Crystal Structure and Properties of Ba₁₁FeTi₂₇O_66.5.

Abstract

Structure Structure D 2000Crystal Structure and Properties of Ba 11 FeTi 27 O 66.5 . -The title compound is prepared by solid state reaction of BaCO 3 , Fe 2 O 3 , and TiO 2 at 1260°C and its structure is determined by single crystal XRD. Ba11FeTi27O66.5 crystallizes in the monoclinic space group C2/m with Z = 2. The compound exhibits a 10-layer structure built from close-packed [O,(Ba,O)] layers with a stacking sequence (cchhc)2. The octahedral sites are occupied by a mixture of Fe 3+ and Ti 4+ , with some preferential ordering suggested by analysis of bond valence sums. The structure features vertex-, edge-, and face-sharing of the Ti(Fe)O6 octahedra. Magnetic and dielectric properties of the compound are reported. -(VANDERAH*, T. A.; SIEGRIST, T.; ROTH, R. S.; RAMIREZ, A. P.; GEYER, R. G.; Eur.

Structure Property Relationship in BaTiO3–Na0.5Bi0.5TiO3–Nb2O5–NiO X8R System

“…However, the relative concentration of this phase decreases with increasing Ni content, as observed from the decreasing diffraction peak intensity at 30.7°. Because the present BT‐NBT‐Nb‐Ni system has similar synthesis condition as Ba 11 (Fe,Ti) 28 O 66+ x ceramic (at 1260°C), it is assumed that NiO first reacts with excess BaO and TiO 2 during sintering, forming the Ba 11 (Ni,Ti) 28 O 66+ x phase. As the Ni concentration increases, the excess BaO and TiO 2 are run out.…”

“…For the A 11 B 28 O 66+ x ‐type phase, the B site could be occupied with a small amount (<10 at.%) of a trivalent metal, which determines the value of x (Ref. ). Given that the effective ionic radii of the Ni 3+ impurity cation [i.e., 0.56 Å (low‐spin) and 0.60 Å (high‐spin)] are smaller than Ti 4+ (0.605 Å), the main peak position of A 11 B 28 O 66+ x ‐type phase (30.7°) locates at higher degree than the reported main peak of Ba 11 Ti 28 O 66+ x (29.3°) .…”

“…). Given that the effective ionic radii of the Ni 3+ impurity cation [i.e., 0.56 Å (low‐spin) and 0.60 Å (high‐spin)] are smaller than Ti 4+ (0.605 Å), the main peak position of A 11 B 28 O 66+ x ‐type phase (30.7°) locates at higher degree than the reported main peak of Ba 11 Ti 28 O 66+ x (29.3°) . Thus, we speculate the transition metals (Ni 3+ ) occupy octahedral interstices, that is, [(Ti 4+ /Ni 3+ )O 6 ] octahedra, to form a Ba 11 (Ni,Ti) 28 O 66+ x phase.…”