Cathode for electron tube
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsMasato Saito, Keiji Fukuyama, Masako Ishida, Keiji Watanabe, Toyokazu Kamata, Kinjiro Sano
Life of this patent
Estimating the term…
Abstract
This invention is a cathode of an indirect heated type having improved electron emission characteristics. A cathode for an electron tube in accordance with the present invention comprises: a base containing Ni as a major element; and a layer of an electron-emissive substance formed on the base, this layer comprising not only alkaline earth metal oxide as a principal component containing at least Ba, but also rare earth metal oxide of 0.1 to 20 wt. % or rare earth metal of 0.05 to 15 wt. %.
Claims30
An oxide-coated thermionic cathode for an electron tube, comprising:
- a base comprising Ni as a major element, said base having a outer surface;
- a reducing agent contained in said base;
- only at least a portion of said outer surface of said base having coated thereon an electron-emisive substance comprising (a) an alkaline earth metal oxide as a principal component including barium oxide, and (b) 0.1 to 20 wt. % of at least one rare earth metal oxide selected from the group consisting of the oxides of Y, La, Ce, Pr, Nd, Sm, Gd, Sc, Dy, Ho, Er and Tm, and
- a heater for heating said layer.
An oxide-coated thermionic cathode for an electron tube, comprising;
- a base comprising Ni as a major element, said base having an outer surface;
- reducing agent contained in said base;
- only at least a portion of said outer surface of said base having coated thereon an electron-emissive substance comprising (a) an alkaline earth metal oxide as a principal component including a barium oxide, and (b) 0.05 to 15 wt. % of at least one rare earth metal selected form the group consisting of the oxides of Y, La, Ce, Pr, Nd, Sm, Gd, Sc, Dy, Ho, Er and Tm, and
- a heater for heating said layer.
An oxide-coated cathode for an electron tube, comprising:
- a base comprising Ni as a major element and a reducing agent, said base having an outer surface;
- a rare earth metal oxide layer of less than 10 .mu.m in thickness coated on at least a portion of said outer surface of said base, said rare earth metal oxide selected form the group consisting of at least one of the oxides of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er and Tm, and
- a layer of an electron-emissive substance formed on said rare earth metal oxide layer and comprising alkaline earth metal oxide containing at leat Ba.
An oxide-coated cathode for an electron tube, comprising:
- a base comprising Ni as a major element and a reducing agent, said base having an outer surface;
- a rare earth metal layer of less than 6 .mu.m in thickness coated on at least a portion of said outer surface of said base, said rare earth metal being selected from the group consisting of at least one of the oxides of Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er and Tm, and
- a layer of an electron-emissive substance formed on said rare earth metal layer and comprising alkaline earth metal oxide containing at least Ba.
An oxide-coated thermionic cathode for an electron tube, comprising:
- a base containing Ni and a reducing agent, said base having an outer surface;
- and
- a layer of an electron-emissive substance coated on at least a portion of said outer srface of said base, said electron-emissive layer comprising a mixture of a powder of a rare earth metal oxide containing at least one of the oxides of Y, La, Ce, Pr, Nd, Sm, Gd, Sc, Dy, Ho, Er and Tm and an alkaline earth metal carbonate powder, said mixture being applied as a suspension containing said rare earth metal oxide powder and said alkaline earth metal carbonate powder to form said electron-emissive substance.
In an oxide-coated thermionic cathode for an electron tube, wherein a layer of an electron-emissive substance comprising an oxide of an alkaline earth metal including Ba is formed on the surface of a base comprising Ni and at least one reducing agent, and wherein free Ba is produced by reduction of said alkaline earth metal oxide by said at least one reducing agent, and wherein an interface layer containing an oxide of said at least one reducing agent is formed betwee said base and said electron-emissive layer as a result of partial reduction of said alkaline earth metal oxide layer which reduces an electron-emission characteristic of said cathode by limiting production of free Ba in said cathode:
- the improved cathode wherein an electron-emission characteristic of said cathode is enhanced by including in said layer a rare earth metal oxide containing at least one of the oxides of Y, La, Ce, Pr, Nd, Sm, Gd, Sc, Dy, Ho, Er and Tm in admixture with said alkaline earth metal oxide.
In an oxide-coated cathode for an electron tube comprising a base having a outer surface and comprising nickel as a major element, a reducing agent contained in said base, wherein only at least a portion of said outer surface of said base has coated thereon an electron emissive substance including an alkaline earth metal oxide as a principal component including barium oxide, free barium being produced by reduction of said alkaline earth metal oxide by said at least one reducing agent and wherein an interface layer containing an oxide of said at least one reducing agent between said base and said electron-emissive layer formed as a result of partial reduction of said alkaline earth metal oxide layer reduces an electron-emission characteristc of said cathode by limiting production of free barium in said cathode;
- the improvement for extending a lifetime of said cathode at an enhanced current density operation thereof by preventing or inhibiting formation of said interface layer, comprising 0.1 to 20 wt. % of at least one rare earth metal oxide selected from the group consisting of the oxides of Y, La, Ce, Pr, Nd, Sm, Gd, Sc, Dy, Ho, Br and Tm, contained in admixture with said alkaline earth metal oxide in said electron emissive substance.
Dependencies are inferred from the claim text.