title: KNi(0.93)Fe(II)(0.07)Fe(III)(PO4)2: a new type of structure for a compound of composition M(I)M(II)M(III)(PO4)2.
abstract: The solid solution KNi(0.93)Fe(II)(0.07)Fe(III)(PO4)2 {potassium [nickel(II)/iron(II)] iron(III) bis(orthophosphate)} has been prepared by the flux method. The compound shows a new type of structure for a phosphate with the general composition M(I)M(II)M(III)(PO4)2. The framework is formed by [(Ni/Fe)O6] polyhedra [Fe site occupancy = 0.069 (14)] linked via shared oxygen vertices forming a cis-like parallel chain stretching along a and [FeO5] polyhedra (located on alternate sides of the chains) connected via two types of PO4 groups into a three-dimensional structure. The K atoms are disordered between two sites, denoted K1A and K1B, with occupancies of 0.930 (9) and 0.070 (9), respectively, and reside inside channels along the a axis. Calculations of the Voronoi-Dirichlet polyhedra of the K atoms give a coordination scheme for K1A of [9 + 3] and for K1B of [10 + 2]. The most remarkable feature of the structure is the splitting of the K-atom site and the population of the K1A and K1B positions due to substitution of Ni by Fe in the (Ni/Fe) position.
authors: Department of Inorganic Chemistry, Taras Shevchenko National University, 64/13 Volodymyrska Str., 01601 Kyiv, Ukraine.
authors: Nataliya Yu
authors: NY
authors: Strutynska
authors: Department of Inorganic Chemistry, Taras Shevchenko National University, 64/13 Volodymyrska Str., 01601 Kyiv, Ukraine.
authors: Igor V
authors: IV
authors: Zatovsky
authors: STC `Institute for Single Crystals', NAS of Ukraine, 60 Lenin Ave., 61001 Kharkiv, Ukraine.
authors: Vyacheslav N
authors: VN
authors: Baumer
authors: Department of Inorganic Chemistry, Taras Shevchenko National University, 64/13 Volodymyrska Str., 01601 Kyiv, Ukraine.
authors: Ivan V
authors: IV
authors: Ogorodnyk
authors: Department of Inorganic Chemistry, Taras Shevchenko National University, 64/13 Volodymyrska Str., 01601 Kyiv, Ukraine.
authors: Nikolay S
authors: NS
authors: Slobodyanik
keywords: crystal structure; potassium nickel iron orthophosphate; solid solution