The crystalline substance known as silver bromide is soft, yellowish, and insoluble in water. Many IR material standards state that the formation of silver bromider crystals is a recent development. In comparison to silver chloride, silver bromide parameters have not been investigated as thoroughly. Silver bromide is a useful material for deep IR applications. Silver bromide substance is a versatile material that Alfa Chemistry may employ to create optical components in almost any shape or size as requested by the customer. Contact us if you require assistance.
Advantages and Uses of Silver Bromide Materials
Silver bromide is a non-glass, inorganic optical material with a fairly high density in non-glass optical ceramics. Measurements of reflectance in the energy range of 3~16 eV have been used to establish the optical characteristics of silver bromide at ambient temperature. Silver bromide is frequently employed in optical applications because of its broad transmission range (0.45 to 35 µm) and extremely high refractive index of 2.31 (thickness of 0.5 µm). Silver bromide is sensitive to moisture. This soft crystal deforms under heat and pressure and can be forged in polished dies to create infrared windows and lenses. In addition, it has a fairly low melting temperature and moderately low thermal conductivity. When exposed to sunlight, silver bromide is less likely to tarnish than silver chloride, and it is also ductile.
Fig 1. The absorbance of AgBr crystals at increasing times after light exposure (measured by Diffuse Reflectance Spectroscopy. The Kubelka-Munk factor is proportional to the absorbance): (a) optical absorption spectra; and (b) kinetics of the absorbance increase at the maximum. (Belloni J, et al. 2003)
Properties of Silver Bromide Materials
| Density | 6.473 g/cc |
| Molecular Weight | 187.78 |
| Solubility | 12x10-6g/100g water at 20°C |
| Class/Structure | Cubic FCC, NaCl, Fm3m, No cleavage, cold flows |
| Melting Point | 432 °C |
| Hardness | Knoop 7 |
| Refractive Index | 2.167 at 10 μm |
| Transmission Range | 0.45 to 35 μm |
| Reflection Loss | 23.9% at 10 μm |
| Reststrahlen Peak | 112.7 μm |
| Apparent Elastic Limit | 30.3 MPa (4400psi) |
| Youngs Modulus (E) | 31.97 GPa |
| Bulk Modulus (K) | 44.03 GPa |
| Thermal Expansion | 30 x 10-6/°C at 273 K |
| Thermal Conductivity | 1.21 W/m/K at 273 K |
| Dielectric Constant | 13.1 at 1MHz |
| Specific Heat Capacity | 292 J Kg-1 K-1 |
| Elastic Coefficients | C11=56.3 C12=32.3 C44=7.25 |
About refractive index parameters.
"No" means ordinary light.
| µm | No | µm | No | µm | No |
|---|---|---|---|---|---|
| 0.391 | 2.416 | 0.477 | 2.33 | 0.496 | 2.313 |
| 0.55 | 2.27 | 0.6 | 2.25 | 0.65 | 2.24 |
| 0.781 | 2.205 | 9.926 | 2.167 | 12.66 | 2.162 |
Reference
- Belloni J, et al. (2003). "Photography: Enhancing Sensitivity by Silver-Halide Crystal Doping." Radiation Physics and Chemistry. 67(3): 291-296.