Chemical-substitution-induced successive symmetry descent and structure–property correlation for “114” oxides CaBa1−xSrxZn2Al2O7

Abstract

The crystal structures, photoluminescence properties, and transport properties of a series of new “114” oxides CaBa_1−xSr_xZn₂Al₂O₇ (x = 0–1) were investigated in detail. Careful Rietveld refinements performed on solid solution samples revealed that the structural symmetry of CaBa_1−xSr_xZn₂Al₂O₇ evolves from hexagonal P6₃mc (x < 0.2) to trigonal P31c (0.2 ≤ x ≤ 0.6) and then to orthorhombic Pna2₁ (x > 0.6) with an increase of the Sr²⁺-content, which is cooperative with the rotation of T1O₄ tetrahedra around the c-axis. Eu³⁺ was used as a local structural probe to gain an insight into the structure, which further corroborated the correctness of the observed structural symmetry descending sequence in CaBa_1−xSr_xZn₂Al₂O₇. More importantly, the reduction of structural symmetry is also associated with a tendency from layered ordering to complete charge ordering transition for Zn²⁺/Al³⁺ cations, which was revealed to have a significant influence on the transport properties. These findings are expected to offer a route to manipulate the physical properties of “114” oxides containing magnetic cations.