Planar Coupling Factor Research Articles

Hard piezoelectric properties of lead‐free BiFeO3–BaTiO3 ceramics

AbstractHard piezoelectric properties are investigated in lead‐free BiFeO3–BaTiO3 (BF–BT) ceramics. Rhombohedral (R) phase ceramics of (1 – x)BF–xBT (x = 0.20–0.30) were prepared using a conventional solid‐state reaction and water‐quenching process. The R structure is observed in x = 0.20–0.275, and the R and tetragonal phases coexist at x = 0.30. The piezoelectric charge sensor coefficient (d33) and electromechanical planar coupling factor (kp) increase with increasing BT content, whereas the mechanical quality factor (Qm) decreases. The x = 0.20 ceramic shows the best hard piezoelectric properties: the highest Qm = 403 and the highest TC = 607°C. In contrast, x = 0.30 ceramic shows soft piezoelectric properties: d33 = 301 pC/N and kp = 0.33 with TC = 510°C. These results show that the BF–BT system in R‐phase‐rich region has good hard piezoelectric properties for transducer applications.

Dielectric Spectroscopy Studies and Modelling of Piezoelectric Properties of Multiferroic Ceramics

Compounds and solid solutions of bismuth ferrite (BiFeO3)—barium titanate (BaTiO3) system are of great scientific and engineering interest as multiferroic and potential high-temperature lead-free piezoelectric materials. In the present paper, the results of research on the synthesis and characterisation of 0.67Bi1.02FeO3–0.33BaTiO3 (67BFBT) ceramics in terms of crystal structure and dielectric and piezoelectric properties are reported. It was found that the produced 67BFBT ceramics were characterised by a tetragonal crystal structure described by the P4mm space group, an average crystallite size <D> ≈ 80 nm, and an average strain <ε> = 0.01%. Broad-band dielectric spectroscopy (BBDS) was employed to characterise the dielectric response of polycrystalline ceramics. The frequency range from ν = 10−1 Hz to ν = 105 Hz was used to characterise the influence of the electric field strength on dielectric response of the ceramic sample at room temperature. The dielectric spectra were checked for consistency with the Kramers–Kronig test, and the high quality of the measurements were confirmed. The electric equivalent circuit method was used to fit the dielectric spectra within the frequency range that corresponded to the occurrence of the resonant spectra of the radial mode for thin disk sample, i.e., from ν = 105 Hz to ν = 107 Hz and the temperature range from T = −20 °C to T = 50 °C. The electric equivalent circuit [RsCPE1([L1R1C1]C0)] was used, and good fitting quality was reached. The relevant calculations were performed, and it was found that the piezoelectric charge coefficient exhibited a value of d31 = 35 pC/N and the planar coupling factor was kp = 31% at room temperature. Analysis of impedance spectra performed in terms of circumferential magnetic field made it possible to establish an influence of magnetic field on piezoelectric parameters of 67BFBT multiferroic ceramics. Additionally, the “magnetic” tunability of the modulus of the complex dielectric permittivity makes 67BFBT a sensing material with vast potential.

Piezoelectric Response and Cycling Fatigue Resistance of Low-Temperature Sintered PZT-Based Ceramics

The preparation of low-cost multilayer piezoelectric devices requires using cheap internal electrodes between the dielectric layers. A general strategy is to reduce the sintering temperature Ts of the ceramic layer by sintering aids which can form a liquid phase. Here, 0.2 wt% Li2CO3 was added as a sintering aid to tailor the sinterability and piezoelectricity of the commercial PZT ceramics. As verified from experiments, the piezoelectric ceramics could be densified at a sintering temperature above 940 °C, suitable for co-firing with the cheap internal electrode. The optimized sintering temperature of 980 °C can be confirmed for the 0.2 wt% Li2CO3-modified PZT ceramics due to its high piezoelectric coefficient d33 ~ 701 pC/N, planar coupling factor kp ~ 66.7%, and a low mechanical quality factor Qm ~ 71 with a transition temperature of Tc ~ 226 °C, presenting the characteristics of typical soft piezoelectric ceramics. Moreover, both the potential piezoelectric strain ~0.13% under 20 kV/cm and the good cycling fatigue characteristic (>104 cycles) of the studied piezo compositions indicates strong competitiveness in the field of multilayer piezoelectric devices.

