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  6. Material Data:Transition Metal Carbide Cathodes(遷移金属炭化物電子源)

Material Data:Transition Metal Carbide Cathodes(遷移金属炭化物電子源)

Parameter Units HfC ZrC NbC TaC TiC VC
Molecular Weight g/mol 190.51 103.23 104.92 192.96 59.91  
Stoichiometry N/A ~1 ~1 ~1 ~1 ~1 ~1
Metal Impurities ppm by wt. <30 <30 <30 <30 <30 <30
Lattice Parameter Angstroms 4.64 4.7 4.468 4.454 4.328 4.16
Melting Temperature K ~4160 ~3300 ~3770 ~4150 ~3430  
Density g/cm3 12.2 6.59 7.79 14.5    
Hardness Kg/mm2   2600 2470 1800 3200  
Coefficient of Thermal Expansion @ 300-3000 K α × 10^6 7.3 ± 0.2 7.6 ± 0.2     9.5 ± 0.3  
Thermal Conductivity cal-cm/(s-cm2-C)   0.049 0.034 0.053 0.049  
Electrical Resistivity µΩ-cm 109 ~70 74 170-200 180-250  
Effective Work Function (100) at 1800 K eV 3.58 3.53 4.00 4.20 3.80  
Absolute Work Function (100) at 300 K eV   3.5     4.12  
Spectral Emissivity (@ 0.65 microns & 2000 K) N/A 0.645 0.48 0.359 0.365 0.487 0.433
Evaporation rate at 1800 K (UHV) g/cm2/s <10^-9 <10^-9        
Orientation limit for specific orientation degrees <2 <2 <2 <2 <2 <2