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Electron Microscopy Sciences

Technical Data Sheets

Comparing Lanthanum Hexaboride (LaB6) and Cerium Hexaboride (CeB6) Cathodes

EMS Catalog #80920 - 80933

The performance and lifetime of the hexaboride cathode are determined by several factors: vacuum level, cathode temperature, impurity level, crystal orientation, tip shape, and mount design.

CeB6 exhibits a lower evaporation rate

CeB6 has an evaporation rate at normal operating temperatures near 1800 K that is lower than that of LaB6 . So long as care is taken to operate the cathode below 1850 K, CeB6 should maintain an optimum tip shape longer, and therefore last longer.

Evaporation Rate Comparison
Evaporation Rate Comparison for LaB6 and CeBix™ at 2 x 10-8 Torr

CeB6 is more resistant to carbon contamination

In laboratory tests, CeB6 has proven to be more resistant to the negative impact of carbon contamination than LaB6. This increases stability and results in less time to reach stable operation and more rapid recovery from contamination events.


Recovery from Carbon Contamination Comparison between LaB6 and CeBix

 


Carbon Contamination Comparison between LaB6 and CeBix

Reduced effects of O2 on CeBix

The effects on oxygen on current density is shown in the figures below for LaB6 and CeBix.

Material Data for LaB6 and CeB6

Parameter
Units LaB6 CeB6
Stoichiometry
N/A
~6
Metal Impurities
ppm by wt.
<30
Density
g/cm3
4.72
4.80
Coefficient of Thermal Expansion
α x 106
5.6
6.2
Electrical Resistivity
µΩ-cm
~50
~65
Effective Work Function (100) at 1800 K
eV
2.70
2.65
Spectral Emissivity at 0.65 microns
N/A
0.765
0.779
Evaporation rate at 1800 K (UHV)
g/cm2/s
2.2 x 10-9
1.6 x 10-9
Orientation limit for specific orientation
degrees
<2
Pyrolitic block mount resistance @ 1800 K
Ohms
1.45

 

Online Ordering

Lanthanum Hexaboride (LaB6) and Cerium Hexaboride (CeB6) Cathodes are available online from the EMS Catalog. For ordering or product information, click here.