Study of the R–(Zr,W)–(O,N) (R = Y, Nd, Sm, Gd, Yb) oxynitride system

The replacement of tantalum by the couple Zr/W within the RTa–O–N systems (R = Y, Nd, Sm, Gd, Yb), enables the preparation of novel oxide and oxynitride phases in the R–Zr–W–O–N system. R2Zr2−xWxO7+x oxides exhibit the fluorite-type (x < 0.9) and scheelite (x ∼ 1) structures. Corresponding oxynitride compositions are of the fluorite-type and show different colors, for example in the case of ytterbium: pale yellow (x = 0.2 or 0.25), green (x = 0.5–0.8) and brown for the tungsten-rich samples (x = 0.9, 1). Photocatalytic activity measurements have been performed to investigate the overall water splitting behavior of these colored phases.