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(1 − x)[(KNaLi)(NbTaSb)O]- xBiNaNbO (KNLNTS- xBNN) lead-free piezoelectric ceramics have been prepared using a conventional solid-state reaction method and the effects of BNN on their phase structure, microstructure, and electrical properties systematically studied. X-ray diffraction analysis suggested that BNN substitution into KNLNTS induced coexistence of orthorhombic-tetragonal mixed phase and thus improved the ferroelectric and piezoelectric properties. The surface morphologies indicated that different amounts of BNN had two different effects on grain growth. Good electrical properties ( d = 256 pC N, T = 354.27°C, k = 43.43%, P = 26.85 μC cm, E = 24.47 kV cm) were simultaneously obtained at x = 0.0025, suggesting that our research could benefit development of (K,Na)NbO-based ceramics and widen their application range. [ABSTRACT FROM AUTHOR]

The effects of M 2 O 5 (M = Nb, Ta, Sb) addition on the phase transition and electrical properties of 0.94Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 (BNBT6) lead-free ceramics were studied. Results showed that M substitution into BNBT6 induced a phase transition from coexistence of ferroelectric tetragonal and rhombohedral to a relaxor pseudocubic with a significant disruption of the long-range ferroelectric order. Accordingly, large strain response of 0.42–0.43% with fatigue-free behavior, which is due to a reversible field-induced ergodic relaxor-to-ferroelectric phase transformation, was obtained at 0.5 mol% M content. Furthermore, as the compositions ( x ≥ 0.06) lied deep in the pseudocubic region of the phase diagram, a high, purely electrostrictive effect with large electrostrictive coefficient Q 33 of 0.020–0.024 m 4 /C 2 was achieved. More interestingly, the obtained BNBT6-based electrostrictors showed good resistance to both long-term electric cycling (up to 10 6 cycles) and thermal influence (20–160 °C), rendering them suitable for high-precision positioning devices and other actuators. [ABSTRACT FROM AUTHOR]

In this study, new lead-free luminescent electrostrictive materials have been fabricated by introducing trivalent RE 3 + (RE = Sm, Pr and Eu) as the activator into 0.93(Bi 0·5 Na 0.5 )TiO 3 –0.07BaTiO 3 (BNBT7) ceramics. A high, purely electrostrictive effect with exceptionally good temperature-independent and fatigue-free behavior was obtained in RE-modified BNBT7 ceramics. These materials are also attractive for their strong photoluminescence with bright reddish-orange emission (RE = Sm) or red emission (RE = Pr, Eu) upon blue or green light excitation. These results suggest that this kind of materials has potential application as a multifunctional device by integrating its excellent luminescence and electrostrictive properties. [ABSTRACT FROM AUTHOR]

Lead - free (Bi 1/2 Na 1/2 ) 0.935+ x Ba 0.065 Ti 1− x (Pr 1/2 Nb 1/2 ) x O 3 (BNBT– x PN) piezoelectric ceramics were prepared by the conventional solid-state reaction method and the crystal structure and electrical properties were systematically investigated. X-ray diffraction patterns revealed that the (Pr 1/2 Nb 1/2 ) 4+ completely diffused in the BNBT lattice in the studied composition range. An appropriate amount of (Pr 1/2 Nb 1/2 ) 4+ additive enhanced the dielectric, ferroelectric, and piezoelectric properties of BNBT ceramics. The P r and d 33 increased from 29.1 μC/cm 2 and 121 pC/N of pure BNT to 32.8 μC /cm 2 and 221 pC/N of modified ceramics with x =0.0050, respectively. Furthermore, electric field-induced strain was enhanced to its maximum value ( S max =0.34%) with normalized strain ( d 33 * = S max / E max =567 pm/V) at an applied electric field of 60 kV/cm for x =0.0075. These findings have great potential for actuator and multifunctional device applications, which may also open up a range of new applications. [ABSTRACT FROM AUTHOR]

In this work, we studied aging and fatigue behaviors of 1.0 mol%Cu-modified (Na0.5K0.5)NbO3 lead-free ceramics with double-loop-like characteristic, and found an interesting result of electric field cycling induced large electrostrain in the aged samples. After the 'aging' treatment, the hysteresis loop 'closes' totally and constricts completely at zero electric field, accompanying with a large nonlinear electrostrain of about 0.26%. More interestingly, the electrostrain in the aged sample is sensitive to the field cycling, which is pushed to a higher level of 0.47% approaching that of some Pb-based antiferroelectric materials. A microscopic model of the domain switching-related electrostrain effect is proposed to explain the field cycling induced large electrostrain in the aged samples. It can be identified due to the weakening of intrinsic restoring force for reversing the switched domains, induced by the point defects (defect dipoles) migration aligning along field direction during cycling, evident by the gradually 'opened' hysteresis loop with cycling. [ABSTRACT FROM AUTHOR]

HoO doped (KNa)LiNbSbO (KNLNS) lead-free piezoelectric ceramics were prepared by normal sintering to construct rhombohedral-orthorhombic polymorphic phase boundary. An orthorhombic and rhombohedral phase boundary is formed in the ceramics around x = 0.6-0.8, indicating that the doping of HoO is helpful to stabilize the low temperature rhombohedral structure. The surface and interior of the x ≤ 0.6 samples exhibit tetragonal and orthorhombic structures, respectively, which demonstrate that phase transitions can be induced by the alkali metal oxides volatilization during sintering. Anomalous broad dielectric relaxation is observed in the ε- T curves near T when x ≥ 0.8. Abnormal grain growth occurs when small amount of HoO is added but the grain size decreases at high amount of HoO. The optimum electrical properties of d = 252 pC/N, k = 39.67 %, ε = 930.4, and Q = 59.5 are obtained at x = 0.6. These results show that the KNLNS ceramic with 0.6 wt% HoO is a promising lead-free piezoelectric material. [ABSTRACT FROM AUTHOR]

