Effects Of Poling Conditions Research Articles

Piezoelectric PVDF‐TrFE nanocomposite mats filled with BaTiO3 nanofibers: The effect of poling conditions

AbstractBaTiO3 nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF‐TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β‐crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two‐step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d33 (−31.7 pC N−1), strongly dependent on the added BaTiO3 nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices.

The effect of poling conditions on the performance of piezoelectric energy harvesters fabricated by wet chemistry

The effect of poling conditions on the power output of piezoelectric energy harvesters using sol–gel based Pb(Zr0.53,Ti0.47)O3–Pb(Zn1/3,Nb2/3)O3 piezoelectric thin-films has been investigated.

Effects of Polarization on the Strontium Ferrite Modified 0-3 Cement-Based Piezoelectric Composite

Strontium ferrite modified 0-3 cement-based piezoelectric composites were produced with piezoelectric ceramic [0.08Pb(Li1/4Nb3/4)O•0.47PbTiO3•0.45PbZrO3], sulphoaluminate cement and strontium ferrite by compressing technique, and the effects of poling conditions on the piezoelectric and dielectric properties were investigated. In order to contrast, a unmodified 0-3 cement-based piezoelectric composite was fabricated. The results show that the higher the poling electric field, the longer the poling time and the higher the poling temperature, the composites have the higher piezoelectric strain factor d33, piezoelectric voltage factor g33, dielectric constant εr and dielectric loss tanδ， and the strontium ferrite modified composites are polarized more easily, and have better properties than the unmodified composites. In the meantime, the optimum poling conditions were obtained, and the optimum poling field E, poling time t and poling temperature T were 5 kV/mm, 20 min and 80 °C.

Enhanced piezoelectricity and high temperature poling effect in (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 ceramics via an ethylene glycol route

A solution chemical method utilizing ethylene glycol as solvent has been developed to prepare the ceramics of (1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3[(1−x)PMN–xPT] from a precursor powder that can be pressed and fired in one step to produce high quality ceramics with excellent piezoelectric properties. The ceramics reach a relative density of up to 97% of the theoretical value after direct calcinations. This high density is achieved without the need of additional sintering after calcination which is usually required in conventional solid state syntheses to produce ceramics. The ceramics exhibit a unipolar piezoelectric coefficient d33 of 848 pC/N, which is one of the highest values for any unmodified/untextured binary systems reported to date. Since the piezoelectric properties depend on composition and electric field, the effect of poling conditions was investigated. A critical temperature limit has been found, above which poling can dramatically impair the piezoelectric properties due to a field-induced increase in the monoclinic phase component around the morphotropic phase boundary.

Effect of poling condition on piezoelectric properties of (K 0.5Na 0.5)NbO 3–LiNbO 3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics 0.94(K 0.5Na 0.5)NbO 3–0.06LiNbO 3 (abbreviated as KNLN6) have been synthesized by traditional ceramics process without cold-isostatic pressing. The phase behavior before poling and after poling was analyzed. The results show that the orthorhombic and tetragonal phase co-exist in KNLN6 ceramics. The effect of poling conditions on piezoelectric properties of KNLN6 ceramics was investigated. The physics mechanism was also discussed. The results show that the optimum poling condition for KNLN6 ceramics is poling electric field of 3.5 kV/mm, poling temperature of 120 °C and poling time of 30 min. Piezoelectric properties of KNLN6 ceramics under the optimum poling condition is piezoelectric constant d 33 of 215 pC/N, planar electromechanical coupling factor k p of 0.38, thickness electromechanical coupling factor k t of 0.48, and Curie temperature T c of 450 °C, respectively. The results show that KNLN6 ceramics is an excellent candidate for lead-free piezoelectric ceramics.

Effect of poling condition on piezoelectric properties of (K 0.5Na 0.5)NbO 3 ceramics

The lead-free piezoelectric ceramics (K 0.5Na 0.5)NbO 3 (abbreviated as KNN) with the relative density of 97.6% were synthesized by press-less sintering owing to the careful control of processing conditions. The phase structure of KNN ceramics was analyzed. The results show that the pure perovskite phase with orthorhombic symmetry is in all ceramics specimens. The effect of poling conditions on the piezoelectric properties of KNN ceramics was investigated. The results show that the piezoelectric constant d 33 and electromechanical coupling factor k p, increase with poling field, poling temperature and poling time increasing, then decrease because of electric broken. Take into account of poling conditions and piezoelectric properties of pure KNN ceramics, the optimum poling conditions for pure KNN ceramics are poling field of 4 kV/mm, poling temperature of 140 °C and poling time of 20–25 min.

Effect of poling field and temperature on dielectric and piezoelectric property of 〈0 0 1〉-oriented 0.70Pb(Mg 1/3Nb 2/3)O 3–0.30PbTiO 3 crystals

Effect of poling conditions (different poling fields and temperatures) on dielectric and piezoelectric property of 〈0 0 1〉-oriented 0.70Pb (Mg 1/3Nb 2/3)O 3–0.30PbTiO 3 crystal was investigated. The results show, that it is easy for the crystal to be full poled in high temperature, while it is difficult for the crystal in low temperature. An appropriate poling condition for the crystals is suggested.

Effect of poling conditions on growth of calcium phosphate crystal in ferroelectric BaTiO3 ceramics.