The electrical properties of low-temperature sintered 0.07Pb(Sb1/2Nb1/2)O3-0.93Pb(ZrxTi1−x)O3 multilayer piezoceramic actuator

0.07Pb(Sb1/2Nb1/2)O3-0.93Pb(ZrxTi1−x)O3 (PSbN-PZT) piezoceramics were fabricated at a low firing temperature of 920 °C using the LiBiO2, CuO and ZnO (LBCZ) sintering aids. The material samples exhibited excellent properties, including a converse piezoelectric coefficient d33* of ~558 pm/V, a relative dielectric permittivity εT33/ε0 of ~1725, a planar coupling factor kp of ~0.6 and a high Curie temperature Tc of ~308 °C, thus demonstrating the material suitability for use as a low-cost multilayer actuator. PSbN-PZT piezoceramic multilayer actuators with Ag/Pd internal electrodes were fabricated by tape casting method cofired at 920 °C. A large displacement of 1.45 μm was achieved in a single PSbN-PZT multilayer actuator (thickness = 2.0 mm) at the driving voltage of 125 V, while the displacement decreased ~27% under the mechanical stress of ~32 MPa. Good temperature stability was also exhibited in PSbN-PZT multilayer actuator, which was better than that of commercial PZT-5H ceramic. These results indicated that low-temperature fired PSbN-PZT multilayer actuator is a promising candidate device for commercial piezoactuator applications.

Structure, dielectric and piezoelectric properties of Pb[(Zr0.45,Ti0.5)(Mn0.5,Sb0.5)0.05]O3 ceramics

This study describes structure, dielectric and piezoelectric properties of Pb[(Zr0.45,Ti0.5)(Mn0.5,Sb0.5)0.05]O3 (PZT-PMS) ceramics prepared by conventional mixed-oxide route and sintered at up to 1180?C. The prepared ceramics was characterized by X-ray diffraction and scanning electron microscopy. The piezoelectric constants, dielectric constant, Young?s modulus and electromechanical factors were measured in broad temperature range. The results showed that the PZT-PMS ceramics is composed of tetragonal and rhombohedral phases and has the average grain size of about 1 ?m. The Pb[(Zr0.45,Ti0.5)(Mn0.5,Sb0.5)0.05]O3 ceramics has excellent dielectric and piezoelectric properties for wide practical applications. Thus, planar coupling factor of 0.70, poled dielectric constant of 8215, the Curie temperature of 345?C and dielectric loss of 6% were attained in the PZT-PMS ceramics sintered at 1180?C.

High piezoelectric properties of Sm2O3 doped Ba0·85Ca0·15Ti0·90Zr0·10O3 ceramics

This paper discussed the properties of Sm2O3 doped Ba0·85Ca0·15Ti0·90Zr0·10O3 (BCTZ–xSm) ceramics, which were prepared under the high temperature solid state reaction method. Piezoelectric and dielectric properties were observed from these BCZT–xSm ceramics later. Results revealed that the addition of Sm2O3 improved the piezoelectric property of BCZT ceramics significantly while affecting the Curie temperature (Tc) negatively. The BCZT ceramic with x = 0·2 mol.-% displayed an excellent electrical behaviour with excellent piezoelectric coefficient (d33 = 554 pC N− 1), planar coupling factor (KP = 53%), dielectric constant () and dielectric loss (tan δ = 1·8%) when sintered at 1450°C.

