- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Electrical response of mixed phase (1-x)BiFeO3-xPbTiO3 solid solution: Role of tetragonal phase and tetragonality
摘要： We present the study of structural, morphological, dielectric, transport and ferroelectric properties of (1-x)BFO–xPTO solid solutions, with 0.3 ≤ x ≤ 0.6, prepared via non-conventional synthesis methods. These methods include Sol-gel and Single-step solid state method. Structural analysis revealed presence of mixed phases i.e. monoclinic (CC) and tetragonal (P4mm) phases, for all compositions showing a Morphotropic Phase Boundary. For the compositions with higher concentration of PTO, an increase in tetragonal phase fraction has been observed. Quantitative analysis showed, in general, higher value of c/a (i.e. tetragonality) for all samples as compared to the bulk PTO. The morphological analysis shows small grain size irrespective of synthesis method and composition. The low temperature frequency dependent tangent loss shows dielectric relaxation with small magnitude of dielectric constant indicating absence of extrinsic contributions. High temperature dielectric anomaly is observed around 400-500 K corresponding to magnetic phase transformation of BFO at Neel temperature which suggest the presence of magneto-electric coupling in specific compositions. Sol-gel prepared composite appeared to be more resistive than the Single-step synthesized composite and shows Arrhenius type dependence of high temperature ac conductivity. Ferroelectricity was observed in all ceramic samples which sustained high applied electric field up to 190 kV/cm. Finally, a correlation between polarization, tetragonal phase fraction and c/a ratio, has been drawn and discussed. It is concluded that c/a ratio (i.e. tetragonality) is more important parameter which can be tuned to achieve enhanced ferroelectric response as compared to the tetragonal phase fraction in (1-x)BFO–xPTO solid solutions.
关键词： Electric polarization,Non-conventional synthesis methods,Tetragonality,Morphotropic phase boundary,Ferroelectricity,Phase evolution,Dielectric anomalies
更新于2025-09-19 17:15:36
-
Enhanced dielectric and piezoelectric properties in the [001]-poled 0.25Pb(In <sub/>1/2</sub> Nb <sub/>1/2</sub> )O <sub/>3</sub> -0.43Pb(Mg <sub/>1/3</sub> Nb <sub/>2/3</sub> )O <sub/>3</sub> -0.32PbTiO <sub/>3</sub> single crystal near morphotropic phase boundary by alternating current treatment
摘要： In this paper, temperature dependance of induced dielectric and piezoelectric properties in the [001]-oriented predirect current poling (DCP) of the 0.25Pb(In1/2Nb1/2)O3-0.43Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (0.25PIN-0.43PMN-0.32PT) single crystals near morphotropic phase boundary was investigated using the alternating current treatment (ACT). By the optimized ACT conditions of 1 kV/mm at 50 Hz over 20 cycles, the dielectric permittivity (ε0) and piezoelectric coefficient (d33) at room temperature of the DCP-ACT crystal were improved to be 7120 and 2610 pC/N, which were 48% and 54% higher than that of the DCP crystal (ε0 = 4800, d33 = 1700 pC/N). Based on the temperature dependence of dielectric permittivity and dielectric loss of the DCP-ACT crystal, the induced monoclinic phases (MA and MC) were involved in the phase transition process from a rhombohedral phase to a tetragonal phase. The phase transition temperatures TR-MA of 116 °C of the DCP-ACT crystal showed about 10 °C higher than that of DCP. Meanwhile, ε0 of the DCP-ACT crystal at TR-MA and in the tetragonal phase region, at around 110 °C and 130 °C, were 160% and 390% higher than those of the DCP crystal, respectively. The ultrahigh ε0 = 17 000 of the DCP-ACT crystal at 130 °C may relate to the nanoscale heterogeneous polar-regions induced by ACT. The ACT is a promising way to enhance the dielectric and piezoelectric performance of the pre-DCP 0.25PIN-0.43PMN-0.32PT single crystals with broadened temperature range for device applications.