Recently, ceramic materials have been given a lot of attention as candidates for implant materials, since they possess biologically favorable characteristics for osseointegration. Among them, BaTiO3 (BTO) ceramics are ferroelectric and piezoelectric after poling treatments. However, little or no information is available on the poling condition of BTO and their effect on calcium phosphate (CaP) formation. In this study, the effect of poling conditions on the formation of CaP layer was investigated. It was observed from this study that CaP was formed on negatively charged BTO surfaces. An increase in Ca/P ratio to 1.67 was observed when the poling temperature was increased above the Curie temperature. On positively charged BTO, no CaP layer was observed.

An investigation of the effect of poling conditions on the characteristics of screen‐printed piezoceramics

A study of the effect of poling conditions on screen‐printed piezoceramics was undertaken. Printable pastes were produced, using a commercially available lead zirconate titanate (PZT) powder, mixed with two types of binder, lead (II) oxide and a lead borosilicate glass. Sample devices were fabricated using the two paste types and processed, using standard thick film techniques, before being poled under varying conditions. Samples were compared by measurement of piezoelectric charge constant, d33 and using scanning electron microscopy techniques. Temperature and time are shown to increase poling efficiency, while poling field reaches an optimum at 2‐3 MV m‐1. The PZT layers start to fail through a process of dielectric breakdown at fields of 3.5 MV m‐1 and above.

Effect of poling conditions on second-harmonic generation in fused silica

A systematic study of the effects of poling time and applied voltage on second-harmonic (SH) generation in thermally poled silica glass reveals that the SH signal is proportional to the square of the applied voltage and that the speed of the poling process increases with the applied voltage. Prior treatment of the samples is found to affect the poling process, and the optimum poling conditions are observed to depend on the poling atmosphere. The mechanism of thermal poling is discussed in the light of these new results.

Tensile Stress-Strain Behavior of Piezoelectric Ceramics

Fracture strength and stress-strain behavior under tensile stress in piezoelectric ceramics have been investigated with special emphasis on the effects of poling conditions. The materials used in this work are the commercial piezoelectric ceramics, PbZrO3-PbTiO3 (PZT) and BaTiO3. First, an attempt was made to evaluate the tensile strength properties of samples having a specially designed specimen geometry. In the actual tensile test, fracture did not occur at the gripping portion at all, indicating usefulness of the present tensile test method. Not only fracture strength, but also elastic properties, tensile modulus and Poisson's ratio, were evaluated. Second, an investigation was performed on the stress-strain behavior under tension in this material. As a result, stress-strain response under tension was confirmed to be nonlinear. The nonlinearity in the stress-strain relationship under compression loading has already been reported by some investigators. However, very little work has been done on the tensile stress-strain relationship studied in this paper. Third, acoustic emission monitoring was performed simultaneously during tensile tests, and thus the tensile failure process in piezoelectric ceramics was discussed.

Spatial distributions of polarization and space charge in tin-substituted lead zirconate titanate ceramics using laser intensity modulation method (LIMM)

A new method for measuring the spatial distribution of combined polarization and space charge in poled polymer electrets was recently developed. The technique, called the Laser Intensity Modulation Method (LIMM), was modified in the present study in order that it could be used with ferroelectric ceramic samples having thicknesses of the order of 1 mm rather than the tens of micrometers found in conventional polymer films. PZT ceramics with a high Sn content and with compositions close to the Zr phase boundary were studied. The effects of poling conditions on polarization and space charge distributions in the two ferroelectric phases were examined. The polarization distributions were highly nonuniform, being flat in the central regions and diminishing strongly in the regions close to the electrodes. This was true even in samples poled to saturation. Large amounts of space charge were observed in the central regions. Pyroelectric coefficients and spontaneous polarizations were also measured.

Piezoelectric properties of modified PZT ceramics

The influence of impurities on piezoelectric parameters such as the radial coupling factor kr and mechanical quality factor Qm have been measured. A mechanism of internal friction is proposed. The effects of the interaction of 90 degrees domain walls with defects introduced by impurities are explained. A-site vacancies reduce the local stress in a domain, making it become remarkably mobile. The easy motion of the domain wall causes the internal friction in the ceramics to increase and thus Qm to decrease. O-site vacancies act as pinning points for the domain walls, so that domain wall motion is reduced when O-site vacancies are dominant, and Qm is raised due to the reduced internal friction. The effect of poling conditions is also discussed.

Temperature dependence of the pyroelectric response of vinylidene fluoride trifluoroethylene copolymer and the effect of its poling conditions

Vinylidene fluoride trifluoroethylene copolymer VDF-TrFE was found to be pyroelectric when poled by application of dc high field. Temperature dependence of its pyroelectric response and the effects of poling conditions were investigated. It was shown that there existed a critical temperature at 70 °C above which pyroelectricity vanished. The pyroelectric coefficient increased with the increase in poling temperature with a tendency to saturation. The pyroelectric coefficient of these samples poled above 70 °C were constantly 9 nc/cm2 K, which is significantly larger than that of any other polymers.

Effects of poling conditions on responsivity and uniformity of polarization of PVF2 pyroelectric detectors

A large number of pyroelectric detectors, fabricated from commercially available PVF2 and poled under a variety of conditions of voltage, temperature, and time have been evaluated for responsivity and uniformity of polarization in the direction of the poling field. Results show that uniformity of polarization (a requirement for flat frequency response) can be achieved and responsivities as high as 2.9 μA/W can be obtained.