Relaxor Pb(Mg1/3Nb2/3)O3: A Ferroelectric with Multiple Inhomogeneities (original) (raw)
Related papers
2011
The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B0 1=3B00 2=3)O3-type complex perovskite relaxors, are rather
High-T m relaxor ferroelectrics: 0.3BiScO 3 – 0.6PbTiO 3 – 0.1Pb " Mn 1Õ3 Nb 2Õ3 …O 3
High-T m relaxor materials are being developed for high-temperature high-power density electrotransduction applications and high-temperature capacitors in automobile applications. A relaxor ferroelectric material of composition 0.3BiScO 3 -0.6PbTiO 3 -0.1Pb(Mn 1/3 Nb 2/3 )O 3 having a very high dielectric maximum of ϳ350°C is reported. The relaxor behavior is confirmed by studying polarization relaxation and frequency and temperature dependent dielectric behavior. The dielectric constant in the low-temperature region of 10°CϽTϽ150°C is found to be independent of the frequency with a temperature gradient of ץ/ץTϭ2.5/°C. The room-temperature magnitude of dielectric constant is ϳ600.
The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B 0 1=3 B 00 2=3 )O 3 -type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg 1/3 Nb 2/3 )O 3 -based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase.
Japanese Journal of Applied Physics, 2001
The Brillouin back-scattering spectra, dielectric permittivities, polarization–electric field (P–E) hysteresis loops and domain structures have been measured as a function of temperature in a relaxor-based ferroelectric single crystal (PbMg1/3Nb2/3O3)0.69(PbTiO3)0.31 (PMN–31%PT). In order of increasing temperature, PMN–31%PT undergoes successive phase transitions: rhombohedral phase (below ∼370 K) →coexistence of rhombohedral and tetragonal phases (between ∼370 and ∼380 K) →tetragonal phase (between ∼380 and ∼400 K) →coexistence of tetragonal and cubic phases (betwee ∼400 and ∼420 K) →cubic phase (above ∼420 K). An extra ferroelectric anomaly of the dielectric permittivity appears at 370 K possibly due to the percolating polar cluster induced by an external electric field. It was found that different individual domain regions have different transition temperatures. This phenomenon suggests an inhomogeneous distribution of Ti4+ concentration in the PMN–31%PT crystal. The dielectric p...
Anomalous phase in the relaxor ferroelectricPb(Zn1∕3Nb2∕3)O3
Physical Review B, 2004
X-ray diffraction studies on a Pb(Zn 1/3 Nb 2/3)O3 (PZN) single crystal sample show the presence of two different structures. An outer-layer exists in the outer most ∼ 10 to 50 µm of the crystal, and undergoes a structural phase transition at the Curie temperature TC ≈ 410 K. The inside phase is however, very different. The lattice inside the crystal maintains a cubic unit cell, while ferroelectric polarization develops below TC. The lattice parameter of the cubic unit cell remains virtually a constant, i.e., much less variations compared to that of a typical relaxor ferroelectric, in a wide temperature range of 15 K to 750 K. On the other hand, broadening of Bragg peaks and change of Bragg profile line-shapes in both longitudinal and transverse directions at TC clearly indicate a structural phase transition occurring.
Universal relaxor polarization in Pb (Mg_ {1/3} Nb_ {2/3}) O_ {3} and related materials
2002
T m and γ ≅ 2, for all the three compositions studied. The universal relaxor susceptibility is attributed to the polarization of polar nanoregions, which are inherent in the relaxor ferroelectrics. A microscopic model of this polarization is proposed, according to which the dipole moments of some ('free') unit cells inside polar nanoregion can freely choose several different directions, while the direction of the total moment of the nanoregion remains the same. The ensemble of interacting polar nanoregions is described in terms of a standard spherical model, which predicts the quadratic divergence of susceptibility above the critical temperature, in agreement with the experimental results.
Ferroelectrics Letters Section, 2001
Polarization-electric field (P-E) hysteresis loops and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystal (PbZn,/3Nb2/303)0.9~j(PbTi03)o.o~s (PZN-8.5%PT). In order of increasing temperature, PZN-8.5%PT undergoes successive phase transitions: rhombohedra1 phase (below-375 K) + coexistence of rhombohedral and tetragonal phases (between-375 and-390 K)-f tetragonal phase (between-390 and-420 K)-+ coexistence of tetragonal and cubic phases (between-420 and-460 K)-+ cubic phase (above-460 K). Phase coexistence suggests an inhomogeneous distribution of Ti4+ concentration in the PZN-8.5%PT crystal.
2009
The 1:1 B-site cation order in Pb͑Mg 1/3 Nb 2/3 ͒O 3 relaxor ferroelectric ceramics was significantly enhanced by doping of minor amounts of La 3+ , Sc 3+ , or W 6+ ͑less than 3 at. %͒ combined with a slow cooling procedure. Transmission electron microscopy examination confirmed the size increase of the cation-ordered regions embedded in a disordered matrix in the samples that were slowly cooled after sintering. The average cation ordering parameter ͑S͒ determined from x-ray diffraction data in these partially ordered samples was about 0.3-0.4. The ferroelectric properties and dielectric relaxation were compared in partially ordered and disordered ͑S =0͒ samples with the same composition. It was found that typical relaxor behavior was preserved in partially ordered ceramics. Furthermore, the temperature and diffuseness of the characteristic relaxor permittivity peak and the parameters of dielectric relaxation ͑in particular, the distribution of relaxation times and the Vogel-Fulcher freezing temperature͒ were practically independent of S. In contrast, the diffuseness of the phase transition from the ferroelectric phase ͑induced by external electric field͒ to the ergodic relaxor phase appeared to be much larger in the disordered samples than in the partially ordered ones ͑this diffuseness was assessed using pyroelectric current and ferroelectric hysteresis loops͒. These results suggest that cation ordering did not influence the behavior of polar nanoregions which are responsible for the dielectric response in the ergodic relaxor phase but significantly influenced the ferroelectric phase transition. The results are interpreted in terms of different types of polar regions in the disordered matrix and cation-ordered domains.