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Environmentally friendly Pb-free piezoelectric ceramics are essential for electronic industries and devices utilizations owing to their excellent piezoelectric properties which enable powerful sensor, transducer and actuator developments. In the present work, highly dense complex perovskite oxide ceramics with the formula of (1-x)[0.94Bi0.5Na0.5TiO3-0.06BaTiO3]-x(Ba0.7Sr0.3)TiO3 or (1-x)[0.94BNT–0.06BT]-xBST, where x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mol fraction were fabricated by a solid-state mixed oxide method. After sintering at 1125°C for 2 h, all ceramics were characterized with attention paid on their phases, microstructures, dielectric, ferroelectric, piezoelectric and strain properties as a function of BST content. The unit all size expansion i.e. higher degree of tetragonality was detected as BST content increased. All compositions exhibited single perovskite phase and uniform microstructures containing cubic-like grains with average grain size range of all ceramics was in the order of ~ 0.75–1.57 µm, depending on the amount of BST. It was interestingly found that the addition of BST enhanced the densification, sintering ability, grain size and electrical properties of BNT-BT ceramics, indicating their potential Pb-free piezoelectric candidates for future actual applications. [ABSTRACT FROM AUTHOR]

The (Bi0.5(Na0.80K0.20)0.5)1-x(Ba0.7Sr0.3)xTiO3 or (BiNK)1-x(BaS)xT (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol fraction) lead-free piezoelectric ceramics were firstly made by a conventional one step mixed-oxide method and sintered at 1125 °C for 2 h with a heating rate of 5 °C/min. All samples showed optimum relative densities of ∼97–98%. The XRD result indicated that no impurity phase was detected in all fabricated samples. SEM images indicated that all ceramics possessed irregular shaped grains. It was also found that BST added content had an effect on electrical properties of BNKT ceramics. The highest piezoelectric coefficient (d33 = 164 pC/N) with good dielectric (εr = 1577, tanδ = 0.0855) and ferroelectric properties (Pr = 11.38 µC/cm2, Ec = 19.89 kV/cm) were obtained for (BiNK)0.98(BaS)0.02T sample. [ABSTRACT FROM AUTHOR]

In the present work, highly dense complex perovskite oxide ceramics with the formula of (1-x)[Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3]-x(Ca3Co4O9) or (1-x)[BNKT-0.005LN]-xCCO, where x = 0, 0.010, 0.015, 0.020 and 0.025 mol fraction were fabricated by a solid-state mixed oxide method. After sintering at 1125 °C for 2 h, all ceramics were characterized in terms of physical, phase evolution, microstructure, dielectric, ferroelectric, and piezoelectric properties. XRD patterns of all samples indicated single phase of perovskite structure with good relative density value of ∼ 97 − 98%. The SEM image indicated that cubic-like shaped grains were observed in all samples. The average grain size was found to increase with increasing the modifier content. Optimum electrical properties (i.e. εr = 1485, tanδ = 0.0460, Pr = 13.13 µC/cm2, Ec =14.92 kV/cm and d33 = 145 pC/N) were found in the sample with x = 0.010 mol fraction. [ABSTRACT FROM AUTHOR]

It is well known that the Bi0.5(Na0.80K0.20)0.5TiO3 or BNKT ceramic possesses quite high piezoelectric coefficient (i.e., d33 ~ 151 pC/N). This research attempted to prepare (1-y)[0.995Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3]-y(Ba0.98Nd0.02)TiO3 or (1-y)[0.995BNKT-0.005LN]-yBNdT (where y = 0–0.05 mol fraction) lead- free ceramics by conventional sintering method. The optimum sintering condition was found to be 1100°C with a 2 h dwell time with a heating/cooling rate of 5°C/min. The XRD patterns of all samples showed pure perovskite phase. The optimized electrical properties were found in the sample having the composition of y = 0.03 mol fraction. Its dielectric constant was ~1980 with the dielectric loss of 0.0508 at room temperature and ~5987 with dielectric loss of 0.0540 at 268°C. The maximum Smax value of 0.25% with d*33 = 491 pm/V, and the piezoelectric coefficient of 258 pC/N were also obtained. The polarization-electric field hysteresis loops of pure and lightly-doped samples indicated a normal ferroelectric behavior. The transition to anti-ferroelectric behavior was observed for the samples with high BNdT content. This showed that the electrical properties of BNKT-LN ceramics could be tuned by small addition of BNdT with the optimum FoM values of 3.80 pm2/N. These lead-free compounds may be suitable for energy harvesting applications. [ABSTRACT FROM AUTHOR]

