Crystal structure and Hirshfeld surface analysis of 2,2 '-(phenylazanediyl)bis(1-phenylethan-1-one)

The whole molecule of the title compound, C22H19NO2, is generated by twofold rotational symmetry. The N atom exhibits a trigonal-planar geometry and is located on the twofold rotation axis. In the crystal, molecules are linked by C-H center dot center dot center dot O contacts with R-2(2)(12) ring motifs, and C-H center dot center dot center dot pi interactions, resulting in ribbons along the c-axis direction. van der Waals interactions between these ribbons consolidate the molecular packing. Hirshfeld surface analysis indicates that the greatest contributions to the crystal packing are from H center dot center dot center dot H (45.5%), C center dot center dot center dot H/H center dot center dot center dot C (38.2%) and O center dot center dot center dot H/H center dot center dot center dot O (16.0%) interactions

The role of Tb-doping on the structural and functional properties of Bi4-xTbxTi3O12 ferroelectric phases with the Aurivillius type structure

Synthesis, crystal structure, dielectric, and magnetic properties of the Aurivillius phase Bi4-xTbxTi3O12 (x = 0.0, 0.4, 0.6, 0.8) are reported. The samples were synthesized using standard solid state reaction technique. The thermal stability of the obtained solid solutions was investigated. For x ae<currency> 0.8, the samples crystallized in an orthorhombic symmetry. All the samples showed finite second harmonic generation response indicating a non-centrosymmetric structure. The structural data could be refined using the polar orthorhombic space group B2cb. The orthorhombicity decreases with an increase in the Tb3+ concentration. The orthorhombic distortions in these compositions are related to the Bi3+-based perovskite sublattice. Our results indicate that the non-lone pair Tb3+ cations preferentially occupy the perovskite sublattice initially, but with an increase in the doping concentration they can partially substitute the Bi3+ ions in the fluorite block. Temperature dependent dielectric measurements revealed a decrease in the ferroelectric Curie temperature T-C with an increase in x from T-C = 904 K (for x = 0) to 877 K (for x = 0.4). Further increase in x led to a cross-over to a relaxor-type behavior. Magnetic measurements showed that the samples are paramagnetic down to 5 K

Composition dependence of the multifunctional properties of Nd-doped Bi4Ti3O12 ceramics

Sample preparation, evolution of the crystal structure with Nd content at room temperature, as well as dielectric and magnetic properties of polycrystalline Bi4-xNdxTi3O12 solid solutions (x = 0.0, 0.5, 1.0, 1.5, and 2.0) are reported. These solid solutions were structurally characterized by X-ray powder diffraction using Rietveld refinements. For x <= 1.0, the samples crystallize in an orthorhombic symmetry. The structural data could be refined using the polar orthorhombic space group B2cb. The orthorhombicity decreases with increasing Nd3+ concentration, and a paraelectric tetragonal structure (space group I4/mmm) is stabilized for x > 1. The ferroelectric Curie temperature was found to monotonously decrease with increasing Nd concentration. A polar-to-nonpolar phase transition takes place near x = 1, reflecting the existence of a morphotropic phase boundary between 1.0 < x < 1.5 at room temperature. All samples were found to be paramagnetic down to 5 K, however, the presence of significant antiferromagnetic interaction is inferred from Curie-Weiss analyses of the temperature dependence of the magnetic susceptibility of the doped samples. The effect of Nd3+ substitution on structure-property relationship is discussed and compared to that of other lanthanide cations