Cation Ordering Types and Dielectric Properties in the Complex Perovskite Ca(Ca1/3Nb2/3)O3

Complex Polymorphic Behavior and Dielectric Properties of Perovskite-Related Sr(Sr1/3Nb2/3)O3

“…The shoulders become more pronounced in the Raman spectrum of the 9003C-annealed specimen, which suggests that they are related to the metastable superstructures. Previously, development of similar shoulders was observed to accompany formation of the metastable Ca Nb O polymorph with k"1/4[111]* ordering on the mixed B1 sites of the 1:1 ordered B-cation array (9). This correlation is consistent with an additional ordering on the B1 sites proposed by the structural analyses of the metastable phases in the 9003C-annealed Sr Nb O .…”

“…Additionally, non-stoichiometric A(B >V B \V )O \B perovskites exhibit ionic conductivity (4) and can also absorb signi"cant proton concentrations to become proton conductors (5,6). The typical crystal}chemical e!ects observed in these systems include B-cation ordering (7) and/or structural distortion approximated by rotation of nearly rigid [BO ] octahedra (8,9); both e!ects are known to substantially in#uence dielectric and electrical properties (8,10). For the stoichiometry A(B B )O , two common B-site ordering types have been reported with the ordering vectors k"1/3[111]* (1:2 type) and k"1/2[111]* (1:1 or NaCl type), respectively (7), where subscript &c' refers to the ideal cubic &4 A s perovskite unit cell.…”

“…Recently, a third metastable polymorph with partial ordering on the &&random'' sites of the 1:1 ordered array, described by a vector k"1/4[111]* , was reported for the compound Ca(Ca Nb )O (9,10). Following studies of polymorphism in Ca(Ca Nb )O , our attention focused on analogs with cations larger than Ca (i.e., Sr or Ba) possibly occupying both A-and B-sites.…”

Influence of the calcium excess in the structural and spectroscopic properties of the complex perovskite Ba3CaNb2O9

“…4 to indicate the relationship between Raman intensity and the stoichiometry. The peak at 700 cm −1 seems to have a direct relation with the oxygen vacancies; this peak is absent in the work of Levin, where no extrinsic oxygen vacancies exist [13]. BCN18 has a peak intensity slightly below the trend of the series indicating some oxygen vacancies are filled with OH species.…”

Phase Equilibria and Dielectric Behavior in the CaO:Al2O3:Nb2O5 System

“…The CaO}Al O system has been well studied owing to its importance in structural ceramic materials (15) (31,32). This compound exhibits four structures with di!erent Ca and Nb ordering on the B-cation sites.…”