title: Synthesis and crystal structure of δ-TaON, a metastable polymorph of tantalum oxide nitride.
abstract: δ-TaON was prepared by reaction of gaseous ammonia with an amorphous tantalum oxide precursor. As a representative of the anatase structure (aristotype) it crystallizes in the tetragonal crystal system with lattice parameters a = 391.954(16) pm and c = 1011.32(5) pm. At temperatures between 800 and 850 °C an irreversible phase transformation to baddeleyite-type β-TaON is observed. While quantum-chemical calculations confirm the metastable character of δ-TaON, its transformation to β-TaON is kinetically controlled. The anion distribution of the anatase-type phase was studied theoretically. In agreement with previous studies, it was found that a configuration with maximal N-N distances is most stable. The calculated band edge energies indicate that δ-TaON is a promising photocatalytic material for redox reactions, e.g., water splitting.
authors.affiliation: Institut für Chemie, TU Berlin , Straße des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Lüdtke
authors.forename: Alexander
authors.initials: A
authors.lastname: Schmidt
authors.forename: Caren
authors.initials: C
authors.lastname: Göbel
authors.forename: Anna
authors.initials: A
authors.lastname: Fischer
authors.forename: Nils
authors.initials: N
authors.lastname: Becker
authors.forename: Christoph
authors.initials: C
authors.lastname: Reimann
authors.forename: Thomas
authors.initials: T
authors.lastname: Bredow
authors.forename: Richard
authors.initials: R
authors.lastname: Dronskowski
authors.forename: Martin
authors.initials: M
authors.lastname: Lerch