Polarization-electric Field Measurements Research Articles

Novel High Power Piezoelectrics for Transformers and Actuators

ABSTRACTThis letter reports a Pb(Zr0.5Ti0.5)O3 (PZT) based composition, which provides high dielectric, piezoelectric and electromechanical properties. The composition corresponding to 0.2 PZN – 0.8 PZT + 0.5 wt% MnO2 provides the radial mode coupling factor (kp) of 0.58, longitudinal mode piezoelectric constant (d33) of 277 pC/N, dielectric constant (ε33/εo) of 946 and mechanical quality factor (Qm) of 1402. X-ray diffraction, dielectric and polarization-electric field measurements were done to investigate the origin for this high performance. It was found that high soft properties are obtained due to the shifting of PZT composition towards morphotropic phase boundary (MPB) and high hard properties are obtained due to the generation of dipolar defects which pin the polarization. The properties of the composition corresponding to 0.9 PZT – 0.1PMnN (Zr/Ti = 0.51/0.49) modified with 6 mol% Sr were found to be: kp = 0.53, Qm = 800, d33 = 274, ε33/εo = 1290 and tanδ = 1.1 %, with a TCF of -8 ppm/oC (-20 to 80°C). High piezoelectric properties with low TCF shows the suitability of this composition for ultrasonic devices used under fluctuating thermal environment.

Effects of titanium and tantalum adhesion layers on the properties of sol-gel derived SrBi2Ta2O9 thin films

The effects of titanium (Ti) and tantalum (Ta) adhesion layers on the ferroelectric and microstructural properties of sol-gel-derived SrBi2Ta2O9 (SBT) films are investigated. It is found that the atoms from the adhesion layer play a significant role in the resultant microstructures and physical properties of SBT films. The electron spectroscopy for chemical analysis clearly indicates that both the Ti and Ta atoms of adhesion layers have out-diffused behavior onto the surface of bottom-electrode Pt films after a thermal treatment of 750 °C, 1 min. Various out-diffused species do cause the distinct properties of SBT films, which are confirmed by the results of surface analysis and polarization-electric field (P-E) measurements. The formation of undesirable second phase compounds near the SBT/PT interface has been observed in specimens with Ti layer, and it is speculated to be the significant degradation of spontaneous polarization. On the contrary, Ta species are found to exhibit the pure bismuth-layered structure (BLS) phase and the good ferroelectric properties of SBT films, which have been identified by x-ray diffraction spectra and P-E measurements. The remnant polarization values of SBT films on top of Pt/Ti/SiO2/Si and Pt/Ta/Ti/SiO2/Si substrates are 11.1 and 14.2 μC/cm2 at 5 V, respectively. The same phenomenon was also observed at specimens with an increased annealing temperature of 800 °C. Consistently, the SBT film with Ta adhesion layer displays a better polarization value of 16.2 μC/cm2 than that with Ti adhesion layer (12.6 μC/cm2). The fatigue tests of all samples depict the near-fatigue-free characteristics except for the specimens with Ti adhesion layer crystallized at 800 °C. It is suggested that the employment of the Ta element for the adhesion layer in the SBT process is more favorable to obtain a desirable BLS phase and to improve the ferroelectric properties.

Electrical Properties and Microstructures of Microwave Sintered PZN-Based Ceramics

In this work, Pb(Zn 1/2 Nb 2/3 )O 3 (PZN)-BaTiO 3 (BT)-Pb(Zr 0.52 Ti 0.48 )TiO 3 (PZT) ceramics were prepared by solid phase reactions via Columbite method. Relevant oxide powders were mixed and processed using microwave sintering (MS) and conventional sintering (CS) techniques. PZN-PZT-BT ceramics using partially crystallized powders exhibited similar ferroelectric characteristics in polarization-electric field measurements regardless the sintering methods. but MS samples might show more dispersion in the dielectric constant curves as a function of frequency in the weak-field dielectric properties. However, MS specimens fabricated from fully crystallized powder exhibit much better electrical properties than the CS specimens. TEM investigations of PZN-PZT-BT ceramics reveal that the MS specimens often show smaller, less-uniform grains and more complicated domain arrangements may exist. Besides, the results imply that microstructures of the specimens can be improved using microwave sintering if well-crystallized powders were adopted, and therefore enhance the electrical properties.

