Data

Character table:

Boride character Table

  TiB2 ZrB2 TaB2 NbB2 WB MoB CrB LaB6
Boron content[%] 31.11 19.16 10.67 18.88 5.55 10.13 17.21 31.83
Crystal structure Hexagonal Hexagonal Hexagonal Hexagonal Tetragonal Tetragonal Orthorhombic Cubic
Lattice periods,kx. a 3.026 3.168 3.078 3.089 3.115 3.110 2.969 4.1561
b or c 3.213 3.528 3.265 3.303 16.93 16.97 b  7.858 C 3.002  
c/a 1.062 1.114 1.050 1.060 5.42 5.45    
Density[g/cm3]
calculated
4.530 6.09 12.62 7.00 15.734 8.665 6.11 4.722
experimental 4.38 6.17 12.38 6.97 ~15.4 8.3 6.05 4.76
Microhardness 30g
[kg/mm2]
3370±60 2252±22 2500±42 2600 3700(50g) 2350(50g) ~1300(100g) 2770±60
Melting Point[℃] 2790 3200 3037 3000 2800 2550 2100 2530
Heat of formation
ΔH°(298)[Kcal/mol]
-70.0 -76.7 -46 -59 -17 -16.3 (CrB2)  -30 -112.3
Entropy S°(298)
[Kcal/mol・℃]
7.52 10.7 13.9 10.4     5.8  
Specific electrical
resistance[μΩ・cm] at
20℃
9.0 9.7 32.5 25.7 ~22 45 45.5 15.0
Point of transition to
superconductivity °K
<1.28 <1.80 <1.28 <1.0 <1.28 <1.28 <1.28 5.7

(Reference) Hand book refractory compounds (metallurgiya in Moscow 1976 editions)

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