Synthesis of [(H3O)Tm3F10] · nH2O, ErF3, and TmF3 powders and their physicochemical properties

Abstract

Reaction of Er₂S₃ powder with aqueous HF solution (49%) followed by drying of the resultant precipitate at 25–95°C has afforded X-ray amorphous phase preferably as ErF₃ · 0.87H₂O hydrate. The resultant phase have been shown to undergo thermal dissociation at 50–165°C (ΔH = 97.8 J/g, Δm = 5.5 wt %), Δm is 1 wt % in temperature range 165–270°C. Exothermal effect at 236–270°C (ΔH =–64.3 J/g) has correlated with formation of polycrystalline compound ErF₃: space group Pnma, a = 0.634(8) nm, b = 0.684(2) nm, c = 0.438(2) nm. The size of particles of ErF₃ phase formed at 170°C calculated by the Selyakov–Scherrer formula has been found to be 45 × 60 nm. The reaction of Tm₂S₃ with HF solution at 25°C has led to a phase of composition [(H₃O)Tm₃F₁₀] · 1.7H₂O: space group Fd3-m, a = 1.5389(5) nm whose particles are regular octahedra in shape and 4–8 μm in size. Upon heating of the prepared compound to 150°C (ΔH = 51.1 J/g, Δm = 4.2 wt %), water molecules go to gas phase, while crystal structure of the phase retains: a = 1.5353(3) nm. Three-quarter of water molecules nave been lost in temperature range 150–225°C (ΔH = 23.4 J/g, Δm = 3.8 wt %). Exothermal effect at 225–270°C (ΔH =–18.8 J/g) has been accompanied by formation of polycrystalline structure of compound TmF₃: space group Pnma, a = 0.627(8) nm, b = 0.681(3) nm, c = 0.440(9) nm. Particles of compound TmF₃ have been found to be 110–250 nm in size.