Electrical Properties and Microstructures of Microwave Sintered PZN-Based Ceramics

In this work, Pb(Zn 1/3 Nb 2/3 )O 3 (PZN)-BaTiO 3 (BT)-Pb(Zr 0.52 Ti 0.48 )TiO 3 (PZT) ceramics were prepared by solid phase reactions via Columbite method. Relevant oxide powders were mixed and processed using microwave sintering (MS) and conventional sintering (CS) techniques. PZN-PZT-BT ceramics using partially crystallized powders exhibited similar ferroelectric characteristics in polarization-electric field measurements regardless the sintering methods, but MS samples might show more dispersion in the dielectric constant curves as a function of frequency in the weak-field dielectric properties. However. MS specimens fabricated from fully crystallized powder exhibit much better electrical properties than the CS specimens. TEM investigations of PZN-PZT-BT ceramics reveal that the MS specimens often show smaller, less-uniform grains and more complicated domain arrangements may exist. Besides, the results imply that microstructures of the specimens can be improved using microwave sintering if well-crystallized powders were adopted, and therefore enhance the electrical properties.

Electrical Properties and Microstructures of Microwave Sintered PZN-Based Ceramics

In this work, Pb(Zn 1/3 Nb 2/3 )O 3 (PZN)-BaTiO 3 (BT)-Pb(Zr 0.52 Ti 0.48 )TiO 3 (PZT) ceramics were prepared by solid phase reactions via Columbite method. Relevant oxide powders were mixed and processed using microwave sintering (MS) and conventional sintering (CS) techniques. PZN-PZT-BT ceramics using partially crystallized powders exhibited similar ferroelectric characteristics in polarization-electric field measurements regardless the sintering methods, but MS samples might show more dispersion in the dielectric constant curves as a function of frequency in the weak-field dielectric properties. However. MS specimens fabricated from fully crystallized powder exhibit much better electrical properties than the CS specimens. TEM investigations of PZN-PZT-BT ceramics reveal that the MS specimens often show smaller, less-uniform grains and more complicated domain arrangements may exist. Besides, the results imply that microstructures of the specimens can be improved using microwave sintering if well-crystallized powders were adopted, and therefore enhance the electrical properties.

Electrical Properties and Microstructures of Microwave Sintered PZN-Based Ceramics

In this work, Pb(Zn 1/2 Nb 2/3 )O 3 (PZN)-BaTiO 3 (BT)-Pb(Zr 0.52 Ti 0.48 )TiO 3 (PZT) ceramics were prepared by solid phase reactions via Columbite method. Relevant oxide powders were mixed and processed using microwave sintering (MS) and conventional sintering (CS) techniques. PZN-PZT-BT ceramics using partially crystallized powders exhibited similar ferroelectric characteristics in polarization-electric field measurements regardless the sintering methods. but MS samples might show more dispersion in the dielectric constant curves as a function of frequency in the weak-field dielectric properties. However, MS specimens fabricated from fully crystallized powder exhibit much better electrical properties than the CS specimens. TEM investigations of PZN-PZT-BT ceramics reveal that the MS specimens often show smaller, less-uniform grains and more complicated domain arrangements may exist. Besides, the results imply that microstructures of the specimens can be improved using microwave sintering if well-crystallized powders were adopted, and therefore enhance the electrical properties.

Characterization of Ferroelectric Property of C-Axis- and Non-C-Axis-Oriented Epitaxially Grown Bi2VO5.5 Thin Films

Epitaxial Bi2VO5.5 films with c-axis- and non-c-axis-orientations were grown by metalorganic chemical vapor deposition. (001)-, (114)- and (102)-oriented Bi2VO5.5 films were epitaxialy grown on (100), (110) and (111)SrTiO3 substrates, respectively. Electrical properties of the (001)- and (114)-oriented films on (100)SrRuO3∥(100)SrTiO3 and (110)SrRuO3∥(110)SrTiO3 substrates were compared. The dielectric constant (εr) of the (001)-oriented film was smaller than that of the (114)-oriented one, suggesting that εr along the c-axis is smaller than that along other axes. Leakage current density of the (001)-oriented film was smaller than that of the (114)-oriented one. These results were in good agreement with those of the crystallographically equivalent oriented films of SrBi2Ta2O9 and Bi4Ti3O12. Ferroelectricity and domain structure were observed for both films by Polarization-Electric field measurements and scanning nonlinear dielectric microscopy, respectively. However, the large difference of remanent polarization depending on the film orientation observed for SrBi2Ta2O9 and Bi4Ti3O12 films was not observed for Bi2VO5.5 films.

