Papers by Keyword: PMN-PT

Abstract: The capacitance of (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-xPT) [001]-oriented single crystal was examined as a function of temperature and applied external dc electric field. The phase transition temperatures under the applied electric field were measured upon cooling the crystal (zero-field heating field-cooling condition) from paraelectric cubic phase. From these data, temperature versus electric field phase diagram of PMN-xPT crystal have been constructed and discussed.

Abstract: Research in renewable and clean energy has reached an unprecedented magnitude owing to the growing concerns over environmental hazards caused by the traditional fuels. In this regard, solar, wind and tidal energies are considered to meet large scale energy requirements. Small, stand-alone electronic devices which are growing in numbers in next generation smart cities, can be powered by scavenging energy from sources which would otherwise remain unused, such as mechanical vibrations. The source of mechanical vibration could have diverse origins, ranging from vibrations of machines to flow of wind, motion of automobiles, and human footfall etc. Energy harvesting from the above sources can be achieved through the principle of piezoelectricity. In the present work, piezoelectric ceramic (1-x) Pb (Mg_1/3Nb_2/3O₃)-xPbTiO₃ at x = 0.3 was prepared using conventional solid state method. Lead magnesium niobate and lead titanate (PMN-PT) solid solution within the morphotropic phase boundary composition considerably fulfils the essential piezoelectric characteristics for a high energy density harvester. However, PMN-PT is brittle and thus difficult to assemble directly into an energy harvesting system. Hence flexible piezoelectric composite of 20 wt % PMN-PT and polydimethylsiloxane (PDMS) was fabricated to evaluate its energy harvesting capability. Structural and microstructural characterization of the synthesized composite were performed using x-ray diffraction and optical microscopy. Electrical characterization was carried out using Keithley 6517B high resistance electrometer.

Abstract: The aging characteristics and influence of electric field poling on the phase transitions in (1-x)Pb (Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-xPT) [110]-oriented single crystal were examined through temperature dependent complex capacitance study. In addition to two phase transition anomalies exhibited by the crystal in the virgin state, other phase transition instabilities were observed in the complex capacitance of the crystal under the external applied electric field. The aging behavior deviated from the linear logarithmic law and followed the stretched exponential expression typical for relaxor ferroelectrics. Moreover, aging decreased with frequency while it became faster with increase in temperature towards the paraelectric – ferroelectric structural phase transition temperature.

Abstract: In the presented work composite ferroelectric/ferrimagnetic ceramics have been obtained and described. The investigated material is based on PMN-PT powders and Ni-Zn ferrite powder. The Powders of ferroelectric component (i.e. (1–x)PMN-(x)PT with x from 0.25 to 0.40 with step 0.03 were synthesized using the sol-gel method. The magnetic component i.e. nickel-zinc ferrite was obtained from oxides using the classic method of obtaining ceramics. The compositions of PMN–PT used by us have rhombohedral or tetragonal symmetries, or belong to morphotropic region. The final ceramic composite samples were obtained using the classic method of ceramic technology with calcination route and final pressureless densification using free sintering. In this paper, XRD, EDS dielectric and magnetic properties have been investigated and described for the obtained composite ceramic samples.

Abstract: La-doped Pb(Mg1/3Nb2/3)0.67Ti0.33O3 ceramics were fabricated by a two-stage sintering method from conventional raw materials. The effects of La doping on the phase structure and electrical properties of ceramics were investigated. X-ray diffraction analysis showed that the pyrochlore phase increased with the increase of La-doping level. The effects of La doping on the dielectric, ferroelectric and piezoelectric properties of the ceramics were also investigated. The results showed that La doping seriously weakened the electrical properties of the ceramics. The ceramics possess optimum properties (d33=239pC/N, Pr=10.6μC/cm2, Ec=8.5kV/cm, tanδ=0.029, εr = 2250) when the doping level is low (x = 0.02).

Abstract: The concept of energy harvesting works towards developing self-powered devices that do not require replaceable power supplies. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with ferroelectric materials. Ferroelectric materials have a crystalline structure that provide a unique ability to convert an applied electrical potential into a mechanical strain or vice versa. Based on the properties of the material, this paper investigates the technique of power harvesting and storage.

Abstract: High-resolution Brillouin scattering technique was applied to study the dynamics of central peaks (CPs) in two relaxor ferroelectric systems, PLZT-x/65/35 ceramics and PMN-33%PT [001] single crystals, respectively. It was found that CPs appear very close to an intermediate temperature, Td, for both type of specimens. The temperature dependence of CPs was attributed to the appearance and subsequent growth of polar nanoregions (PNRs) intrinsic to relaxor materials.

Abstract: In this work, effects of compressive stress on the ferroelectric properties of 0.7PMN–0.3PT ceramics were investigated. The ceramics with the formula (0.7)Pb(Mg1/3Nb2/3)O3-(0.3)PbTiO were prepared by a conventional mixed-oxide method. The ferroelectric properties under compressive stress were observed at stress up to 80 MPa using a compressometer in conjunction with a modified Sawyer-Tower circuit. The results showed that applied stress had a significant influence on the ferroelectric properties of 0.7PMN–0.3PT ceramics. Ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis (P-E) loop, the saturation polarization (Psat), the remanent polarization (Pr) and loop squareness (Rsq), decreased with increasing compressive stress, while the coercive field (Ec) remained relatively constant. Stress-induced domain wall motion suppression and non-180oC ferroelectric domain switching processes are responsible for the changes observed.

Abstract: Relaxor-based ferroelectrics, 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT) with a pyrochlore-free phase, was prepared by a modified polymerized complex process. The reactive columbite (MgNb2O6) phase was synthesized by the polymerized complex method at 1050oC for 4 h with 3wt% excess MgO. Lead acetate and tetrebutyl titanate were used to synthesize pyrochlore-free PMN-PT powder via the columbite route, from 800oC to 900oC, in air for 4 h. X-ray diffraction and scanning electron microscopy were used to detect the perovskite phase evolution and the presence of the pyrochlore phase in PMN-PT. The formation of perovskite PMN-PT is a function of the time and temperature conditions of the precursor calcinations, and an optimum condition for the thermal decomposition of the precursor was determined to avoid the formation of the pyrochlore phase.

Abstract: Lead magnesium niobate-lead titanate (0.8Pb(Mg1/3Nb2/3)O3-0.2PbTiO3, PMN-PT) thick films in the thickness range about 75 μm have been successfully fabricated on Au-coated Al2O3 substrates by electrophoretic deposition (EPD). Non-aqueous colloidal suspensions suitable for EPD were prepared by mixing ultrasonically PMN-PT particles in ethanol with pH=6.0. The effect of EPD process parameters such as deposition voltage, deposition time and the specific deposition mass of PMN-PT particles were investigated. The EPD parameters were optimized in order to obtain crack-free, high-quality uniform ceramic films. The deposited pyrochlore-free PMN-PT thick films were sintered at 1000oC for 30 min, and the phase evolvement and the microstructure of the film were characterized by X-ray diffraction and scanning electron microscope.