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Achieving High-Temperature Measurement Using Thermionic Emission from a W-La2O3 Cathode in Low-Pressure Argon Glow
Wei Liang1, Xinyu Zhang1,2, Jun Wang1,2
1Taihu Laboratory of Deepsea Technological Science, Wuxi 214000, China.
Materials (Basel, Switzerland)
|June 12, 2026
Summary
This study explores high-temperature measurements using thermionic emission from a W-La2O3 cathode in argon plasma. Optimizing discharge parameters allows for accurate temperature determination by balancing cooling and heating effects.
Area of Science:
- Materials Science
- Plasma Physics
- High-Temperature Measurement Techniques
Background:
- Thermionic emission from W-La2O3 cathodes is crucial for high-temperature applications.
- Plasma environments introduce complex interactions affecting cathode behavior compared to vacuum.
- Understanding the interplay of thermionic emission cooling (TEC) and ion bombardment heating (IBH) is key.
Purpose of the Study:
- To investigate the feasibility of high-temperature (2000-2200 °C) measurements using thermionic emission in a low-pressure argon glow discharge.
- To analyze the differences in cathode emission and temperature variation in plasma versus vacuum.
- To identify the critical discharge parameters influencing TEC and IBH effects.
Main Methods:
- Utilized a W-La2O3 cathode in a low-pressure argon glow discharge.
- Varied discharge parameters including bias voltage and background pressure.
- Analyzed cathode emission characteristics and temperature variation patterns.
- Applied the modified Schottky equation for temperature determination.
Main Results:
- Cathode emission and temperature patterns differ significantly in plasma compared to vacuum due to TEC and IBH.
- Applied bias voltage is the primary factor governing the balance between TEC and IBH.
- Identified three bias voltage regions: TEC-dominated (10-20 V), transition (20-40 V), and IBH-dominated (40-60 V).
- Mutual offset of TEC and IBH in the transition region enables unambiguous temperature determination.
Conclusions:
- High-temperature measurements (2000-2200 °C) are feasible in argon plasma by controlling TEC and IBH.
- Optimizing discharge parameters, particularly bias voltage, is essential for accurate thermionic emission-based temperature measurements.
- The modified Schottky equation, under balanced TEC/IBH conditions, simplifies the J-T relationship for reliable high-temperature quantification.
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