Piezoelectric Thermal Stability Research Articles

Influence of MnO2 on the ferroelectric properties, energy storage efficiency and piezoelectric properties of high-temperature Bi3TaTiO9 ceramics

High-temperature BLSFs Bi3TiTaO9 integrated with MnO2, exhibits excellent piezoelectric thermal stability and energy storage efficiency, making it a promising candidate for future wide-temperature pulse power applications.

Improved dielectric and piezoelectric thermal stability by chemical homogenization in CuO-modified 0.75BiFeO3-0.25BaTiO3 piezoceramics

0.75BiFeO3-0.25BaTiO3 lead-free ceramics have been considered promising candidates for high-temperature piezoelectric applications. However, their dielectric and piezoelectric properties severely degrade with increasing temperature. In this work, improved dielectric and piezoelectric thermal stability was obtained in CuO-modified 0.75BiFeO3-0.25BaTiO3 ceramics. CuO addition increases the volume fraction of the rhombohedral phase in the 0.75BiFeO3- 0.25BaTiO3 ceramics and makes the chemical heterogeneity disappear. The dielectric and piezoelectric anomalies are eliminated near 300 °C and return with CuO additions, and the temperature degradations of the dielectric constant and piezoelectric coefficient of 0.75BiFeO3-0.25BaTiO3 ceramics with 0.008 mol CuO in the range from 25 to 400 °C decrease by 85% and 60%, respectively. Furthermore, the depoling temperature and piezoelectric coefficient of 0.75BiFeO3-0.25BaTiO3 ceramics with 0.008 mol CuO are 570 °C and 131 pC/N, respectively. These results indicate that CuO addition is an effective approach to improve both the dielectric and piezoelectric thermal stability of 0.75BiFeO3-0.25BaTiO3 ceramics.

High temperature piezoelectric accelerometer fabricated by 0.75BiFeO3–0.25BaTiO3 ceramics with operating temperature over 450 °C

Owing to the high Curie temperature and good piezoelectric thermal stability, BiFeO3–BaTiO3 ceramics show great potentials for high-temperature piezoelectric sensor applications. In this paper, a compression-mode piezoelectric sensor was fabricated by the lead-free and high-temperature 0.75BiFeO3–0.25BaTiO3–MnO2 (BFBT25–Mn) ceramic and its sensitivity was characterized from room temperature to 550 °C over a frequency range of 200–1000 Hz. The output charge of the BFBT25–Mn piezoelectric sensor is independent of the measuring frequency at different temperatures. The maximum working temperature of the BFBT25–Mn piezoelectric sensor is 450 °C, about 250, 150, and 100 °C higher than those of these piezoelectric sensors fabricated by PZT-5A, BSPT64–Mn, and BSPT66–Mn ceramics, respectively. The temperature sensitivity coefficient from room temperature to 350 °C of the BFBT25–Mn piezoelectric sensor is 30% of that for the BSPT66–Mn sensor. Furthermore, the sensitivity of the BFBT25–Mn piezoelectric sensor is stable with the dwelling time at 400 °C. These results indicate that the BFBT25–Mn ceramic is a strong competitor for high temperature sensing applications.

Thermal stability of piezoelectricity in polylactide polymers and related piezoelectric minimotor application

Piezoelectric polymers have been widely used in a variety of applications, including tactile sensors, energy harvesting, polymer actuators, and biological devices. In this investigation, we fabricated the PLLA (poly(L-lactic Acid)-based bimorph structures for piezoelectric motor applications. First, a strain measurement setup was established to measure the strain of the PLLA and PDLA film at different temperatures. The effective piezoelectric constants d14 calculated for the PLLA and PDLA films were 10.2 pC/N and 9.4 pC/N, respectively. Furthermore, the PLLA films showed a strong thermostability of piezoelectricity at 130°C. The PLLA bimorph minimotor showed the maximum load of 1.2 g and the maximum torque of 0.019 cN·m. The minimotors were capable of rotating a plastic hemisphere container in the clockwise and counterclockwise directions at 65 V voltage. Due to the light weight, low driving voltage, and thermal stability, the PLLA/PDLA motors show a great promise in future Braille display, robots, and mini-digital camera applications.