关键词： single crystal,piezoelectric properties,morphotropic phase boundary,alternating current treatment,dielectric properties
更新于2025-09-19 17:13:59
-
Improved ferroelectric response of pulsed laser deposited BiFeO <sub/>3</sub> -PbTiO <sub/>3</sub> thin films around morphotropic phase boundary with interfacial PbTiO <sub/>3</sub> buffer layer
摘要： (1 ? x)BiFeO3-xPbTiO3 (BF-xPT) is an interesting material for sensing and actuating devices with large polarization near the morphotropic phase boundary (MPB) (x = 0.30) in the bulk form. However, pulsed laser deposition (PLD) grown (BF-xPT) thin films usually show high electrical leakage and, hence, saturated ferroelectric hysteresis loops are only obtained at subzero temperatures. In this article, we report on high room temperature ferroelectric polarization with saturated hysteresis loops in pulsed laser deposited (BF-xPT) polycrystalline thin films of compositions near the MPB with the use of a thin buffer layer of PbTiO3 (PT). The thin films possessed a perovskite structure with excellent crystallinity and exhibit the presence of a monoclinic (Cm) phase (MA-type) for x = 0.20–0.25 and a mixture of a monoclinic (Cm) phase and a tetragonal (P4mm) phase for x = 0.30–0.35 compositions. The thin films with composition x = 0.25 exhibit a monoclinic phase and yield very large room temperature ferroelectric polarization (2Pr > 80μC/cm2), perhaps the highest room temperature ferroelectric polarization and excellent piezoelectric properties in PLD deposited (BF-xPT) thin films of near-MPB composition. Furthermore, the evolution of ferroelectricity with PT content, studied using room temperature Raman spectroscopy, reveals a correlation with lattice dynamics and stereochemical activity of Bi. Piezoforce domain analysis of the thin films reveals that ferroelectric polarization and electrical leakage in the thin films are intricately related to the type of domains present in the samples, viz., 180°, 109°, 90°, and 71° due to differences in the nature of the domain walls.
关键词： thin films,pulsed laser deposition,PbTiO3 buffer layer,ferroelectric response,BiFeO3-PbTiO3,morphotropic phase boundary
更新于2025-09-19 17:13:59
-
Structural transformations and physical properties of (1-x) Na<sub>0.5</sub>Bi<sub>0.5</sub>TiO<sub>3-x</sub> BaTiO<sub>3</sub> solid solutions near morphotropic phase boundary
摘要： Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of well-regulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1-x) Na0.5Bi0.5TiO3 - x BaTiO3 (NBT - BT) (0.00 ≤ x ≤ 0.10) solid-solution, prepared by sol-gel auto combustion technique and sintered by microwave sintering technique. With the addition of BaTiO3 into Na0.5Bi0.5TiO3, it induces a structural phase transition from R3c (a single phase) to R3c+P4mm (a dual phase) close to x = 0.06 and 0.07 and transform to a high symmetry tetragonal phase P4mm at higher compositions (x = 0.08 to 0.10) as evident from our X-ray Rietveld refinement and Raman spectroscopic results. In the prepared solid solution, an anomalous enhancement of remnant polarization (2Pr0) was observed for x = 0.06 and 0.07, which has been explained based on the existence of the MPB. On the other hand, the value of coercive field EC0 was found to be decreased linearly from x = 0.00 to 0.06; it is constant for higher compositions. Further details of the ferroelectric properties on the electric field poled samples have been studied and compared with the as-grown (unpoled) samples. We perform first-principles calculations based on density functional theory that confirm a structural transition from a rhombohedral to a tetragonal phase under increasing x.
关键词： First-principles calculations,Crystal structure,Morphotropic Phase Boundary,Microwave sintering,Lead-free ferroelectric materials,Electrical properties,NBT-BT solid solution
更新于2025-09-09 09:28:46