title: Solid-State (29)Si NMR and neutron-diffraction studies of Sr(0.7)K(0.3)SiO(2.85) oxide ion conductors.
abstract: K/Na-doped SrSiO3-based oxide ion conductors were recently reported as promising candidates for low-temperature solid-oxide fuel cells. Sr0.7K0.3SiO2.85, close to the solid-solution limit of Sr1-xKxSiO3-0.5x, was characterized by solid-state (29)Si NMR spectroscopy and neutron powder diffraction (NPD). Differing with the average structure containing the vacancies stabilized within the isolated Si3O9 tetrahedral rings derived from the NPD study, the (29)Si NMR data provides new insight into the local defect structure in Sr0.7K0.3SiO2.85. The Q(1)-linked tetrahedral Si signal in the (29)Si NMR data suggests that the Si3O9 tetrahedral rings in the K-doped SrSiO3 materials were broken, forming Si3O8 chains. The Si3O8 chains can be stabilized by either bonding with the oxygen atoms of the absorbed lattice water molecules, leading to the Q(1)-linked tetrahedral Si, or sharing oxygen atoms with neighboring Si3O9 units, which is consistent with the Q(3)-linked tetrahedral Si signal detected in the (29)Si NMR spectra.
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, P. R. China.
authors.forename: Jungu
authors.initials: J
authors.lastname: Xu
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Fu
authors.forename: Craig M
authors.initials: CM
authors.lastname: Brown
authors.forename: Xiping
authors.initials: X
authors.lastname: Jing
authors.forename: Fuhui
authors.initials: F
authors.lastname: Liao
authors.forename: Fengqi
authors.initials: F
authors.lastname: Lu
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Li
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Kuang
authors.forename: Mingmei
authors.initials: M
authors.lastname: Wu