Lanthanum Hexaboride (LaB6) cathodes:

1. **Material Composition:**
- LaB6 is composed of lanthanum (La) and boron (B) in a hexaboride crystal structure.
- The hexaboride structure provides stability and high melting point, crucial for cathode applications.

2. **Electron Emissivity:**
- LaB6 is known for its exceptional electron emissivity, meaning it can efficiently release electrons when heated.
- This property is crucial for generating a high-intensity electron beam, essential in electron microscopy.

3. **Thermionic Emission:**
- The cathode operates based on thermionic emission, where electrons are released as a result of thermal excitation.
- When the cathode is heated to a certain temperature, electrons gain sufficient energy to overcome the work function and escape into free space.

4. **Temperature and Stability:**
- The cathode typically operates at temperatures ranging from 1400 to 2200 degrees Celsius.
- LaB6 exhibits good thermal stability, allowing for reliable and sustained electron emission over extended periods.

5. **Longevity:**
- One of the key advantages of LaB6 cathodes is their long lifespan compared to alternative cathode materials.
- This longevity contributes to the overall stability and reliability of electron microscopes.

6. **Electron Microscopy Applications:**
- LaB6 cathodes are widely used in transmission electron microscopes (TEM) and scanning electron microscopes (SEM).
- The high-quality electron beam produced by LaB6 enables detailed imaging and analysis of specimens at the microscopic level.

7. **Evaporation Coating:**
- LaB6 cathodes are sometimes used as a source material for thin film deposition through physical vapor deposition (PVD) techniques.

Understanding these detailed characteristics of LaB6 cathodes underscores their significance in electron microscopy and related applications.