Since the first investigations of perovskite type oxynitrides with the generalised composition ABO 3Àx N x about twenty years ago, these compounds have become of growing interest. The incorporation of nitride ions in the perovskite lattice results in distinct changes in the electronic structure leading to unusual physical properties. In this article we report on new synthesis techniques, different analytical methods, progress in the structural characterisation by comprehensive diffraction techniques and local spectroscopic methods like XAS and NMR as well as state of the art theoretical investigations. Various physical characteristics like electrical and thermal transport parameters and dielectric properties are described. The thermal and chemical stability of oxynitride perovskites are investigated and their applications in different photocatalytic reactions are discussed.

The influence of manganese on the crystallographic phase and the microstructure of BaTi 1؊x Mn x O 3 ceramics (0 < x < 0.05) is investigated. The crystal structure at room temperature changes from tetragonal to hexagonal between x ‫؍‬ 0.005 and 0.017, which causes a drastic change in the microstructure. The Jahn-Teller distortion caused by the Mn Ti 3؉ ions is proposed as the driving force for the phase transition. Annealing of the as-fired samples in both a reducing and oxidizing atmosphere restores the tetragonal phase, which is accompanied by a change in the microstructure based on the percentage of tetragonal phase.

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