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Lanthanum Fluoride LaF3:Eu3+
Lanthanum Fluoride is not often used as an optical material. Lanthanum Fluoride is usually doped with Europium at a nominal level of 0.3% mole. In this form, the usual application is as the active element in an ion-selective electrode for the detection and measurement of Fluoride ions in solution.
| Transmission Range | 0.2 to 11 μm |
| Refractive Index | No = 1.506 at 0.55 μm |
| Reflection Loss | n/a |
| Absorption Coefficient | n/a |
| Reststrahlen Peak | n/a |
| dn/dT | n/a |
| dn/dμ = 0 | n/a |
| Density | 5.94 g/cc |
| Melting Point | 1493°C (1) |
| Thermal Conductivity | 5.1 W m-1 K-1 @ 300 K |
| Thermal Expansion | 11x10-6 /K (para) 15.8x10-6 /K (perp) at 298K (2) |
| Hardness | Moh 4.5 |
| Specific Heat Capacity | 506 J Kg-1 K-1 |
| Dielectric Constant | 14 (3) |
| Youngs Modulus (E) | n/a |
| Shear Modulus (G) | n/a |
| Bulk Modulus (K) | n/a |
| Elastic Coefficients | n/a |
| Apparent Elastic Limit | n/a |
| Poisson Ratio | n/a |
| Solubility | Insoluble in water |
| Molecular Weight | 195.9 |
| Class/Structure | Trigonal (hex), P63/mcm (2), no cleavage |
| μm | No | Ne |
|---|---|---|
| 0.254 | 1.656 | 1.649 |
| 0.405 | 1.618 | 1.612 |
| 0.436 | 1.617 | 1.609 |
| 0.547 | 1.606 | 1.602 |
Lanthanum Fluoride is grown as small ingots of about 10mm diameter as it is difficult to anneal. Doped with Europium, it is a pale yellow colour.
REFERENCES:
(1) Jones and Shand, J.Crys.Growth. 2 (1968) p3611
(2) Sher, Solomon, Lee, and Meuller. Phys.Rev. 144, p593 (1966)
(3) Electronic Processes in Ionic Crystals (OU Press, NY, 1940) p.41