Hydrothermal Synthesis and Crystal Structure of a Novel Bismuth Oxide: (K(0.2)Sr(0.8))(Na(0.01)Ca(0.25)Bi(0.74))O(3)

[Image: see text] A novel distorted perovskite-type (K(0.2)Sr(0.8))(Na(0.01)Ca(0.25)Bi(0.74))O(3) was prepared by a hydrothermal method using the starting materials NaBiO(3)·nH(2)O, Sr(OH)(2)·8H(2)O, Ca(OH)(2), and KOH. Single-crystal X-ray diffraction of the novel compound revealed a GdFeO(3)-related structure belonging to the monoclinic system of the space group Cc with the following cell parameters: a = 11.8927 (17) Å, b = 11.8962 (15) Å, c = 8.4002 (10) Å, and β = 90.116 (9)°. The final R-factors were obtained as R(1) = 0.0354 and wR(2) = 0.0880 (using all the data). K(+) and Sr(2+) ions were distributed at four types of A-sites. On the other hand, four Bi(5+)-sites (Bi1, Bi2, Bi3, and Bi4) were occupied by four Ca(2+) ions (Ca1, Ca2, Ca3, and Ca4), and the first three B-sites were occupied predominantly by Bi(5+) with Na(+) ions. The forth B-site was occupied predominantly by the Ca(2+) ion with Bi(5+) ions. Two types of B-sites, thus forming tilted distorted (Na/Ca/Bi)O(6) and (Bi/Ca)O(6) octahedra, have an ordering of 3:1 represented as (K/Sr)(4)(Na/Ca/Bi)(3)(Bi/Ca)O(12). The distorted (Na/Ca/Bi)O(6) and (Ca/Bi)O(6) octahedra formed a perovskite-type network by corner sharing with features closely matching those of a GdFeO(3)-type structure. The novel compound is the first example of a perovskite-type bismuth oxide containing only Bi(5+) in a system without a Ba atom and has a unique ordering (3:1) of the B site. The compound showed photocatalytic activity for phenol degradation under visible light irradiation.