Microstructural Characteristics of Strontium Magnesium Niobate

Abstract

Microstructural studies were conducted on the domain boundaries in Sr(Mg 1/3 Nb 2/3 )O 3 (SMN) complex perovskite compound using X-ray diffractometry and transmission electron microscopy. Both the 1:2 chemical ordering of B-site cations and the tilting of oxygen octahedra were involved in SMN. SMN had a 1:2 ordered monoclinic unit cell, which was distorted by the antiphase tilting of oxygen octahedra. Two types of domain boundaries were found: the antiphase boundaries (APBs), which are not confined crystallographically, and the ferroelastic domain boundaries, which were parallel to the crystallographic planes. SMN had the superlattice reflections of type ؎ 1 ⁄6[111] and ؎ 1 ⁄2[111] in the electron diffraction patterns, which cannot be indexed in terms of the 1:2 ordered trigonal phase with only a hexagonal unit cell. The presence of the ferroelastic domains that contained both the 1:2 ordered and the antiphase tilting had been verified by a high-resolution transmission electron microscopy lattice image. The structure of SMN was well explained by a model proposed by other researchers. The formation of the 1:2 ordered domains preceded the ferroelastic domains. Normally, the growth of the ferroelastic domain is not affected by APBs, but it is interrupted by them when the driving force for growth is insufficient, resulting in the stoppage of the domains at APBs.

Raman signatures of monoclinic distortion in (Ba1−xSrx)3CaNb2O9 complex perovskites

“…The atomic substitution for smaller ions at the A site leads to the crystal symmetry lowering due to the A─O bond decrement along with the octahedral tilting, in which the BO 6 octahedra are tilted in order to preserve the connectivity of their corners . Such a behavior increases the number of the diffraction peaks as a result of the symmetry lowering process . Fig.…”

“…proposed that the antiphase tilting of both MgO 6 and TaO 6 octahedra changed the space group of the (Ba 1− x Sr x ) 3 MgTa 2 O 9 compounds from trigonal (D 3d 3 ) to monoclinic (C 2h 6 ; A 2/ n or C 2/ c ; #15) . Another evidence of this phase transition comes from the (2 0 2) h peak splitting into two counterparts indexed as (2–4 2) and (2 4 2) reflections from the monoclinic phase . This behavior was not noticed here for the (2 0 2) h peak [Fig.…”

“…It means that the BCN–SCN may experience a phase transition as the Sr 2+ substitution increases. Hence, one can expect a distorted 1:2 structure for SCN rather than the undistorted D 3d cell for BCN . To investigate those structural changes in more detail, Raman scattering measurements were collected in all samples of the BCN–SCN solid solution at room temperature, as discussed next.…”

Vibrational modes and structural characteristics of (Ba0.3Sr0.7)[(ZnxMg1−x)1/3Nb2/3]O3 solid solutions

“…Based on the nomenclature adopted by Lee et al 16 and Nagai et al 19 for a hexagonal cell of a Ba(Sr 1/3 Ta 2/3 )O 3 -type structure, a careful analysis should be done in 2q regions of the XRD patterns: the first region at 30-40 • 2q and the second one at 44-46 • 2q. Fig.…”

Lattice dynamics and phonon characteristics of complex perovskite microwave ceramics

“…Nagai et al [37] developed new models to explore the 1:2 ordered structures and the oxygen octahedral distortion of ‐type MWDCs, and thought the structural change of BSMT ceramics is related to the strontium substitution. Subsequently, the BSMN ceramics are researched and two regions: the 1:2 ordered trigonal structures and the 1:2 chemical ordered structures are identified by Lee et al [86], without and with the tilting of the oxygen octahedron, respectively.…”