Microscopic origin of the enhanced piezoelectric thermal stability in acceptor doped lead-free Ba(Ti0.8Zr0.2)O3-50(Ba0.7Ca0.3)TiO3 ceramic

Acceptor doping is effective in enhancing thermal stability in piezoceramics, while the reason underlying is still unclear and awaits explanation. In this work, through doping acceptor Mn in lead-free Ba(Ti 0.8 Zr 0.2 )O 3 -50(Ba 0.7 Ca 0.3 )TiO 3 ceramic, our results show that doping Mn achieves higher depolarization temperature, even higher than Curie temperature ( T C ) and simultaneously a better piezoelectric thermal stability. Through microscopic and macroscopic analysis, the enhancement can be explained by the clamping effect induced by acceptor doping, which is carefully demonstrated by symmetry-conforming short-range ordering tendency theory. Thus, this work reveals the mechanism for enhanced depolarization temperature and piezoelectric thermal stability due to acceptor doping and will help developing new thermal stable lead-free piezoceramics applicable in a wider temperature range.

Correlation between grain size and electrical properties of high‐temperature lead‐free 0.70BiFeO3‐0.30BaTiO3 ceramics

Abstract0.70BiFeO3‐0.30BaTiO3 (0.70BF‐0.30BT) ceramics have been widely concerned because of their potential applications for high‐temperature piezoelectric devices. In this work, a series of dense 0.70BF‐0.30BT ceramics with average grain size variation from 0.55 to 6.0 μm were prepared. XRD results indicate that 0.70BF‐0.30BT ceramics show the coexistence of rhombohedral and pseudo‐cubic phases and the volume fraction of the rhombohedral phase increase with the grain size. The dielectric, ferroelectric and piezoelectric properties increase with the grain size initially from 0.55 to 5.0 μm and then decrease slightly. Values of d33, Pr, and εr, of 0.70BF‐0.30BT ceramics with the grain size of 5.0 μm are 185 pC/N, 21.2 μC/cm2, and 638, respectively, about five times higher than those ceramics with fine‐grain of 0.55 μm. Of particular importance is that 0.70BF‐0.30BT ceramics with large grain sizes possess better piezoelectric thermal stability due to the much stabler poled domain state with the rising temperature. The detailed structural studies indicate that the enhanced electric properties are owing to the significantly improved domain motion and the increased lattice distortion. This clarifying the relationship between electrical properties and grain size offers a novel way of improving the performances of piezoceramics.

Investigation on the Correlation between Piezoelectricity and Its Thermal Behavior with Depolarization Temperature and Antiferroelectric Order in Niobium‐Doped (Na0.41K0.09Bi0.5)TiO3: A Lead‐Free Piezoelectric

A correlation between piezoelectric response and its thermal stability with the depolarization temperature and antiferroelectric order in (Na0.41K0.09Bi0.5)(1−x/2)(Ti1−xNbx)O3 (x = 0.00–0.0150) ceramic is investigated. A reasonable increase in the piezoelectric response (20–25%) is observed in a limited composition range (0.0050 ≤ x ≤ 0.010). The piezoelectric thermal stability for the lower niobium concentrations (x < 0.010) is found to be reasonably better than many archetypal lead‐free piezoelectrics. However, a significant thermal instability is observed for the higher niobium content (x ≥ 0.010). The observed thermal instability is attributed to the monotonic decrease in the depolarization temperature with the emergence of antiferroelectric ordering in the vicinity of the ferroelectric‐relaxor crossover region. The increase in the piezoelectric response in the aforementioned composition range is associated with the competition among the ferroelectric domain wall movement and the antiferroelectric order. The outcome of the current study reveals that (Na0.41K0.09Bi0.5)(1−x/2)(Ti1−xNbx)O3 with x = 0.005 is a useful lead‐free piezoelectric with consistent thermal response.

Role of oxygen vacancy defects in piezoelectric thermal stability characteristics of Mn-doped (K,Na,Li)NbO3 piezoceramics

Piezoelectric thermal stability characteristics of (K,Na,Li)NbO3 ceramics were investigated with a particular focus on the role of oxygen vacancy defects, by excluding the lattice distortion or microstructural effects with the help of a low level of Mn doping (less than 1.0 mol%). Benefiting from the reduction of intrinsic oxygen vacancy defects, controlled Mn doping (0.25 mol%) could achieve excellent ferroelectric/piezoelectric activity and superior thermal aging resistance. Beyond this doping level, however, the defect dipoles combined with extrinsic oxygen vacancies, although advantageous to the hardening effect, deteriorated the piezoelectric thermal stability and aging resistance including room-temperature properties. The thermal dissociation and migration of oxygen-vacancy-associated defect dipoles were considered mainly responsible for negating the ability to restore the initial poled domain state with defect-dipole-induced polarization. Results demonstrated the importance of keeping the intrinsic and extrinsic oxygen vacancy levels as low as possible for lead-free (K,Na)NbO3 systems with more thermally stable domain structure.

