Chemical Substitution-Induced and Competitive Formation of 6H and 3C Perovskite Structures in Ba_3–xSr_xZnSb₂O₉: The Coexistence of Two Perovskites in 0.3 ≤ x ≤ 1.0

Abstract

6H and 3C perovskites are important prototype structures in materials science. We systemically studied the structural evolution induced by the Sr-to-Ba substitution to the parent 6H perovskite BaZnSbO. The 6H perovskite is only stable in the narrow range of x ≤ 0.2, which attributes to the impressibility of [SbO]. The preference of 90° Sb-O-Sb connection and the strong Sb-Sb electrostatic repulsion in [SbO] are competitive factors to stabilize or destabilize the 6H structure when chemical pressure was introduced by Sr incorporation. Therefore, in the following, a wide two-phase region containing 1:2 ordered 6H-BaSrZnSbO and rock-salt ordered 3C-BaSrZnSbO was observed (0.3 ≤ x ≤ 1.0). In the final, the successive symmetry descending was established from cubic (Fm3̅m, 1.3 ≤ x ≤ 1.8) to tetragonal (I4/m, 2.0 ≤ x ≤ 2.4), and finally to monoclinic (I2/m, 2.6 ≤ x ≤ 3.0). Here we proved that the electronic configurations of B-site cations, with either empty, partially, or fully filled d-shell, would also affect the structure stabilization, through the orientation preference of the B-O covalent bonding. Our investigation gives a deeper understanding of the factors to the competitive formation of perovskite structures, facilitating the fine manipulation on their physical properties.

Stable 6H Organic–Inorganic Hybrid Lead Perovskite and Competitive Formation of 6H and 3C Perovskite Structure with Mixed A Cations

“…In contrast, the MA-rich 3C solid solution follows Vegard’s law and shows a linear increase in unit cell volume with increasing average A cation size. Similar behavior has been observed in the isostructural 6H-3C perovskite oxide solid solution Ba 3– x Sr x ZnSb 2 O 9 …”

Site-selective doping effect, phase separation, and structure evolution in 1:1:1 triple-cation B-site ordered perovskites Ca4−xSrxGaNbO8

“…the two-phase region observed in Ba 3− x Sr x ZnSb 2 O 9 (0.3 ≤ x ≤ 1.0). 28 Such a difference is attribute to the subtle distinction in crystal structures between Ca 4 -type and Sr 4 -type structures, which will be discussed later.…”

Equivalent chemical substitution in double–double perovskite-type ALaLiTeO6:Mn4+ (A = Ba2+, Sr2+, Ca2+) phosphors enabling wide range crystal field strength regulation and efficient far-red emission

“…These changes in lattice parameters are usually originated from the reorientations of octahedral tilting, which has been documented for many B-site-ordered double perovskites. 51 Herein, it is specifically attributed to the change of the tilting system from a − a − c 0 (I2/m) to a − a − c + (P2 1 /n) (see Fig. 3).…”