Extended X-ray absorption fine structure analysis of (Ca,Nd)(Ti,Al)O3 perovskite ceramics used in cellular base stations

The local structural environments for Ca, Nd and Ti atoms in Ca0.7Nd0.3Ti0.7Al0.3O3 ceramics were studied at 298 K using extended X-ray absorption fine structure (EXAFS) analysis. The theoretical EXAFS spectra were in excellent agreement with experimental EXAFS data. There was very good agreement between EXAFS-derived distances and X-ray data for Ti (all three shells), but for Ca and Nd the EXAFS distances for the first co-ordination shell (Ca–O and Nd–O) were significantly less than values obtained from X-ray analysis and Shannon’s ionic radii; also, co-ordination numbers were inconsistent with X-ray results for Ca and Nd. The similarity in the data for Ca and Nd confirms that the cations sit in a shared site, where there is large disorder in (Ca/Nd)–O distances. Bond valence sums for the Ti site were abnormally high, indicating compression of the site, possibly as a result of compositionally induced strain.