Ultrasonic transducers based on undoped lead-free (K0.5Na0.5)NbO3 ceramics

Lead zirconate titanate (PZT) ceramics are the dominant piezoelectric elements for non-destructive evaluation (NDE) and ultrasonic transducers devices. However, the presence of lead content may impose the scientific community to develop lead-free ceramics, concerning human health and environmental safety. During the past ten years, many contributions have highlighted the potential properties of complex compositions like LiNbO3, LiTaO3 and LiSbO3 in the lead-free (K0.5Na0.5)NbO3 KNN system. In this context, for the first time, the practical applications and the effectiveness of simply undoped (K0.5Na0.5)NbO3 (KNN) ceramics are investigated. KNN powder is prepared by conventional solid state mixed oxide route. Ceramics of this material are prepared using conventional sintering (CS) and spark plasma sintering (SPS). Thickness coupling factor kt of 44–46%, planar coupling factor kp of 29–45%, relative permittivity at constant strain ε33,rS of 125–243 and acoustic impedance Z of 23–30MRay are obtained for these two kinds of undoped KNN ceramics. Both ceramics are used to build single-element ultrasonic transducers. Relative bandwidth of 49–78% and insertion loss of −27 and −51dB are obtained for SPS and CS transducers, respectively. These results are suitable for use in non-destructive evaluation. The effectiveness of undoped KNN is evaluated using the KLM model, and compared to standard PZT based probe. Finally, chemical aging test of undoped KNN has demonstrated its stability in water.

Structure and electrical properties of (1 − x)(Na0.5Bi0.5)0.94Ba0.06TiO3–xSmAlO3 lead-free piezoelectric ceramics

(1 − x)(Na0.5Bi0.5)0.94Ba0.06TiO3–xSmAlO3 [(1 − x)BNBT6–xSA] lead-free piezoelectric ceramics were synthesized by conventional solid-state method. Effects of composition on the micro-structure and electrical properties of (1 − x)BNBT6–xSA ceramics were investigated. X-ray diffraction data shows that (1 − x)BNBT6–xSA ceramics form the pure perovskite phases, and the ceramics have the morphotropic phase boundary when x ≤ 0.0100. At room temperature, the electrical properties of the BNBT6 ceramics have been improved with the addition of appropriate SA. At room temperature, (1 − x)BNBT6–xBA ceramics at x = 0.0100 has the highest remnant polarization (P r = 47 μC/cm2), the highest piezoelectric coefficient (d 33 = 179 pC/N), the highest planar coupling factor (k p = 0.296), the higher dielectric constant (ɛ r = 1154) and higher mechanical quality factor (Q m = 131).

Photoluminescence and Temperature Dependent Electrical Properties of Er‐Doped 0.94Bi0.5Na0.5TiO3‐0.06BaTiO3 Ceramics

Er‐doped 0.94Bi0.5Na0.5TiO3‐0.06BaTiO3 (BNT‐6BT: xEr, x is the molar ratio of Er3+ doping) lead‐free piezoceramics with x = 0–0.02 were prepared and their multifunctional properties have been comprehensively investigated. Our results show that Er‐doping has significant effects on morphology of grain, photoluminescence, dielectric, and ferroelectric properties of the ceramics. At room temperature, the green (550 nm) and red (670 nm) emissions are enhanced by Er‐doping, reaching the strongest emission intensity when x = 0.0075. The complex and composition‐dependent effects of electric poling on photoluminescence also have been measured. As for electrical properties, on the one hand, Er‐doping tends to flatten the dielectric constant‐temperature (εr‐T) curves, leading to temperature‐insensitive dielectric constant in a wide temperature range (50°C–300°C). On the other hand, Er‐doping significantly decreases the ferroelectric‐relaxor transition temperature (TF–R) and depolarization temperature (Td), with the TF–R decreasing from 76°C to 42°C for x = 0–0.02. As a result, significant composition‐dependent electrical features were found in ferroelectric and piezoelectric properties at room temperature. In general, piezoelectric and ferroelectric properties tend to become weaker, as confirmed by the composition‐dependent piezoelectric coefficient (d33), planar coupling factor (kp), and the shape of polarization‐electric field (P–E), current‐electric field (J–E), bipolar/unipolar strain‐electric field (S–E) curves. Furthermore, to understand the relationship between the TF–R/Td and the electrical properties, the composition of x = 0.0075 has been intensively studied. Our results indicate that the BNT‐6BT: xEr with appropriate Er‐doping may be a promising multifunctional material with integrated photoluminescence and electrical properties for practical applications.

