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Density functional theory was used to inspect the structural properties and morphotropic phase boundaries (MPBs) of Ag1-xKxNbO3 (AKN) solid solutions. Structural properties of pristine AgNbO3 in Pbcm and Pmc21 phases were firstly investigated. The obtained crystal structures were found to be in good agreement with those from experiments. From the formation energy calculation of AKN solid solutions, the coexistences between Pbcm and Pmc21 phases and between Bmm2 and Pm phases were found to be in the composition ranges of x<"0.46" and x>"0.46," respectively. Therefore, the MPB separating the antiferroelectric and the ferroelectric phases can be specified at x ≈ "0.46." This theoretical study provides x ≈ "0.46" as a suggestive composition probably useful to acquire superior piezoelectricity for the utilization of AKN with reduced volatility of alkali elements at the A-site. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the ferroelectric property of BiAlxGa(1−x)O3withx =0.00, 0.25, 0.50, 0.75, and 1.00 for replacement of the widely use, PZT which is toxic. The techniques used are density functional theory with local density approximation (LDA) as well as projector augmented-wave method (PAW). The composition (x) was varied via setting the appropriated supercell. The solid solutions in both tetragonal (P4 mm) and rhombohedral (R3c) phase have been simulated to determine crystal stability, phase transition, and ferroelectric properties. From the results, the expected morphotropic phase boundaries (MPB) have not been observed because allR3cstructures are more energetically stable than those ofP4 mm. Therefore, Bi(Ga,Al)O3solid solution cannot display higher ferroelectricity than that of pure BiGaO3. However, the calculated polarization of Bi(Ga,Al)O3are still very high compared to other ferroelectric materials, e.g. AgNbO3and BaTiO3. This suggests that the considered solid solution could be one of lead-free candidates for future industrial applications. [ABSTRACT FROM AUTHOR]

Effects of compressive stress applied perpendicular to electric field on dielectric properties of (1-x)Pb(Zr1/2Ti1/2)O3-(x)Pb(Zn1/3Nb2/3)O3 (x = 0.1-0.5) ceramics were investigated. The results showed that the superimposed compression stress had pronounced effects on the dielectric properties of PZT-PZN ceramics. With increasing compressive stress the dielectric constant of the ceramics decreased, while the dielectric loss tangent increased. The observations were mainly interpreted in terms of competing influences of the domain switching through non-180° domain walls, clamping of domain walls, and de-aging mechanisms. Interestingly, the observed changes of the dielectric properties with the perpendicular compressive stress were generally similar to those under the parallel stress. [ABSTRACT FROM AUTHOR]

The influences of compressive stress on the dielectric properties of (1-x)Pb(Zr1/2Ti1/2)O3-(x)Pb(Co1/3Nb2/3)O3 (x = 0.1-0.5) ceramics were investigated in this study. The dielectric properties were measured under compressive stress applied parallel and perpendicular to an electric field direction. The results clearly showed that the superimposed compression stress had pronounced effects on the dielectric properties of PZT-PCN ceramics. In general, with increasing compressive stress (applied parallel with the electric field direction) the dielectric constant of the ceramics increased, while the dielectric loss tangent decreased. Interestingly, the observed changes of the dielectric properties with the perpendicular compressive stress were opposite to those under the parallel stress. [ABSTRACT FROM AUTHOR]

Effects of compressive stress on the dielectric properties of PZT-PZN ceramics with a formula (1-x) Pb(Zr1/2Ti1/2)O3-xPb(Zn1/3Nb2/3)O3 or (1-x) PZT-(x)PZN(x = 0.1-0.5) were investigated under stress up to 230 MPa. The experimental results revealed that the superimposed compression stress had pronounced effects on both the dielectric constant and the dielectric loss tangent of PZT-PZN ceramics. In addition, the dielectric properties were considerably lowered after a stress cycle. The observations were mainly interpreted in terms of domain switching through non-180° domain walls, clamping of domain walls, de-aging, and the stress induced decrease in switchable part of spontaneous polarization. [ABSTRACT FROM AUTHOR]