Phase transitions and local polarity above TC in a PbZr0.87Ti0.13O3 single crystal

Solid solutions of PbZr1_xTixO3 (PZT) are one of the most widely used piezoelectric materials with perovskite structure. Despite the decades of research, the phase diagram of PZT reported in 1971 has not been resolved yet. Recently, it turned out that single crystals of good quality of these solid solutions can be grown. By means of top-seeded solution growth (TSSG) technique, we succeeded to grow a single PbZr0.87Ti0.13O3 crystal. Hence, a partial verification of the diagram could be performed through investigations of the optical, dielectric, pyroelectric and elastic properties of this crystal, in a wide temperature range. The obtained results confirmed that the PbZr0.87Ti0.13O3 crystal undergoes a sequence of phase transitions, such as those observed in ceramics of similar chemical composition. However, additional anomalies of investigated physical properties were observed and discussed. Moreover, the influence of electric field on optical properties has been investigated for the first time and has proven the existence of local polar character of the phase above TC in a limited temperature range

Piezoelectric and elastic properties of relaxor-like PZT:Ba ceramics

The solid solutions of PbZr1-xTixO3 (PZT) are the most known and widely applicable piezoelectric ceramic materials. The influence of different dopants on PZT properties has been studied for many years. Some of such compositions have revealed a behavior typical for ferroelectric relaxors. In the case of Pb0.75Ba0.25Zr0.70Ti0.30O3 ceramics (abbreviation PBZT 25/70/30), prepared by mixed-oxide processing technique elastic, it was found that macroscopic piezoelectric activity is present far above the temperature at which structural changes and maximum of permittivity occur in unpoled samples (~ 200 °C). Anomalies of the elastic and piezoelectric properties have been observed very clearly near the temperature of 152 °C. Within the temperature range of 152–220 °C, unstable piezoelectric properties have been detected due to the existence of polar micro/nano-clusters and non-trivial elastic-electric interactions between them, through the non-polar paraelectric matrix. The origin of such interactions could be lattice instabilities, dynamic change in polar cluster sizes, and fluctuations in chemical composition. Based on the results of the research, it can be said that PZT ceramics of such composition is a relaxor-like material and it is not a ferroelectric relaxor

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements

The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO3) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO3 single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results. There is no melting process in the SSCG method, thus the crystal grown using a SSCG method have inherent higher levels of impurity and defect concentrations, which is a good candidate for investigating the effect of crystal quality on the precursor phenomena. The acoustic, dielectric, and piezoelectric properties, as well as birefringence, of the SSCG-grown BaTiO3 were examined over a wide temperature range. Especially, the acoustic phonon behavior was investigated in terms of Brillouin spectroscopy, which is a complementary technique to Raman spectroscopy. The obtained precursor anomalies of the SSCG-grown BaTiO3 in the cubic phase were similar to those of other single crystals, in particular, of high-quality single crystal grown by top-seeded solution growth method. These results clearly indicate that the observed precursor phenomena are common and intrinsic effect irrespective of the crystal quality

Strong piezoelectric properties and electric-field-driven changes in domain structures in a PbZr0.87Ti0.13O3 single crystal

PbZr 1-x Tix O3 perovskite materials, known as PZT, are highly applicable, mainly due to their extraordinary piezoelectric properties. Recently, a technology of PZT crystals growth has been elaborated and opened new investigation possibilities for these compounds. In this paper, we demonstrate a highly piezoelectric response in PbZr 0.87 Ti 0.13 O3 single crystal. Under the action of an electric field, the piezoelectric coefficient d 33 turns out to be over 2500 pm V -1. The optical studies performed have proved a significant influence of the domain dynamics on such high-efficiency piezoelectric response. Monoclinic M and rhombohedral R phases have been observed in the lead zirconate-titanate crystals with a low Ti content. This coex- istence of phases with different symmetries and dense domain walls are the primary sources of high piezoelectric response. We have observed that strong electric fields may act on randomly oriented po- larization vectors so that the total piezoelectric activity disappears, and the unusual isotropization point near 250 °C appears

Transparent EuTiO3 films : a possible two-dimensional magneto-optical device

The magneto-optical activity of high quality transparent thin films of insulating EuTiO3 (ETO) deposited on a thin SrTiO3 (STO) substrate, both being non-magnetic materials, are demonstrated to be a versatile tool for light modulation. The operating temperature is close to room temperature and allows for multiple device engineering. By using small magnetic fields birefringence of the samples can be switched off and on. Similarly, rotation of the sample in the field can modify its birefringence Δn. In addition, Δn can be increased by a factor of 4 in very modest fields with simultaneously enhancing the operating temperature by almost 100 K

