Syntheses And Characterization Of New Iron,Cobalt,Nickel Phosphates

Transition-metal Phosphate is a branch of inorganic framework material.Preparation of new transition-metal phosphates is always an active field due to their rich structural chemistry as well as their excellent performance on magnetic,electrical,optic field.Transition-metal phosphates have widely applications in catalysis,lithium ion batteries,and fertilizers.The introduction of fluorine in the metal phosphate framework structures can effectively replace the oxygen atom positions and the hydroxide group sites in both metal octahedra and phosphate tetrahedra as a bridging linker or a tailed terminal,exerting significant effects on the structural and compositional chemistry of phosphates.But because of the limitation of synthesis methods,the current number of transition-metal fluorophosphates is less.This situation lasted till the introduction of novel synthesis route of "high fluorine and low water" by the Weller’s group.Weller’s group synthesized dozens of transition-metal fluorophosphates through this method without deep research on their magnetic or electrical properties.This paper using improved "high fluorine and low water" route synthesized 5 fluorophosphates or chlorine-inclusion phosphates.We use phosphoric acid as solvent and metal fluoride as source of fluorine,without adding any additional water to the reagent.The results of this paper are as follows:(1)A new nickel fluorophosphate KNi3｛PO3[F0.62(OH)0.38]｝2(H2PO4)F2 had been synthesized using improved "high fluorine and low water" route.Structural characterizations show that it adopts a 3D framework structure with 2D layers of Ni octahedra in a stair-case Kagome lattice.The Ni2 octahedron at the inversion center shares two trans-faces with Nil octahedra to form a Ni1-Ni2-Nil linear trimer(Ni3OsF6)as the basic structural unit.Ni-trimers are linked between themselves by sharing F-cormers and to[PO3(F,OH)]tetrahedral groups by sharing O-corners to form 2D stair-case Kagome lattice layers,which are parallel to the(100)plane and stacked along a-axis.Successive Kagome layers are combined together by[PO2(OH)2]tetrahedral groups and interstice cations K+.Magnetic measurements reveal that KNi3[PO3(F,OH)]2[PO2(OH)2]F2 exhibits a canted antiferromagnetic ordering with a ferromagnetic component at low temperatures.(2)Two new fluorophosphates K3Fe(PO3F)2F2 and BaNiPO4F had been synthesized.K3Fe(PO3F)2F2 was synthesized using phosphoric acid as solvent,hydrofluoric acid and KF as source of fluorine,without adding any additional water.K3Fe(PO3F)2F2 was found to contain 1-D structural u.nit,the 1-D chain is constructed of four membered rings formed from two Fe octahedra and two phosphate tetrahedral,polyhedra are linked through oxygen.BaNiPO4F was synthesized using improved "high fluorine and low water" route,we using high concentration KOH solvent control the pH value and water content of the reagent.BaNiPO4F is 3-D framework structure.The Ni octahedra formed 1-D chain through sharing two peak oxygen atoms.Then the 1-D chains are combined together by[PO4]tetrahedral groups.IR and TG test confirm the component and structure of two compounds.(3)Two new chlorine-inclusion phosphates K6Ni2(HPO4)2(P2O7)Cla·4.36H2O and K6Co2(HPO4)2(P2O7)Cl2-4.36H2O had been synthesized using improved "high fluorine and low water" route,we using high concentration KOH solvent control the pH value and water content of the reagent.These two isostructure compound are in cubic system,with 3-D pore structure.