Factors Affecting the Long-Term Stability of Barium Tungsten Electrodes

The factors affecting the long-term stability of barium tungsten electrodes and their mechanisms of action are as follows:

1. Material Composition

1.1 Barium-Tungsten Ratio:

Influence: The barium content directly affects the electron emission efficiency and surface stability. A moderate amount of barium can reduce the work function, but an excessive amount will lead to uneven surface distribution and accelerate oxidation or volatilization.

Mechanism: Barium and tungsten form compounds (such as BaWO₄), and optimizing the ratio can balance the emission performance and structural stability.

1.2 Rare Earth Element Doping

Influence: Elements such as lanthanum and cerium can refine the grains, reduce grain boundary defects, and enhance surface density.

Mechanism: By inhibiting grain growth, the high-temperature degradation process is delayed.

2. Preparation Process

2.1 Sintering Process

Influence: Temperature gradient and atmosphere control affect the diffusion fusion and density of barium tungsten.

Mechanism: Reasonable sintering process can promote compound formation and improve electrode density.

2.2 Impregnation and Activation Technology

Influence: The formation of the emission layer and the application of the activator affect the long-term emission performance.

Mechanism: The impregnation process forms a "reserve" barium ion diffusion layer, and the activator (such as zirconium hydride) promotes the release of barium ions.

3. Working Environment

3.1 Temperature and Atmosphere

Influence: High temperature accelerates the volatilization of barium, and the oxygen-containing environment leads to the formation of oxide film (such as BaO/Ba(OH)₂).

Mechanism: Inert gas (such as argon) protection can slow down oxidation, and high vacuum environment controls the volatilization rate of barium.

3.2 Mechanical and Thermal Stress

Influence: Thermal cycling and mechanical vibration lead to structural fatigue.

Mechanism: Optimizing the electrode shape (such as spiral structure) can reduce stress concentration and extend service life.

4. Electrochemical Performance

4.1 Electron Emission Mechanism

Influence: The balance between thermal ion emission and field emission affects stability.

Mechanism: At high temperatures, the thermal vibration of barium atoms dominates the emission, while at low temperatures, the electric field assists the emission to enhance stability.

4.2 Corrosion and Poisoning Effects

Influence: Acidic/alkaline environments or residual gases (such as CO₂) cause the barium component to dissolve or generate BaCO₃.

Mechanism: Corrosion products increase surface resistance and reduce emission current.

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