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PBN is an
anisotropic, high temperature ceramic, which exhibits a unique
combination of high electrical resistance and good thermal conductivity.
This inert,
non-porous compound is exceptionally pure by virtue of its synthesis
process (high temperature/low pressure chemical vapor deposition).
Products &
Applications PBN Crucibles
For crystal
growth applications, PBN crucibles and boats are used to contain the
melt as it is transformed from a polycrystalline state to a single
crystal. Its ultra-high purity and unique thermal properties make PBN
the ideal crystal growth vessel.
Typical
Properties of Pyrolytic Boron Nitride
|
Apparent Density, gm/cc: |
1.95 – 2.22 |
|
Tensile Strength, MPa (psi) |
40 (6000) |
|
Flexural Strength, MPa (psi) |
80 (12,000) |
Thermal Conductivity, W/m°C “ab” 60, “c” 2
CTE, mm/mm/°C (1000°C) “ab” |
2 x 10-6 |
|
Resistively, ohm-cm |
1015 |
|
Dielectric Strength, D.C. volts/mm |
2 x 105 |
|
Dielectric Constant “ab” 5.2, “c” |
3.4 |
|
Total Metallic Impurities, ppm |
< 10 |
|
Outgassing |
Negligible |
|
Max. Suggested use (°C) |
2500 |
Principal Bulk
Impurities in PBN
|
Impurity |
ppm |
|
Na |
< 2 |
|
Al |
0.4 |
|
Si |
3 |
|
Ca |
3 |
|
Fe |
0.2 |
Measurement
Method SSMS (Spark Source Mass. Spec.) |
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Benefits
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Non-toxic
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High
purity
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Low
density
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Chemically inert protection
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Non-porous
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Outstanding dielectric strength
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Good
thermal conductivity
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Tensile
strength increases with temperature
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Excellent thermal shock resistance
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High
oxidation resistance
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No
auto-doping
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Excellent anisotropy (electrical, mechanical and thermal
The
Pyrolytic process is that of a vapor deposition. It can be considered to
be a crystalline form of Boron Nitride, whereas most BN crucibles are
pressed from powder and then machined, these are created from the BN
vapor and deposited onto a mandrel. (a pyrolytic graphite mandrel for
easy removal.) The benefits are that the PBN crucibles are not porous,
most materials will not stick to the sides because there are no pores
for the materials to reside in. They are more pure than standard BN, and
they can resist any chemical attack better than standard BN, again
because of its density. PBN is the only material that is
resistive to anhydrous HF attack at temps above 1600 C.
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