Alumina Ceramic Composition for Low Secondary Electron Emission
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Solution Overview
Problem
High frequency generators and plasma generators face issues with dielectric loss and secondary electron emission from alumina materials, leading to multipactor discharge and material degradation, which conventional TiN films cannot adequately address due to their limited durability and environmental sensitivity.
Innovation Solution
Alumina ceramic components with specific additives such as alkaline earth metals and elements from period 3, 4, or 5, which have higher first ionization energy than aluminum, are used to reduce secondary electron emission by optimizing grain size and structure, resulting in a lower secondary electron emission coefficient and improved plasma resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If alumina material is used for high frequency generator components, then low dielectric loss is achieved, but secondary electron emission occurs leading to multipactor discharge and material degradation
Solution Approach 1:
A TiN film coating is applied as an intermediary layer on the alumina material surface. This coating layer has low secondary electron emission characteristics and acts as a mediator to prevent electron emission from the alumina surface, thereby suppressing multipactor discharge while maintaining the low dielectric loss properties of the underlying alumina material
Solution Approach 2:
The invention creates a composite structure combining alumina material with a TiN film coating. This composite material integrates the low dielectric loss property of alumina with the low secondary electron emission property of TiN, achieving both requirements simultaneously
2Object-generated harmful factors
If TiN film is applied to suppress secondary electron emission, then multipactor discharge is mitigated, but the film deteriorates over time causing noise and pollution
Solution Approach 1:
The invention optimizes the thickness parameter of the TiN film coating to be within 1-10 micrometers. This parameter optimization ensures sufficient durability against deterioration while maintaining effective suppression of secondary electron emission, preventing both multipactor discharge and long-term degradation issues
3Loss of energy
If sapphire is used to achieve lower dielectric loss, then dielectric loss is reduced, but cost increases and strength decreases
Solution Approach 1:
The invention modifies the alumina material composition by adding specific sintering aids and controlling grain growth parameters to achieve grain sizes of 10 micrometers or more. These parameter changes enable polycrystalline alumina to achieve dielectric loss characteristics comparable to sapphire while maintaining the strength advantages of polycrystalline structures
Solution Approach 2:
The invention uses conventional alumina material with added sintering aids as a cost-effective alternative to expensive sapphire. By optimizing processing parameters to achieve large grain sizes, the invention achieves comparable electrical performance at lower cost and with superior mechanical strength properties
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 alumina ceramic components exhibit reduced secondary electron emission and enhanced durability, suitable for high frequency and plasma applications, including waveguides and industrial machinery, with improved resistance to electrical discharge and environmental factors.
Implementation Method 1
electrons are emitted from the alumina material due to the discharge phenomenon inside the device, which leads to local degeneration called multipactor on the surface of the alumina material
Implementation Method 2
Both of the alkaline earth metal and the element belonging to period 3, 4 or 5 have a higher first ionization energy than aluminum
Implementation Method 3
a ratio (x/y) of the grain boundary area (x) to the grain area (y) in the alumina ceramic is 0.0001 to 0.001
Data Source
AI summary
Provided is an alumina ceramic with a low secondary electron emission coefficient and suitable for components of a high frequency generator, a plasma generator and so on. The alumina ceramic contains alumina as a main component, and at least two kinds of elements selected from an alkaline earth metal and from an element belonging to period 3, 4 or 5. The alkaline earth metal and the element belonging to period 3, 4 or 5 have a higher first ionization energy than aluminum. An electronegativity difference between the alkaline earth metal and the element belonging to period 3, 4 or 5 is 0 or more and 0.6 or less. A ratio (x/y) of the grain boundary area (x) to the grain area (y) in the alumina ceramic is 0.0001 to 0.001.