt % of Sc2O3, 3 to 5 wt % of Y2O3 or Gd2O3, and Barium-calcium-aluminate in the molar ratio of Ba:Ca:Al of 4:1:1
In some embodiments, the solid is calcined under air/oxygen at a temperature between 650° C. and 950° C. for 2 to 5 hours
In some embodiments, the solid is reacted under dry hydrogen at temperatures between 1500° C. and 1600° C. for 10 to 30 minutes.
An impregnated rare earth-containing Barium-aluminum-scandate cathode with a rare earth oxide doped tungsten matrix can be obtained by impregnating the active substance into the rare earth oxide doped tungsten matrix under hydrogen at a temperature between 1600° C. and 1650° C. for 1 to 3 minutes.
The performance of rare earth-containing Barium-aluminum-scandate cathodes according to the present disclosure is evaluated and compared with that of conventional Ba—W dispenser cathode (
0.90 g of Y2O3 and 29.10 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ3×1.5 mm under the pressure of 4 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1500° C. for 10 minutes and shaped into the matrices needed. The aqueous solution of 3.11 g of Y(NO3)3.4H2O, 2.17 g of Sc(NO3)3.4H2O, 24.94 g of Ba(NO3)2, 5.63 g of Ca(NO3)2.4H2O, 17.90 g of Al(NO3)39H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 650° C. for 2 h, and then reacted in the dry hydrogen at 1500° C. for 10 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1600° C. for 1 minute, thus the impregnated yttric Barium-aluminum-scandate cathodes with yttrium oxide-tungsten matrices were obtained.
1.50 g of Y2O3 and 28.50 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 3 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1550° C. for 15 minutes and shaped into the matrices needed. The aqueous solution of 1.86 g of Y(NO3)3.4H2O, 1.44 g of Sc(NO3)3.4H2O, 25.75 g of Ba(NO3)2, 5.82 g of Ca(NO3)3.4H2O, 18.48 g of Al(NO3)3.9H2O, and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 750° C. for 3 h, and then reacted in the dry hydrogen at 1550° C. for 20 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1650° C. for 2 minutes, thus the impregnated yttric Barium-aluminum-scandate cathodes with yttrium oxide-tungsten matrices were obtained.
2.10 g of Y2O3 and 27.90 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 2 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1600° C. for 20 minutes and shaped into the matrix needed. The aqueous solution of 2.49 g of Y(NO3)3.4H2O, 2.89 g of Sc(NO3)3.4H2O, 24.94 g of Ba(NO3)2, 5.63 g of Ca(NO3)3.4H2O, 17.90 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 850° C. for 4 h, and then reacted in the dry hydrogen at 1600° C. for 30 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1650° C. for 3 minutes, thus the impregnated yttric Barium-aluminum-scandate cathodes with yttrium oxide-tungsten matrices were obtained.
2.70 g of Y2O3 and 27.30 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 1.5 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1500° C. for 15 minutes and shaped into the matrices needed. The aqueous solution of 2.49 g of Y(NO3)3.4H2O, 3.61 g of Sc(NO3)3.4H2O, 24.66 g of Ba(NO3)2, 5.57 g of Ca(NO3)3.4H2O, 17.70 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 950° C. for 5 h, and then reacted in the dry hydrogen at 1500° C. for 20 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1650° C. for 1 minute, thus the impregnated yttric Barium-aluminum-scandate cathodes with yttrium oxide-tungsten matrices were obtained.
3.00 g of Y2O3 and 27.00 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 4 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1550° C. for 10 minutes and shaped into the matrices needed. The aqueous solution of 1.86 g of Y(NO3)3.4H2O, 4.33 g of Sc(NO3)3.4H2O, 24.66 g of Ba(NO3)2, 5.57 g of Ca(NO3)2.4H2O, 17.70 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 700° C. for 4 h, and then reacted in the dry hydrogen at 1550° C. for 10 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1600° C. for 2 minutes, thus the impregnated yttric Barium-aluminum-scandate cathodes with yttrium oxide-tungsten matrices were obtained.