Influence of Calcium Concentration on the Structural and Electrical Properties of PZT Ceramic

Lead zirconate titanate, with Zr/Ti ratio of 53/47 was prepared by the polymeric precursor method. The powders were doped with 0, 0.2, 0.4 end 0.6 mol% of Ca2+and characterized by XRD. The percentages of tetragonal and rhombohedral phases were calculated through Rietveld refinement. A systematic study of the effect of dopant on the ferroelectric and piezoelectric properties of PZT was carried out. The remanent polarization, planar coupling factor and piezoelectric charge constant, increase with dopant concentration.

Characterization of the High‐Temperature Ferroelectric (100−x−y)BiScO3–(x)Bi(Zr0.5Zn0.5)O3–(y)PbTiO3 Perovskite Ternary Solid Solution

Ternary compositions based on Bi(B′B″)O3–PbTiO3‐type compounds have been investigated for high‐temperature piezoelectric applications. Compositions in the ternary were chosen to be near the binary morphotropic phase boundary (MPB) composition of BiScO3–PbTiO3 (BS–PT). Ternary compositions in (100−x−y)BiScO3–(x)Bi(Zr0.5Zn0.5)O3–(y)PbTiO3 [(100−x−y)BS–xBZZ–yPT] have been investigated with x ≤ 7.5. For compositions with x > 10, the Curie temperature (TC) decreased below 400°C. Dielectric, piezoelectric, and electromechanical properties were characterized as a function of temperature, frequency, and electric field. Small additions of BZZ were shown to increase the electromechanical properties with only a small loss in TC. The electromechanical properties were temperature stable up to the depoling temperature. The most promising composition exhibited a TC of 430°C, piezoelectric coefficient (d33) of 520 pC/N, and a planar coupling factor (kp) of 0.45 that remained unchanged up to depoling temperature at 385°C.

Accelerated processing route for KNN based piezoceramics

It is known that the properties of potassium–sodium–niobate (KNN, K0·46Na0·54NbO3) are sensitive to processing and that the most successful way of stabilising and improving material performance is proper doping of KNN. However, this leads to more complex material systems, whose synthesis is very time consuming to assess by conventional processing techniques. On the other hand, known high throughput routes impose a serious interference with conventional processing, resulting in significant differences of the findings, or inaccessibility of certain parameters. In this paper, an accelerated processing route is introduced and compared with conventional mixed oxide processing regarding the density, large signal piezoelectric charge constant, permittivity, loss tangent planar coupling factor, specific resistivity and microstructure. By means of three differently doped KNN based compositions, it is shown that the accelerated processing route yields reproducible results, which are equal or even superior to conventional techniques, while the processing time and the batch costs are significantly reduced.

Effects of different synthesizing processes on the dielectric and piezoelectric properties of 0.65(K0.5Bi0.5TiO3)–0.35BaTiO3 ceramics

Abstract In this study, 0.65(K 0.5 Bi 0.5 )TiO 3 –0.35BaTiO 3 (KBT–BT3) ceramics were synthesized using two different methods: a conventional calcination process (CC-process) and a two-step calcination process that combined hydrothermal and CC processes (HT–CC-process). The effects of the differently synthesizing processes on the physical and dielectric properties of the KBT–BT3 ceramics were recorded and analyzed. Two secondary phases, BaBi4Ti4O15 and K4Ti3O8, were observed in the XRD patterns of the CC-process KBT–BT3 ceramics. The formations of BaBi 4 Ti 4 O 15 and K 4 Ti 3 O 8 compounds made the CC-process KBT–BT3 ceramics having poor dielectric properties. When the HT–CC-process was used and the KBT–BT3 ceramics were sintered at 1050–1100 °C, the secondary phases were not observed and only the (K 0.5 Bi 0.5 , Ba)TiO 3 phase was observed in the XRD patterns. As same sintering temperature was used, the dielectric constants of the HT–CC-process KBT–BT3 ceramics were higher than those of the CC-process KBT–BT3 ceramics. Electromechanical coupling factors, such as the planar coupling factor ( k p ), thickness coupling factor ( k t ), and longitudinal coupling factor ( k 33 ), were also used to explain the effect of the different synthesizing processes on the properties of the KBT–BT3 ceramics.