Effects of Nano-Sized In2O3 on Sintering Behavior and Electrical Properties of 0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 Ceramics

0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 ceramics were synthesized by conventional solid-phase method using nano-sized In2O3. All the sintered 0.28PIN-0.40PMN-0.32PT ceramics have pure perovskite structure with composition locating at rhombohedral side around the morphotropic phase boundary (MPB) region. The 0.28PIN-0.40PMN-0.32PT ceramics belong to displacive driving ferroelectrics with apparent diffused phase transition characteristic. Although the rhombohedral-tetragonal ferroelectric phase transition temperature (TR-T) increases only to ∼120 °C due to the solid solution of Pb(In1/2Nb1/2) (PIN), the 0.28PIN-0.40PMN-0.32PT ceramics present high piezoelectric thermal stability till around the Curie temperature (Tm), which extremely widens the working temperature range and makes the 0.28PIN-0.40PMN-0.32PT ceramics suitable for high-temperature piezoelectric applications.

Understanding the mechanism of thermal-stable high-performance piezoelectricity

Lead zirconate titanate (PZT) ceramics have been widely used because of their large piezoelectric response and good temperature-stability in the vicinity of morphotropic phase boundary (MPB). However, the understanding on the mechanism of temperature-stable piezoelectricity in PZT is still blur and thus needs to explore properly since the urgently-needed Pb-free systems designed by the same MPB method commonly show poor temperature stability. In this paper, we investigate the property-microstructure relationship for the thermal-stable piezoelectricity through comparative studies of the phase diagram, in-situ piezoelectricity and microstructure evolution in both Pb-based and Pb-free systems. Our results show that the piezoelectric thermal-stability is closely related to the verticality of MPB and the doping elements. Tilted MPB shows worse thermal-stability as compared with that of the vertical MPB. While acceptor doped commercial PZTs show better thermal-stability when compared with that of the donor doped PZT. Moreover, our in-situ TEM reveals that it is the thermal-stable fine microstructure (i.e., no degeneration) that corresponds to the thermal-stable high-performance piezoelectricity. Our work provides an in-depth understanding of the relationship between the phase diagram, microstructure and thermal-stable piezoelectricity, which shall benefit the designing of new lead-free temperature-stable piezoelectric materials.

Large Piezoelectric Stability and Low Polarization Fatigue in 6Pb(Sc1/2Nb1/2)O3-70Pb(Mg1/3Nb2/3)O3-24PbTiO3 Crystals

The electrical properties and polarization fatigue of [001]-oriented 6Pb(Sc1/2Nb1/2)O3-70Pb(Mg1/3Nb2/3)O3-24PbTiO3 (6PSN-70PMN-24PT) crystals were investigated. Compared with binary Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals, the ternary 6PSN-70PMN-24PT crystal showed a higher rhombohedral → tetragonal transition temperature (TR-T = 120°C) and a larger coercive field (Ec = 4 kV/cm). It was found that the piezoelectric constant (d33 ≈ 1200 pC/N) and electromechanical coupling coefficient (kt ≈ 61%) were weakly dependent on the thermal annealing temperature (Ta), maintaining over 90% of the original value at Ta < 120°C, indicating excellent piezoelectric thermal stability. Electric fatigue measurements showed that the ternary 6PSN-70PMN-24PT crystal exhibited slight fatigue characteristics below 105 bipolar cycles, while the binary PMN-PT crystal exhibited sudden polarization degradation when the cycle numbers were above 102 cycles. The improved fatigue stability for 6PSN-70PMN-24PT crystals was attributed to the large coercive field. The physical mechanisms of the enhanced coercive field and high transition temperature were discussed based on repulsive energy and polar domains.

Low-temperature-sintered Bi0.5Na0.5TiO3-based lead-free ferroelectric ceramics with good piezoelectric properties

Li2CO3 has been used as a sintering aid for fabricating lead-free ferroelectric ceramic 0.93(Bi0.5Na0.5TiO3)-0.07BaTiO3. A small amount (0.5wt%) of it can effectively lower the sintering temperature of the ceramic from 1200°C to 980°C. Unlike other low temperature-sintered ferroelectric ceramics, the ceramic retains its good dielectric and piezoelectric properties, giving a high dielectric constant (1570), low dielectric loss (4.8%) and large piezoelectric coefficient (180 pC/N). The “depolarization” temperature is also increased to 100°C and the thermal stability of piezoelectricity is improved. Our results reveal that oxygen vacancies generated from the diffusion of the sintering aid into the lattices are crucial for realizing the low temperature sintering. Owing to the low sintering temperature and good dielectric and piezoelectric properties, the ceramics, especially of multilayered structure, should have great potential for practical applications.