0.90 g of Gd2O3 and 29.10 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ3×1.5 mm under the pressure of 4 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1500° C. for 10 minutes and shaped into the matrices needed. The aqueous solution of 1.37 g of Gd(NO3)3.4H2O, 1.44 g of Sc(NO3)3.4H2O, 25.75 g of Ba(NO3)2, 5.82 g of Ca(NO3)2.4H2O, 18.48 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 650° C. for 2 h, and then reacted in the dry hydrogen at 1600° C. for 20 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1600° C. for 3 minutes, thus the impregnated gadolinium-containing Barium-aluminum-scandate cathodes with gadolinium oxide-tungsten matrices were obtained.
1.50 g of Gd2O3 and 28.50 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 3 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1550° C. for 15 minutes and shaped into the matrices needed. The aqueous solution of 1.83 g of Gd(NO3)3.4H2O, 2.17 g of Sc(NO3)3.4H2O, 25.21 g of Ba(NO3)2, 5.69 g of Ca(NO3)2.4H2O, 18.09 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 750° C. for 3 h, and then reacted in the dry hydrogen at 1600° C. for 10 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1600° C. for 1 minute, thus the impregnated gadolinium-containing Barium-aluminum-scandate cathodes with gadolinium oxide-tungsten matrices were obtained.
2.10 g of Gd2O3 and 27.90 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 2 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1600° C. for 20 minutes and shaped into the matrices needed. The aqueous solution of 2.29 g of Gd(NO3)3.4H2O, 2.89 g of Sc(NO3)3.4H2O, 24.66 g of Ba(NO3)2, 5.57 g of Ca(NO3)2.4H2O, 17.70 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 850° C. for 4 h, and then reacted in the dry hydrogen at 1500° C. for 30 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1650° C. for 2 minutes, thus the impregnated gadolinium-containing Barium-aluminum-scandate cathodes with gadolinium oxide-tungsten matrices were obtained.
2.70 g of Gd2O3 and 27.30 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 1.5 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1500° C. for 15 minutes and shaped into the matrices needed. The aqueous solution of 1.83 g of Gd(NO3)3.4H2O, 4.33 g of Sc(NO3)3.4H2O, 24.39 g of Ba(NO3)2, 5.51 g of Ca(NO3)2.4H2O, 17.51 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 950° C. for 5 h, and then reacted in the dry hydrogen at 1550° C. for 30 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1650° C. for 3 minutes, thus the impregnated gadolinium-containing Barium-aluminum-scandate cathodes with gadolinium oxide-tungsten matrices were obtained.
3.00 g of Gd2O3 and 27.00 g of W powders were mixed by a mechanical mixing method, and then the powders were pressed into the pellets with the size of φ10×1.5 mm under the pressure of 4 t/cm2. Finally, the pellets were sintered in the atmosphere of hydrogen at 1550° C. for 10 minutes and shaped into the matrices needed. The aqueous solution of 1.37 g of Gd(NO3)3.4H2O, 3.61 g of Sc(NO3)3.4H2O, 24.94 g of Ba(NO3)2, 5.63 g of Ca(NO3)2.4H2O, 17.90 g of Al(NO3)3.9H2O and 22.00 g of (NH4)2CO3 was dissolved in the de-ionized water, respectively. The aqueous solution of nitric salt prepared in the first step was mixed together, and then excessive ammonium carbonate solution was titrated into the mixed aqueous solution until all cations are precipitated out. After leaching and drying, the powders were calcined in the atmosphere of air/oxygen at 700° C. for 4 h, and then reacted in the dry hydrogen at 1600° C. for 20 minutes to obtain the active substance which is subsequently impregnated into the matrices above at the temperature of 1600° C. for 1 minute, thus the impregnated gadolinium-containing Barium-aluminum-scandate cathodes with gadolinium oxide-tungsten matrices were obtained.
The maximum secondary emission yield obtained from Examples 2-5 and 7-10 are summarized in Table 1.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201110341108.3 | Nov 2011 | CN | national |
