New titanium hydroxyfluoride Ti_0.75(OH)_1.5F_1.5 as a UV absorber

Alain Demourgues (1) , Nicolas Penin (1) , Etienne Durand (1) , François Weill (1) , Damien Dambournet (1) , Nicolas Viadère (1) , Alain Tressaud (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The microwave-assisted route allows the synthesis of a new Ti hydroxyfluoride adopting a derived form of a ReO₃-type network. Combined techniques such as (i) powder X-ray and neutron diffraction coupled with electron microscopy; (ii) chemical analysis and density measurements; and (iii) FTIR and TGA analyses support the occurrence of Ti vacancies and the stabilization of hydroxyl groups in the vicinity of Ti⁴⁺ cations. A superstructure of the ReO₃ network has been proposed with two Ti sites and two anionic (OH/F) positions. This original compound exhibits UV-shielding properties with an optical band gap around 3.2 eV and could be considered for potential applications as protective UV absorbers.The O(2p)−Ti(3d) charge transfer band, responsible for this absorption, implies the OH groups and the nonbonding character of the 2p valence band. By changing the synthesis conditions which become reducing, Ti³⁺ can be stabilized in this network in an elongated octahedral site as revealed by ESR experiments and UV−visible spectroscopy. This is a second example following the recently prepared Al-based fluoride hydrate with Al vacancies, in which a polarizing cation such as Ti⁴⁺ can accommodate cationic vacancies.

Mots clés: Titanium; UV; Hydroxyfluoride; Inorganic compounds

Domaines: Matériaux

Alain Demourgues, Nicolas Penin, Etienne Durand, François Weill, Damien Dambournet, et al.. New titanium hydroxyfluoride Ti_0.75(OH)_1.5F_1.5 as a UV absorber. Chemistry of Materials, 2009, 21 (7), pp.1275-1283. ⟨10.1021/cm8030297⟩. ⟨hal-00374091⟩