Structure and electrical properties of (Bi0.5Na0.5)0.94Ba0.06TiO3–Bi0.5(Na0.82K0.18)0.5TiO3–BiAlO3 lead free piezoelectric ceramics

0.09(Bi0.5Na0.5)0.94Ba0.06TiO3–(0.01 − x) Bi0.5(Na0.82K0.18)0.5TiO3–x BiAlO3 (BNBKT–xBA) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction processes. Structure, ferroelectric and piezoelectric properties of BNBKT–xBA ceramics were investigated. X-ray diffraction data shows that BNBKT–xBA ceramics form the pure perovskite phases and the ceramics have the morphotropic phase boundary when x ≤ 0.030. At room temperature, the BNBKT–xBA ceramics at x = 0.030 have better electrical properties, the piezoelectric constant d33 and planar coupling factor kp of BNBKT–xBA ceramics reaches peak values at x = 0.030: d33 = 217 pC N−1, kp = 0.308. The remnant polarization Pr, mechanical quality factor Qm and relative dielectric constant ɛr of BNBKT–xBA ceramics at x = 0.030 attains 33.8 μC cm−2, 133 and 928 (100 KHz), respectively. As BA content increase, the depolarization temperature Td shift toward lower temperature, and Td of BNBKT–xBA ceramics with x = 0.030 decreased to 55 °C.

Structure and electrical properties of (1 − x) (Na0.5Bi0.5)0.94Ba0.06TiO3–x BiAlO3 lead-free piezoelectric ceramics

(1−x) (Na0.5Bi0.5)0.94Ba0.06TiO3–x BiAlO3 ((1−x) BNBT6–x BA) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. Effects of BiAlO3 (BA) on the structure and electrical properties of (Na0.5Bi0.5)0.94Ba0.06TiO3 (BNBT6) ceramics were investigated. X-ray diffraction (XRD) data shows that (1−x) BNBT6–x BA ceramics form the pure perovskite phases, and the ceramics have the morphotropic phase boundary (MPB) when x<0.0500. At room temperature, the electrical properties of the BNBT6 ceramics have been improved with the addition of appropriate BA. At room temperature, (1−x) BNBT6–x BA ceramics at x=0.0225 have the highest remnant polarization (Pr=42.5μC/cm2), the highest piezoelectric coefficient (d33=204pC/N), the highest planar coupling factor (kp=0.3292), the highest dielectric constant (ɛr=1687) and higher mechanical quality factor (Qm=112).

Effects of SmCoO3 on the microstructure and piezoelectric properties of (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics

(Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 (abbreviated to BNBT6) ceramics doped with 0–0.6 mol.% SmCoO 3 were synthesized by the conventional solid-state reaction method, and the effect of SmCoO 3 addition on the dielectric and piezoelectric properties was investigated. X-ray diffraction (XRD) patterns show that SmCoO 3 diffuses into the lattice of the BNBT6 ceramics to form a solid solution with a pure perovskite structure. SEM images indicate that the addition of SmCoO 3 caused a remarkably promoted grain growth. Our results reveal that both the piezoelectric and electromechanical properties of BNBT6 ceramics could be greatly improved by certain amount of SmCoO 3 substitutions. At room temperature, the BNBT6 ceramics doped with 0.4 mol.% SmCoO 3 exhibit the optimum properties with high piezoelectric constant ( d 33 =144 pC/N), high planar coupling factor ( k p =29.1%), and high mechanical quality factor ( Q m =219).

Poling Field Dependence of Longitudinal and Transverse Wave Velocities, Young's Modulus, and Poisson's Ratio in Piezoelectric Ceramics

The longitudinal and transverse wave velocities in lead zirconate titanate (PZT), lead titanate, and lead-free ceramics vs DC poling fields were measured using an ultrasonic precision thickness gauge with high-frequency pulse oscillation to evaluate elastic constants, such as Young's modulus and Poisson's ratio. With the enhancement of domain alignment with the increase in poling field, the longitudinal wave velocity increased and the transverse wave velocity decreased independently of the ceramic composition. It was found that there was an important factor for obtaining a high piezoelectricity regarding Young's modulus and Poisson's ratio, that is, the low Young's modulus and high Poisson's ratio in the cases of PZT, alkali bismuth titanate, and alkali bismuth barium titanate with morphotropic phase boundaries (MPBs), and alkali niobate without MPBs. Furthermore, the increase in planar coupling factor corresponds to the increase in Poisson's ratio at all compositions including lead-containing and lead-free ceramic compositions. It was possible to divide the ceramics on the basis of longitudinal and transverse wave velocities into three groups, namely, PZT and lead titanate modified by 2.5 mol % lanthanum, alkali bismuth titanate and lead titanate modified by 10 mol % lanthanum, and alkali niobate.

