Samarium(III) fluoride

Samarium(III) fluoride (SmF3) is a slightly hygroscopic solid fluoride. Conditions/substances to avoid are: open flame, moisture, strong acids.

Preparation
Samarium(III) fluoride can be obtained by reacting SmCl3 or Sm2(CO3)3 with 40% hydrofluoric acid:


 * SmCl3 + 3 HF → SmF3↓ + 3 HCl


 * Sm2(CO3)3 + 6 HF → 2 SmF3 + 3 H2O + 3 CO2↑

Samarium(III) fluoride can also be produced by hydrothermal reaction of samarium nitrate and sodium fluroborate at 200 °C.

Chemical
Samarium(III) fluoride reacts with some reducing agents at high temperatures to obtain samarium(II) fluoride:


 * $$\mathsf{ 4 SmF_3 + C \ \xrightarrow{2000^oC}\ 4 SmF_2 + CF_4 }$$
 * $$\mathsf{ 2 SmF_3 + Sm \ \xrightarrow{1800^oC}\ 3 SmF_2 }$$

Physical
At room temperature, samarium(III) fluoride has orthorhombic structure with space group Pnma – β-YF3 type with lattice constants a = 666,9 pm, b = 705,9 pm, c = 440,5 pm. Above 495 °C, it has the rhombohedral LaF3 structure (space group P3cl) – with lattice constants a = 707, c = 724 pm.