S. Cottenier

The appearance of microcracks in cerium oxide (CeO 2) buffer layers, as used in buffer layer architectures for coated superconductors, indicates the presence of stress between this buffer layer and the substrate. This stress can originate from the differences in thermal expansion or differences in lattice parameters between the CeO 2 buffer layer and the substrate. In this article, we study, by means of ab initio density functional theory calculations, the influence of group IV doping elements on the lattice parameter and bulk modulus of CeO 2. Vegard's law behavior is found for the lattice parameter in systems without oxygen vacancies, and the Shannon crystal radii for the doping elements are retrieved from the lattice expansions. We show that the lattice parameter of the doped CeO 2 can be matched to that of the La 2Zr 2O 7 coated NiW substrate substrate for dopant concentrations of about 5%, and that bulk modulus matching is either not possible or would require extreme doping concentrations. [All rights reserved Elsevier].

We present electronic band structures of transparent oxides calculated using the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. We studied the basic n-type conducting binary oxides In2O3, ZnO, CdO and SnO2 along with the p-type conducting ternary oxides delafossite CuXO2 (X=Al, Ga, In) and spinel ZnX2O4 (X=Co, Rh, Ir). The results are presented for calculated band gaps and effective electron masses. We discuss the improvements in the band gap determination using TB-mBJ compared to the standard generalized gradient approximation (GGA) in density functional theory (DFT) and also compare the electronic band structure with available results from the quasiparticle GW method. It is shown that the calculated band gaps compare well with the experimental and GW results, although the electron effective mass is generally overestimated.