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Potassium Bromide KBr
Potassium Bromide is one of the most useful materials for general purpose spectroscopic windows and applications where sensitivity to moisture is unimportant. Potassium Bromide is the most commonly used beamsplitter material for IR spectrophotometers.
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| Transmission Range | 0.23 to 25 μm |
| Refractive Index | 1.527 at 10 μm (1) |
| Reflection Loss | 8.3% at 10 μm (2 surfaces) |
| Absorption Coefficient | 3 x 10-6 @ 1064 nm; 14 x 10-6 cm-1 @ 10.6 μm (7) |
| Reststrahlen Peak | 77.6 μm |
| dn/dT | -40.8 x 10-6/°C (1) |
| dn/dμ | 4.2 μm |
| Density | 2.753 g/cc |
| Melting Point | 730°C |
| Thermal Conductivity | 4.816 W m-1 K-1 @ 319 K (3) |
| Thermal Expansion | 43 x 10-6/°C @ 300 K (4) |
| Hardness | Knoop 7 in with 200g indenter (4) |
| Specific Heat Capacity | 435 J Kg-1 K-1 |
| Dielectric Constant | 4.9 at 1 MHz (6) |
| Young's Modulus (E) | 26.8 GPa (4) |
| Shear Modulus (G) | 5.08 GPa (4) |
| Bulk Modulus (K) | 15.03 GPa (4) |
| Elastic Coefficients | C11 = 34.5; C12 = 5.4; C44 = 5.08 (5) |
| Apparent Elastic Limit | 3.3 MPa (475 psi) (4) |
| Poisson Ratio | 0.203 |
| Solubility | 53.48 g/100 g water at 273 K |
| Molecular Weight | 119.01 |
| Class/Structure | Cubic FCC, NaCl, Fm3m, (100) cleavage |
| μm | No | μm | No | μm | No |
|---|---|---|---|---|---|
| 0.405 | 1.5898 | 1.014 | 1.5441 | 14.29 | 1.5150 |
| 0.436 | 1.5815 | 2.440 | 1.5373 | 17.40 | 1.5039 |
| 0.486 | 1.5718 | 3.419 | 1.5361 | 19.91 | 1.4929 |
| 0.508 | 1.5684 | 4.258 | 1.5352 | 23.86 | 1.4714 |
| 0.546 | 1.5639 | 6.238 | 1.6329 | 25.14 | 1.4632 |
| 0.587 | 1.5600 | 8.662 | 1.5290 | 28.00 | 1.4423 |
| 0.643 | 1.5559 | 9.724 | 1.5270 | 30.00 | 1.4253 |
| 0.707 | 1.5524 | 11.04 | 1.5240 |
Potassium Bromide is produced in large ingots by the Kyropoulos growth method. Potassium Bromide cleaves easily. With care Potassium Bromide can be polished to a high standard under humidity controlled conditions.
REFERENCES:
(1) Stephens et. al.; J.Opt. Soc. Am. V43, p111, 1953
(2) Kohler; Z. Physik. Volk 78, p375. 1932
(3) Ballard, McCarthy & Davis; Rev. Sci. Insts, V21, p905, 1970
(4) Combes, et.al.; J.Opt. Soc. Am. V41, p215, 1951.
(5) Huntingdon; Phys.Rev. V72, p321, 1947
(6) Hipple; Dielectric Materials & Applications. Wiley
(7) H.H.Li, Absorption Coefficients, Int.J.Therm, V1, No. I, 1980