La-Driven Morphotrophic Phase Boundary in the Bi(Zn_1/2Ti_1/2)O₃–La(Zn_1/2Ti_1/2)O₃–PbTiO₃ Solid Solution

Abstract

We explore the Bi(Zn1/2Ti1/2)O3–La(Zn1/2Ti1/2)O3–PbTiO3 pseudoternary phase diagram using density functional theory and a solid solution model. We find a region of stability against phase segregation that contains a morphotropic phase boundary. On the basis of the results, we identify a ferroelectrically active composition-dependent region that is likely to show strong electro-mechanical response. Furthermore, we find that La replacement for Bi not only lowers the polarization as might be expected, but also shifts the balance from tetragonality toward rhombohedral distortions. This may be of general use in modifying phase diagrams of A-site driven perovskite ferroelectric solid solutions to generate new morphotropic phase boundary systems.

Na1/2Bi1/2VO3 and K1/2Bi1/2VO3: New Lead-Free Tetragonal Perovskites with Moderate c/a Ratios

“…PbTiO 3 -type bismuth-based perovskites, including BiCoO 3 ( c / a = 1.27; P S = 126 μC/cm 2 by the point charge model), , Bi 2 ZnTiO 6 ( c / a = 1.21; P S = 103 μC/cm 2 by the point charge model), and Bi 2 ZnVO 6 ( c / a = 1.26; P S = 126 μC/cm 2 by the point charge model), have recently been found. The giant spontaneous polarization inhibits the polarization reversal and appearance of a large piezoelectric response. , Chemical substitution attempts in Bi 2 ZnTiO 6 , such as La 3+ for Bi 3+ , Mg 2+ for Zn 2+ , and Mn 4+ for Ti 4+ , have been made to reduce the level of spontaneous polarization. − However, the magnitudes of spontaneous polarization hardly decreased in the tetragonal phases of Bi 2– x La x ZnTiO 6 ( x < 0.3) and Bi 2 Zn 1– x Mg x TiO 6 ( x < 0.3). The crystal structure changed to the monoclinic Ia ( Cc ) phase in Bi 2 ZnTi 1– x Mn x O 6 (0.2 ≤ x ≤ 0.45).…”

Special quasirandom structures to study the(K0.5Na0.5)NbO3random alloy

“…Such random alloys represent a major challenge for first-principles calculations due to the limited size of the computational supercells that can be simulated. Typically, the structure and properties of an alloy are studied using small supercells, approximating the alloy compositions with highly ordered structures [5][6][7]. For compounds with simple ratios, like KNN, a rocksalt structure (RSS) is often used [8].…”

Bi-O covalency in PbTiO3-BiInO3 with enhanced ferroelectric properties: Synchrotron radiation diffraction and first-principles study

“…1,2 PbTiO 3 -based perovskite compounds are significant multifunction materials, which have been extensively researched in the last half century. [3][4][5] Through chemical modification, we can manipulate the physical properties of these compounds like ferroelectric, piezoelectric, and other properties. 6 Recently, Bi-based perovskites of BiMeO 3 , in which Me are cations with an average valent of þ3, have been adopted to form a binary system with PbTiO 3 , so that the high temperature ferroelectric properties are optimized.…”