Crystal structures of gadolinium- and yttrium-doped barium cerate

Abstract

The crystal structures of two doped, oxide ion and protonic conducting perovskites, BaCe_0.9M_0.1O_2.95 with M = Gd or Y, have been refined from room-temperature neutron powder diffraction data. Both compounds are orthorhombic, space group Pmcn, Z= 4, with lattice constants a= 8.7705(4)Å, b= 6.2233(3)Å, c= 6.2393(3)Å for BaCe_0.9Y_0.1O_2.95 and a = 8.7728(16)Å, b= 6.2219(12)Å, c= 6.2443(14)Å for BaCe_0.9Gd_0.1O_2.95. The lattice constants and fractional coordinates of both compounds are shifted only slightly from the undoped compound indicating the good lattice match of Y³⁺/Gd³⁺ for Ce⁴⁺. For Y-doping, the extrinsic anion vacancy has been found to lie on only one of the two crystallographically distinct oxygen sites but the extreme absorption cross-section of Gd precluded refinement of the oxygen site occupancies in BaCe_0.9Gd_0.1O_2.95.