Carburized La2O3 Lu2O3 Co-doped Mo Cathode Emission Stability
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Solution Overview
Problem
ThO2-W thermionic cathodes have poor ductility and low yield, and La2O3-Mo cathodes exhibit poor emission stability, limiting their application in magnetrons, particularly in microwave oven equipment.
Innovation Solution
A carburized La2O3 and Lu2O3 co-doped Mo filament cathode is developed using a method involving the mixing of La(NO3)3, Lu(NO3)3, and Mo powders, followed by calcination, pressing, sintering, and carburization at high temperatures to enhance thermal emission properties and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If ThO2-W thermionic cathode is used, then thermal emission property is improved, but ductility and manufacturing yield deteriorate
Solution Approach 1:
The patent uses composite materials by combining Mo base metal with La2O3 and Lu2O3 rare earth oxides to create a cathode that achieves both high thermal emission properties and good ductility. The composite structure allows the material to exhibit enhanced electron emission while maintaining mechanical workability, resolving the contradiction between emission performance and manufacturability.
2Ease of manufacture
If La2O3-Mo cathode is used, then manufacturing ease is improved, but emission stability deteriorates
Solution Approach 1:
The patent creates a composite material system combining La2O3-Mo with Lu2O3 doping. This composite approach maintains the manufacturing advantages of La2O3-Mo while Lu2O3 provides the missing electron supplementation mechanism, thereby achieving both ease of manufacture and emission stability required for magnetron applications.
Solution Approach 2:
The patent applies local quality by selectively doping specific regions or phases with Lu2O3 within the La2O3-Mo matrix. This localized enhancement of secondary electron emission properties in critical areas maintains overall manufacturing simplicity while providing the necessary emission stability through targeted material modification.
3Reliability
If high temperature carbonization treatment is applied, then emission stability is improved, but energy consumption increases
Solution Approach 1:
The patent optimizes the carbonization treatment parameters including temperature, time, and atmosphere composition to achieve the required emission stability with minimized energy consumption. By precisely controlling these parameters, the cathode attains sufficient carbonization degree for stable electron emission without excessive energy input, resolving the contradiction between emission stability and energy efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The carburized La2O3 and Lu2O3 co-doped Mo filament cathode achieves high thermal emission properties and stability, with an emission current approximately twice that of ThO2-W cathodes and a lifetime exceeding 500 hours, suitable for microwave oven applications.
Implementation Method 1
Active substances, La2O3 and Lu2O3, can improve the thermal emission property and emission stability of the cathode
Implementation Method 2
A method of carburization treatment of the La2O3 and Lu2O3 co-doped Mo filament cathode
Data Source
AI summary
A carburized La2O3 and Lu2O3 co-doped Mo filament cathode is made from lanthanum oxide (La2O3) and lutetium oxide (Lu2O3) doped molybdenum (Mo) powders, the lanthanum oxide (La2O3) and lutetium oxide (Lu2O3) doped molybdenum (Mo) powders contain La2O3, Lu2O3 and Mo with the total concentration of La2O3 and Lu2O3 being 2.0-5.0 wt. % and the rest being Mo.