The effects of ZnO modification on the dielectric, ferroelectric, and electrostrictive properties of 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMNT) ceramics are systematically studied in this work. The PMNT/xZnO (with x = 0, 0.4, 2.0, 4.0, and 11.0 mol. %) ceramics of complex perovskite structure were prepared by solid state reaction and sintering process. It is found that the maximum value of the dielectric constant decreases with increasing ZnO amount up to x = 4.0 mol. %, and then significantly increases with x = 11.0 mol. %. The temperature of maximum dielectric constant tends to increase, while the diffuseness of the dielectric peak is reduced, with increasing ZnO content. The remanent polarization and the coercive field increase with increasing ZnO concentration. The induced strain and the electrostrictive coefficient reach the maximum values of 0.10% (at E = 10 kV/cm) and 12.94 × 10-16 m2/V2, respectively, with x = 2.0 mol. % ZnO. The ceramic doped with a high ZnO content (11.0 mol. %) exhibits a macroscopically polar phase with a well-developed ferroelectric hysteresis loop and butterfly-shaped bipolar piezoelectric response. This enhanced long-range polarization and the resulting properties are attributed to the effects of the partial substitution of Zn2+ for Mg2+, which favors a higher degree of polar order and a lower degree of relaxor behavior. [ABSTRACT FROM AUTHOR]

The ceramics of Bi2O3-added Ba0.85Ca0.15Zr0.1Ti0.9O3or BCZT-xBi (wherex= 0.005, 0.01, 0.02 and 0.1 mol fraction) were fabricated from sol-gel auto-combustion derived BCZT and commercial Bi2O3powders. In this study, BCZT-0.02Bi ceramic sintered at 1200°C for 2 h was found to be the optimum composition with high relative density and homogeneous microstructure. The temperature at maximum dielectric constant (Tmax) of this sample was near room temperature, rendering a high dielectric constant value (∼1653). Frequency dependence of Tmaxsuggested the relaxor behavior which was also supported by slim ferroelectric hysteresis loops. Since a relatively large breakdown voltage (> 70 kV/cm) was observed, the BCZT-0.02Bi ceramic could be a potential lead-free electrostrictive/piezoelectric material for actuator applications. [ABSTRACT FROM AUTHOR]

In this work, the relationships between phase development and the properties of a new relaxor based ferroelectric (1-x)Pb(Mg1/3Nb2/3)0.9Ti0.1O3-xBi0.5(Na0.74K0.26)0.5TiO3ceramics (whenx= 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 mole fraction) was studied. The pseudo-cubic structure was observed in the ceramics withx≤ 0.7 mole fraction. The rhombohedral and tetragonal phases were found to coexist whenxincreased to 0.9, which transformed into the single tetragonal phase whenxincreased to 1.0. The dielectric constant measured at room temperature decreased with increasingx. The remnant polarization and piezoelectric constant of the ceramics significantly increased whenxincreased to 0.9 and 1.0. [ABSTRACT FROM AUTHOR]

Phase formation, microstructures, dielectric, and ferroelectric properties of ZnO-modified Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMNT/xZnO, where x = 0, 0.4, 2.0, 4.0, and 11.0 mol%) ceramics were studied. A coexistence of rhombohedral and tetragonal ferroelectric phases was observed at room temperature in all samples. The ceramics with the relative densities of 93%-95% were prepared. The modification by ZnO led to an increase in grain sizes of PMNT ceramics. The maximum dielectric constant of the pure PMNT ceramic was increased with x = 0.4-4.0 mol% ZnO doping, with the highest value being observed in the 2.0 mol% sample. Both the temperature at which the transition between rhombohedral and tetragonal ferroelectric phases took place (TR-T) and the Curie temperature of the ceramics tended to increase with increasing x. The ferroelectric properties were enhanced with increased remanent polarization and P(E) loop squareness in the compositions with x = 0.4-4.0 mol%. However, the ferroelectric properties were attenuated with x = 11.0 mol%. [ABSTRACT FROM AUTHOR]