Dielectric, pyroelectric and piezoelectric properties in the (1 − x)(0.1BaTiO3–0.9NaNbO3)–xLiNbO3 system

New lead free piezoceramics with the given compositions (1 − x)(0.1BaTiO3–0.9NaNbO3)–xLiNbO3(0.01 ≤ x ≤ 0.125) were prepared by solid–state reaction technique. XRD patterns revealed a single perovskite-structured phase only for 0.01 ≤ x < 0.05. The dielectric, pyroelectric and piezoelectric responses were investigated for compositions with x = 0.01 and 0.02. For both compositions, ɛ’r exhibited a sharp peak with no frequency dependence (classical ferroelectrics). Losses displayed a strong dispersion at low frequencies in the paraelectric phase which was attributed to Li ionic conductivity in these compositions. The spontaneous polarization was found to be 35 and ≈22 μC cm−2 for x = 0.01 and 0.02 respectively. The transverse piezoelectric coefficient d31 measured for x = 0.01 reached value of 37 pC/N at room temperature while the planar coupling factor was about 0.23.

Structure and electrical properties of the Ho2O3 doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 lead-free piezoelectric ceramics

Ho2O3 (0–0.7 wt%)-doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 (BNKT18) lead-free piezoelectric ceramics were synthesized by a conventional solid-state reaction method. The effects of Ho2O3 on the microstructure and electrical properties were investigated. X-ray diffraction data shows that Ho2O3 in an amount of 0.1–0.7 wt% can diffuse into the lattice of the BNKT18 ceramics and form the pure perovskite phase. Scanning electron microscope (SEM) images indicate that the grain sizes of BNKT18 ceramics decrease with the increase of Ho2O3 content; in addition, the modified ceramics have the clear grain boundary and a uniformly distributed grain size. At room temperature, the electrical properties of the BNKT18 ceramics have been improved with the addition of Ho2O3, and the BNKT18 ceramics doped with 0.3wt.% Ho2O3 have the highest piezoelectric constant (d33 = 137 pC/N), the highest remnant polarization (Pr = 26.9 μC/cm2), the higher relative dielectric constant (er = 980) and lower dissipation factor (tanδ = 0.046) at a frequency of 10 kHz. The BNKT18 ceramics doped with 0.1 wt% Ho2O3 have the highest planar coupling factor (kp = 0.2426).

Structure and electrical properties of (1 − x) (Bi0.5 (Na0.82K0.18)0.5) TiO3–x BiAlO3 lead-free piezoelectric ceramics

(1−x) (Bi0.5 (Na0.82K0.18)0.5) TiO3–x BiAlO3 [(1−x) BNKT18–x BA] lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction method. Structure and electrical properties of (1−x) BNKT18–x BA ceramics were investigated. X-ray diffraction (XRD) data shows that (1−x) BNKT18–x BA ceramics form the pure perovskite phases. Scanning electron microscope (SEM) images indicate that the grain sizes of (Bi0.5 (Na0.82K0.18)0.5) TiO3 (BNKT18) ceramics decrease with the addition of BiAlO3 (BA). At room temperature, the ferroelectric and piezoelectric properties of the BNKT18 ceramics have been improved by the addition of appropriate BA. At room temperature, the remnant polarization Pr, piezoelectric coefficient d33, planar coupling factor kp and relative dielectric constant εr of (1−x) BNKT18–x BA ceramics at x=0.0075 all reach maximum values: Pr=39.3μC/cm2, d33=171pC/N, kp=0.3128 and εr=1583.