Office of Technology Transfer – University of Michigan

High Temperature Cathode Heater

Technology #5595

The following NPD does not include the main aspects of the invention, namely boron nitride and rhenium. It is thought the use of these words would disclose important information. However, omitting them has resulted in mildly unattractive wording in some cases, specifically in the heading.

A University of Michigan research team has developed a stable high-temperature cathode heater for electron emission applications. In systems driven by thermionic emission, materials must be heated above 1700° C to emit electrons; designing a heater at these temperatures is challenging. Low work function (~2.5 eV) materials, such as lanthanum hexaboride (LaB6), are often used to lower the operating temperature but introduce further problems with common heating materials. Conventional heaters composed of tungsten, with the highest melting point of any element, suffer from boron diffusion in these systems resulting in shortened lifespan and increased operating cost. The research team’s heater provides an alternative solution to this engineering problem with potential to increase heater stability and introduce cost savings in many applications including plasma propulsion and thin film semiconductor processing.

Stability Enhanced Hot Cathode with Simple Manufacture Using a boron diffusion inhibiting heater material, with high ductility and melting temperature, this cathode heater has been successfully demonstrated experimentally. It shows superior stability to thermal cycling with 100s of hours of operation and 200 W of power dissipation. The ductile material enables manufacture without specialized processes, which decreases processing costs and increases commercial potential while the use of a high thermal conductivity electrical insulator enables efficient heat transfer to the emitting material. With superior stability, operation and maintenance considerations, this design has potential to be competitive in many applications where high temperature operation is required.

Applications • Plasma Propulsion • Electron Microscopy • Thin Film Processing • Electron Beam Welding • High Temperature Heating

Advantages • Boron Stable • Ease of Manufacture • Thermal cycling endurance • Material compatibility