Monoclinic domain populations and enhancement of piezoelectric properties in a PZT single crystal at the morphotropic phase boundary

The origin of the strong piezoelectric phenomenon in PbZr1−xTixO3 (PZT) perovskites still suffers from a lack of complete understanding. It concerns the distinction between the intrinsic and extrinsic mechanisms that govern PZT's piezo activity. These two mechanisms have been investigated in single crystal PbZr0.54Ti0.46O3 at the morphotropic phase boundary. After poling in a DC electric field, the piezoelectric properties were examined on the same crystal by observing piezoelectric resonances to determine the piezoelectric coefficient d31 and measuring quasistatic deformation to determine the coefficient d33. The domain populations were investigated during and after poling in a DC electric field. These populations were also investigated as a function of DC fields for strengths similar to those used to measure quasistatic piezoelectric properties for a poled crystal. The experiments indicate that the intrinsic origin of the enhancement of the piezoelectric properties is connected with a change in the population of domains with monoclinic symmetry, in which there is an easy polarization rotation under the action of the electric field

Ultrahigh Piezoelectric Strains in PbZr1−xTixO3 single crystals with controlled Ti content close to the tricritical point

Intensive investigations of PbZr Ti O (PZT) materials with the ABO perovskite structure are connected with their extraordinary piezoelectric properties. Especially well known are PZT ceramics at the Morphotropic Phase Boundary (MPB), with x~0.48, whose applications are the most numerous among ferroelectrics. These piezoelectric properties are often obtained by doping with various ions at the B sites. Interestingly, we have found similar properties for undoped PZT single crystals with low Ti content, for which we have confirmed the existence of the tricritical point near x~0.06. For a PbZr Ti O crystal, we describe the ultrahigh strain, dielectric, optical and piezoelectric properties. We interpret the ultrahigh strain observed in the region of the antiferroelectric-ferroelectric transition as an inverse piezoelectric effect generated by the coexistence of domains of different symmetries. The complex domain coexistence was confirmed by determining optical indicatrix orientations in domains. The piezoelectric coefficient in this region reached an extremely high value of 5000 pm/V. We also verified that the properties of the PZT single crystals from the region near the tricritical point are incredibly susceptible to a slight deviation in the Ti content

The Electrodegradation Process in PZT Ceramics under Exposure to Cosmic Environmental Conditions

Long-time electric field action on perovskite piezoelectric ceramic leads to chemical degradation. A new way to accelerate the degradation is the exposure of the ceramic to DC electric fields under a vacuum. A high-quality commercial piezoelectric material based on PbZr1−xTixO3 is used to study such impacts. To avoid the influence of ferroelectric properties and possible removal of oxygen and lead oxides during the degradation process, the experiments are in the temperature interval of 500 °C > T > TC. Changes in resistance during the electrodegradation process is an electrically-induced deoxidation, transforming the ceramic into a metallic-like material. This occurs with an extremely low concentration of effused oxygen of 1016 oxygen atoms per 1 cm3. Due to this concentration not obeying the Mott criterion for an isolator-metal transition, it is stated that the removal of oxygen mostly occurs along the grain boundaries. It agrees with the first-principle calculations regarding dislocations with oxygen vacancies. The decrease in resistivity during electrodegradation follows a power law and is associated with a decrease in the dislocation dimension. The observed reoxidation process is a lifeline for the reconstructing (self-healing) properties of electro-degraded ceramics in harsh cosmic conditions. Based on all of these investigations, a macroscopic and nanoscopic model of the electrodegradation is presented

2015/16 I-MOVE/I-MOVE+ multicentre case-control study in Europe: Moderate vaccine effectiveness estimates against influenza A(H1N1)pdm09 and low estimates against lineage-mismatched influenza B among children

