Fabrication of nanoparticulate porous LaOF films through film growth and thermal decomposition of ion-modified lanthanum diacetate hydroxide

This paper first reports fabrication of macro/nanotextured rare-earth oxyfluoride films. Usage of ion-modified lanthanum diacetate hydroxide (LDAH) as self-templates was successful in producing nanoparticulate lanthanum oxyfluoride (LaOF) films. LDAH template films were deposited on glass substrates through a chemical bath deposition in solutions composed of lanthanum acetate sesquihydrate, methanol, trifluoroacetic acid, and aqueous ammonia. The LDAH films had a unique, nestlike morphology owing to a two-dimensional hexagonal crystal growth. Modification of LDAH with trifluoroacetate ions led to formation of LaOF after pyrolyzing the template films at temperatures of 400-600°C in air. The resultant LaOF films had a nanoparticulate porous microstructure, maintaining the morphology of the original LDAH template films. It was also successful to incorporate Eu³⁺ ions into LaOF through deposition of the LDAH film in a solution containing europium acetate tetrahydrate. The characteristic photoluminescence from Eu³⁺ was observed with an ultraviolet-light excitation at 273 nm, indicating that Eu³⁺ was homogeneously distributed in LaOF host crystals. Thus the ion-modification of LDAH was also demonstrated to be a useful method for preparing nanostructured rare-earth oxyfluoride materials having various cationic compositions.