Investigation of phase structure, microstructure, and electrical properties of LaAlO3-modified alkali niobate lead-free perovskite

LaAlO3 as an effective additive for modification of KNN system has never been systemically discussed before. Here, (0.96−x)K0.48Na0.52NbO3–0.04Bi0.5Na0.5ZrO3–xLaAlO3 (KNN–BNZ–xLA) ceramics have been synthesized by traditional solid-state sintering with a special emphasis on the influences of LaAlO3 components on the crystallographic structure, microstructure, and electrical properties. XRD and Rietveld refinements were performed to explore the effects of LaAlO3 on the phase evolution and the crystallographic structure, respectively, which revealed a coexistence of tetragonal and orthogonal phases. And through the results of the temperature-dependent dielectric constant (e r−T), we found the phase boundary shifted to low temperature slowly with the increase of LaAlO3 components. As a resut, the samples with x = 0.004 demomstrated the excellent properties of d 33 ~ 354 pC/N, k p ~ 46%, T C ~ 325 °C, P r ~ 21.8 μC/cm2, tan δ ~ 3.9%, together with a high strain value as high as 0.18% at 50 kV cm−1, which are originated to the contributions of the crystallographic structure transition and dense microstructure. Additionally, it is worth noting that such a good thermal stability of piezoelectricity (e.g., d 33 ≥ 303 pC/N, T ≤ 300 °C) was also observed by thermal depoling method and temperature-dependent P–E hysteresis loops. Not only is this work itself scientifically fascinating but it also renders these materials appealing for practical applications as a candidate for lead-based ones.

Titanium deficiency in tetragonal-structured (Ba,Ca)(Zr,Ti)O 3 piezoelectric ceramics

Abstract Effect of titanium deficiency on the structure and electrical properties of lead-free (Ba0.838Ca0.162)(Ti0.908-xZr0.092)O3 (0.46BZT-0.54BCTx, x = 0.000, 0.0004, 0.0008, 0.0012, 0.0016, 0.0020) compositions was investigated. The Ti-deficient compositions exhibited typically tetragonal-structured characteristics confirmed by XRD and Raman spectra regardless of trace amount of Ti deficiency. Ti-deficiency could result in double doping mechanism, namely soft characteristic for low Ti deficiency and hard characteristic for high Ti deficiency. Thermal stability of piezoelectricity could be effectively improved by Ti deficiency compared to pure 0.46BZT-0.54BCT, but inferior to Mn-doping composition. This defect engineering can be an effective and promising way to tailor the thermal stability of piezoelectric materials suitable for high temperature applications.

Piezoelectric Thermal Stability of (K x Na 1-x )NbO 3 Based Ceramics

Abstract Lead-free piezoelectric ceramics (K x Na 1- x ) 1- y Li y Nb 0.80 Ta 0.20 O 3 ( x =0.40∼0.60; y =0.03, 0.035, 0.04) were prepared by a conventional solid-state reaction method, and the thermal stability of piezoelectric properties was investigated. Results show that samples in the researched compositional range have high piezoelectric constant of d 33 =250 pC/N and k p =50%. In the thermal aging test up to the Curie temperature of approximately 325 o C, d 33 and k p of the ceramics remain almost unchanged although there is polymorphic phase transition (PPT) near room temperature. Moreover, the ceramics present the very good piezoelectric temperature stability and k p shows a weak temperature dependence over a wide measured temperature range from −50 °C to 120 °C. The excellent thermal stability was discussed from the aspect of temperature range of phase coexistence

Composition dependence of phase structure and electrical properties of (1−y)Bi1−x Nd x FeO3−y BiScO3 ceramics

In this work, we have studied a new lead-free ceramic of (1 - y )Bi1 - x Nd x FeO3- y BiScO3 (0.05 £ x £ 0.15 and 0.05 £ y £ 0.15) prepared by a conventional solid-state method, and the influences of Nd and Sc content on their phase structure and electrical properties were investigated in detail. The ceramics with 0.05 £ x £ 0.10 and 0.05 £ y £ 0.15 belong to an R3c phase, and the rhombohedral-like and orthorhombic multiphase coexistence is established in the composition range of 0.125 £ x £ 0.15 and y =0. The electrical properties of the ceramics can be enhanced by modifying x and y values. The highest piezoelectric coefficient ( d 33~51 pC/N) is obtained in the ceramics with x =0.075 and y =0.125, which is superior to that of a pure BiFeO3 ceramic. In addition, a lowest dielectric loss (tan δ ~0.095%, f =100 kHz) is shown in the ceramics with x =0.15 and y =0 due to the involvement of low defect concentrations, and the improved thermal stability of piezoelectricity at 20–600oC is possessed in the ceramics. We believe that the ceramics can play a meaningful role in the high-temperature lead-free piezoelectric applications.