BACKGROUND: During the 2015/16 influenza season in Europe, the cocirculating influenza viruses were A(H1N1)pdm09 and B/Victoria, which was antigenically distinct from the B/Yamagata component in the trivalent influenza vaccine. METHODS: We used the test-negative design in a multicentre case-control study in twelve European countries to measure 2015/16 influenza vaccine effectiveness (VE) against medically attended influenza-like illness (ILI) laboratory-confirmed as influenza. General practitioners swabbed a systematic sample of consulting ILI patients and a random sample of influenza-positive swabs was sequenced. We calculated adjusted VE against influenza A(H1N1)pdm09, A(H1N1)pdm09 genetic group 6B.1 and influenza B overall and by age group. RESULTS: We included 11 430 ILI patients, of which 2272 were influenza A(H1N1)pdm09 and 2901 were influenza B cases. Overall VE against influenza A(H1N1)pdm09 was 32.9% (95% CI: 15.5-46.7). Among those aged 0-14, 15-64 and ≥65 years, VE against A(H1N1)pdm09 was 31.9% (95% CI: -32.3 to 65.0), 41.4% (95% CI: 20.5-56.7) and 13.2% (95% CI: -38.0 to 45.3), respectively. Overall VE against influenza A(H1N1)pdm09 genetic group 6B.1 was 32.8% (95% CI: -4.1 to 56.7). Among those aged 0-14, 15-64 and ≥65 years, VE against influenza B was -47.6% (95% CI: -124.9 to 3.1), 27.3% (95% CI: -4.6 to 49.4) and 9.3% (95% CI: -44.1 to 42.9), respectively. CONCLUSIONS: Vaccine effectiveness (VE) against influenza A(H1N1)pdm09 and its genetic group 6B.1 was moderate in children and adults, and low among individuals ≥65 years. Vaccine effectiveness (VE) against influenza B was low and heterogeneous among age groups. More information on effects of previous vaccination and previous infection is needed to understand the VE results against influenza B in the context of a mismatched vaccine.ECDC has contributed fund for the coordination and some study sites under the Framework contract no. ECDC/2014/026 for the individuals aged less than 65 years. The I‐MOVE/I‐MOVE+ study team is very grateful to all patients, general practitioners, paediatricians, hospital teams, laboratory teams and regional epidemiologists who have contributed to the study. We acknowledge the authors, originating and submitting laboratories of the sequences from GISAID's EpiFlu Database used for this study. All submitters of data may be contacted directly via the GISAID website http://www.gisaid.org.S

2015/16 I-MOVE/I-MOVE+ multicentre case-control study in Europe: Moderate vaccine effectiveness estimates against influenza A(H1N1)pdm09 and low estimates against lineage-mismatched influenza B among children

Background: During the 2015/16 influenza season in Europe, the cocirculating influenza viruses were A(H1N1)pdm09 and B/Victoria, which was antigenically distinct from the B/Yamagata component in the trivalent influenza vaccine. Methods: We used the test-negative design in a multicentre case-control study in twelve European countries to measure 2015/16 influenza vaccine effectiveness (VE) against medically attended influenza-like illness (ILI) laboratory-confirmed as influenza. General practitioners swabbed a systematic sample of consulting ILI patients and a random sample of influenza-positive swabs was sequenced. We calculated adjusted VE against influenza A(H1N1)pdm09, A(H1N1)pdm09 genetic group 6B.1 and influenza B overall and by age group. Results: We included 11 430 ILI patients, of which 2272 were influenza A(H1N1)pdm09 and 2901 were influenza B cases. Overall VE against influenza A(H1N1)pdm09 was 32.9% (95% CI: 15.5-46.7). Among those aged 0-14, 15-64 and ≥65 years, VE against A(H1N1)pdm09 was 31.9% (95% CI: −32.3 to 65.0), 41.4% (95% CI: 20.5-56.7) and 13.2% (95% CI: −38.0 to 45.3), respectively. Overall VE against influenza A(H1N1)pdm09 genetic group 6B.1 was 32.8% (95% CI: −4.1 to 56.7). Among those aged 0-14, 15-64 and ≥65 years, VE against influenza B was −47.6% (95% CI: −124.9 to 3.1), 27.3% (95% CI: −4.6 to 49.4) and 9.3% (95% CI: −44.1 to 42.9), respectively. Conclusions: Vaccine effectiveness (VE) against influenza A(H1N1)pdm09 and its genetic group 6B.1 was moderate in children and adults, and low among individuals ≥65 years. Vaccine effectiveness (VE) against influenza B was low and heterogeneous among age groups. More information on effects of previous vaccination and previous infection is needed to understand the VE results against influenza B in the context of a mismatched vaccine