Fatigue properties and microstructures of (Pb,Ca)TiO3 ceramics

Electric fatigue properties and microstructures of Ca-modified lead titanate (Pb1−xCaxTiO3) ceramics were investigated using polarization-electric field measurements and transmission electron microscopy. Specimens show an extraordinary increasing in remanent the polarization after switching up to 106 cycles for specimens with certain compositions. The coercive fields of specimens with different Ca content exhibit different behavior. The x=0.5 specimens show a decreasing in the coercive field when cyclically loaded. The x=0.4 specimen just shows a decrease and then an increase in Ec while the coercive field of the x=0.3 specimens reveals an increasing trend. Microstructural investigations indicate that when the c/a ratio is large, intersecting domain boundaries are induced under repeated application of electric field. On the other hand, when x=0.5, the number of domain boundaries does not increase significantly, suggesting that domain boundary mobility is higher for Pb0.5Ca0.5TiO3 specimens.

Ferroelectricity in sol-gel derived Ba0.8Sr0.2TiO3 thin films using a highly diluted precursor solution

Barium strontium titanate films with good ferroelectricity have been obtained by a developed sol-gel processing, using a highly dilute spin-on solution. X-ray diffraction and scanning electron microscopy investigations show that large grains with the size of 100–200 nm in the films are formed from highly dilute spin-on solutions with layer-by-layer homoepitaxy. Polarization-electric field and dielectric constant-temperature (εr−T) measurements reveal that the ferroelectricity becomes more evident as the grain size increases. The measurements for quality Ba0.8Sr0.2TiO3 ferroelectric films derived from a 0.05 M solution have shown a remnant polarization of 3.5 μC/cm2, a coercive field of 86 kV/cm, and two distinctive phase transitions.

Ferroelectric properties of Pb0.6Sr0.4TiO3 thin films on perovskite buffer layers

Pb0.6Sr0.4TiO3(PSrT) thin films were fabricated on perovskite buffer layers, La0.5Sr0.5CoO3(LSCO), La0.5Sr0.5MnO3(LSMO) and modified-SrTiO3on either the Si(100) wafer or the Pt/Ti/SiO2/Si substrates using pulsed-laser-deposition technique in the present work and ferroelectric as well as fatigue properties of the specimens were investigated. Polarization-electric field (P-E) measurements imply that PSrT films deposited upon LSCO and LSMO buffer layers exhibit different ferroelectric characteristics after repeated loading. Ferroelectric properties of PSrT films on various buffer layers are quite different and ferroelectric properties deteriorate quickly if the resistance of the buffer is high. PSrT films on oxide/Pt electrodes show ferroelectric properties with higher remanent polarization, lower coercive field and better fatigue-resistance than those of PSrT on an oxide electrode. It is easier to prepare high quality PSrT/LSMO/Pt than to fabricate PSrT/LSCO/Pt. Fatigue resistance of PSrT/LSMO/Pt is better than that of PSrT/LSCO/Pt, which can be attributed to the interfacial stress condition as well as atomic interdiffusion of the films.

Microstructural Evolution under Polarization Switching of Ferroelectric Tin-modified Lead Zirconate Titanate Ceramics

Electric fatigue properties of ferroelectric niobium-doped tin-modified lead zirconate titanate (PNZST) ceramics were investigated using polarization-electric field (P–E) measurements, and the corresponding microstructure evolution was studied employing transmission electron microscopy. The results show that domain boundaries are induced under repeated electric field application, and the microstructures become more complicated due to domain intersection. The mobility of domain boundaries degrades and the polarization of the material decreases because the intersection of domain boundaries introduces enormous strain fields and defects in the materials. A large number of dislocations and microcracks were observed in some regions when the specimens were repeatedly loaded for 106 cycles. In contrast, the remanent polarization of the ferroelectric PNZST degraded to 83% of its initial value and only half of the degraded polarization was recoverable after a refresh treatment, indicating that defects in grains play important roles in fatigue properties.

Charge Trapping Centers in Ferroelectric Ceramics

ABSTRACTElectron paramagnetic resonance (EPR), photo-thermal deflection spectroscopy (PDS), and electrical measurements have been used to characterize as-received and UV-lluminated lead lanthanum zirconate titanate (PLZT) and PZT ceramics. Following optical illumination we observe the activation of positively charged Pb+3 and negatively charged Ti+3 ions, as well as an increased broad absorption peak around 2.6 eV. The spatial distribution of the induced absorption correlates well with the location of the absorbed UV, suggesting that photo-produced carrier pairs are trapped at Ti+4 and Pb+2 producing the observed paramagnetism. The Ti+3 EPR spectra were successfully fit using the crystal field parameters derived from the PDS spectra. Preliminary results suggest that these charged paramagnetic ions can influence the electrical properties of PZT thin films. We investigated the effects of UV light and dc bias sequences by polarization-electric field (PE) measurements and find that the coercive fields are dependent on the sign of the applied bias during UV exposure. It is reasonable to expect that Pb+3 and/or Ti+3 ions act as the charge trapping sites which cause the threshold voltage shifts in the PE loop.