Thulium phosphate is an inorganic compound of thulium and phosphate with the chemical formula TmPO4. Hydrated forms are also known.
Preparation Hydrated thulium phosphate can be prepared by precipitation from aqueous solutions of thulium(III) chloride and sodium phosphate. A dihydrate has been reported, which can be converted to anhydrous TmPO4 by heating.Kalieva, K.; Stretkova, Z. V.; Babynina, N. A.; Gordienko, L. N.; Votoyarov, M.; Yakimov; Sakavov, I. E.; Mustaev, A. K. "X-ray diffraction studies of praseodymium, neodymium, europium, terbium, dysprosium, erbium, holmium, and terbium orthophosphates". Tr. Kirg. Univ., Ser. Khim. Nauk. 1972. 2: 84–89.
Single crystals of anhydrous TmPO4 can also be grown from a melt containing thulium(III) oxide, ammonium dihydrogen phosphate, lead(II) oxide and phosphorus pentoxide.
Structure and properties Anhydrous thulium phosphate crystallizes in the tetragonal crystal system with the xenotime structure, which is closely related to the zircon structure. It belongs to space group I41/amd (No. 141).
The structure consists of isolated PO4 tetrahedra and eight-coordinate Tm3+ ions. Single-crystal X-ray diffraction and first-principles calculations have been used to study its compression, elastic properties and structural stability. TmPO4 is more resistant to volume compression than to shear deformation, and its elastic anisotropy increases under pressure.
TmPO4 is also a Van Vleck paramagnet. Its magnetic behaviour is dominated by the crystal-field splitting of the Tm3+ 4f levels, and high-field measurements show a field-induced crossover near 30 T at low temperature.
Crystal-field excitations in TmPO4 have also been studied by inelastic neutron scattering.
Reactions Thulium phosphate reacts with sodium fluoride under suitable solid-state conditions to form the fluorophosphate Na3Tm2F3PO4.
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