Significantly improved piezoelectric thermal stability of cellular polypropylene films by high pressure fluorination and post-treatments

Cellular polypropylene (PP) films were fluorinated under a high pressure of 13 bar of the F2/N2 mixture and were post-treated by nitrous oxide and isothermal crystallization. The fluorinated and post-treated PP films after being expanded and corona charged exhibit a significantly improved piezoelectric thermal stability. After annealing at 70 °C for 151 h or at 90 °C for 224 h, the piezoelectric d33 value of the fluorinated and post-treated piezoelectric sample still retains 58% or 45% of its initial d33 value, while the corresponding value of the virgin piezoelectric sample has decreased to 29% or 15% of the initial value. Chemical composition analysis of the cross section of the fluorinated and post-treated film by energy-dispersive x-ray spectroscopy indicates that the internal layers have been fluorinated, in spite of a lower degree of fluorination compared with the fluorinated surface layer. Short-circuit and open-circuit TSD current measurements reveal that the fluorinated internal layers, like the fluorinated surface layer, also have very deep charge traps, although there probably is a difference in density of the deep traps between them. The deeply trapped charge on the internal layers of the fluorinated and post-treated piezoelectric sample is responsible for its significantly improved piezoelectric thermal stability.

Piezoelectric properties and thermal stability of (Na0.53K0.47−xAgx)Nb1−xSbxO3 ceramics

AbstractMany (K1−xNax)NbO3 (KNN)‐based ceramics with high piezoelectric performance exhibit undesirable strong temperature dependence due to the orthorhombic–tetragonal polymorphic phase transition near room temperature. In order to improve the temperature stability of the ceramics, many additives have been added into the KNN‐based ceramics to shift TO–T down to below room temperature. Contrary to the previous approach (Na0.53K0.47−xAgx)Nb1−xSbxO3 (NKANS) ceramics with TO–T well above room temperature have been prepared by a conventional solid‐state reaction method. The density and the electrical properties are effectively improved by the addition of AgSbO3, and optimum piezoelectric properties are found in the ceramics with 0.05 ≤ x ≤ 0.07, with maximum kp ∼ 0.46 for NKANS5 and maximum d33 ∼ 199 pC/N for NKANS7. More importantly, kp remains virtually almost unchanged up to the TO–T temperature (≥100 °C), indicating that the NKANS ceramics exhibit a much improved piezoelectric thermal stability. The analyses suggest that both the high TO–T value and diffuse orthorhombic–tetragonal phase transition should be responsible for the good temperature stability.

Thermal Properties and Phase Transition Behavior of KNN-AN Piezoelectric Ceramics

Piezoelectric thermal stability is often a critical issue for many piezoelectric materials in practical applications. Lead-free piezoelectric ceramics, (1−x)K0.5Na0.5NbO3– xAgNbO3 (KNN-AN, with x = 0–0.35) have been synthesized by a conventional solid state sintering method. The temperature dependence of the dielectric, ferroelectric and piezoelectric properties of lead-free piezoelectric ceramics was investigated. The piezoelectric properties exhibit a very good thermal stability up to high temperature, which is a significant improvement from other KNN-based piezoceramics.

Characterization and piezoelectric thermal stability of PIN–PMN–PT ternary ceramics near the morphotropic phase boundary

The phase structure and piezo/dielectric properties of xPb(In 1/2Nb 1/2)O 3– yPb(Mg 1/3Nb 2/3)O 3– zPbTiO 3 (PIN–PMN–PT x/ y/ z) ternary ceramics with morphotropic phase boundary (MPB) composition were investigated. It was found that Curie temperatures of choosing composition changed from 165 °C to 293 °C and the piezoelectric properties are almost the same at room temperature in PIN–PMN–PT system near MPB. The piezoelectric coefficient d 33 and electromechanical coupling factor k p are higher than 440 pC/N and 60%, respectively. Temperautre and dc bias dependence of piezoelectric response for PIN–PMN–PT ceramics were measured. The usage temperature range was found to be improved, compared with PMN–PT single crystal near MPB.