The MTiO (M = Ca, Sr, Ba, BiNa, BiK and BiLi)-modified (KNa)LiNbO lead-free piezoelectric ceramics were prepared using normal sintering for improving the temperature stability and fatigue resistance of (KNa)NbO-based ceramics. Results showed that MTiO substitution into (KNa)LiNbO shifts the polymorphic phase transition below room temperature. The dominant crystal phase changes from coexistence of orthorhombic and tetragonal phase to tetragonal phase with the MTiO addtion. Accordingly, the temperature stability and fatigue resistance of the modified ceramics were significantly improved. It was found that 1.0 mol% MTiO (M = Ca)-modified (KNa)LiNbO ceramics exhibited nearly temperature-independent properties (25-160 °C), fatigue-free behavior (up to 10 cycles) and good piezoelectric properties ( d = 245 pm/V), indicating these materials promising for actuator and transducers applications. [ABSTRACT FROM AUTHOR]

In this study, we designed a series of compositions deep in pseudocubic region based on ternary (1− x)[(1− y)(BiNa)TiO- y(BiK)TiO]- x(KNa)NbO (BNKT100 y-100 xKNN) system for electrostrictive applications. Results show that the KNN substitution into BNKT100 y induces a significant disruption of the ferroelectric order, and tends to enhance the electrostrictive properties of the ceramics. A high, purely electrostrictive effect with large electrostrictive coefficient Q of 0.025 m/C and good thermostability comparable with that of traditional Pb-based electrostrictors is obtained for BNKT100 y- xKNN ( y = 0.20, x = 0.16) ceramics, which lies deep in pseudocubic region along the MPB compositions of the ternary system. Temperature-dependent structural analysis suggests that the good electrostrictive properties insensitive to temperature can be ascribed to the stable relaxor pseudocubic phase over a wide temperature range. Furthermore, it is found that the electrostrictive coefficient Q exhibits only small degradation within 2 % at the field amplitude of 80 kV/cm up to 10 switching cycles. The large and purely electrostrictive effect with the exceptionally good fatigue resistance and thermostability makes this material a great potential to be applied to the environmental-friendly solid-state actuators. [ABSTRACT FROM AUTHOR]

The 0.935Bi 1/2 Na 1/2 TiO 3 –0.065BaTiO 3 –100 x Bi 2 FeCrO 6 ( x =0–0.013) (BNT–BT–100 x BFCO) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method and the effect of BFCO addition on the microstructure and electrical properties of the ceramics was investigated. All the samples have a relative density higher than 97% of their theoretical values. X-ray diffraction (XRD) patterns show that all compositions have a pure perovskite structure and BFCO effectively diffused into the BNT–BT lattice during sintering to form a solid solution. SEM images indicate that the grain size of BNT–BT ceramics firstly increases and then decreases with the increase of BFCO content, and all the modified ceramics have a clear grain boundary and a uniformly distributed grain size. Appropriate BFCO doping into BNT–BT ceramics induce the enhancement of piezoelectric and ferroelectric properties. Improved P r =42.3 μC/cm 2 , low E c of 28.7 kV/cm, and high d 33 =214 pC/N, k p =33% were observed at x =0.007. These results indicate that the modified BNT–BT ceramics might be promising lead-free piezoelectric candidates for practical applications. [ABSTRACT FROM AUTHOR]

Lead-free ceramics (1− x − y ) Bi 1/2 Na 1/2 TiO 3 – x BaTiO 3 – y Y 2 NiMnO 6 (BNT–BT–YNMO– x / y ) were prepared by conventional solid-state reaction method and their structure and electrical properties were systematically investigated. The X-ray diffraction patterns showed that all the samples exhibit a pure perovskite phase with rhombohedral structure. All the modified ceramics with a clear grain boundary and uniformly distributed grain size were observed in SEM images. Either increasing x or y content can enhance ferroelectric and piezoelectric properties. The optimum electrical properties can be obtained at x =0.065 and y =0.002, which are as follows: P r =38.05 μC/cm 2 , E c =21.42 kV/cm, d 33 =219 pC/N and k p =29.5%. The results indicate that the BNT–BT–YNMO– x / y ceramics are promising lead-free piezoelectric candidates for practical applications. [ABSTRACT FROM AUTHOR]

The 0.935Bi 1/2 Na 1/2 TiO 3 –0.065BaTiO 3 – x mol⋅Bi 2 NiMnO 6 ( x = 0–0.008) (abbreviated as BNT–BT6.5– x BNMO) lead-free piezoelectric ceramics were fabricated by conventional solid-state reaction method and the effects of BNMO addition on microstructure and electrical properties of the ceramics were investigated. Results show that all samples have formed dense structures with a large relative density > 95%. X-ray diffraction (XRD) patterns show all compositions had a pure perovskite structure, suggesting BNMO effectively diffused into the BNT–BT6.5 lattice to form a solid solution. SEM images indicate that BNMO modified ceramics have a clear grain boundary and a uniformly distributed grain size. The measurements of electrical properties reveal that the electrical properties of BNT–BT– x BNMO ceramics have been greatly improved by certain amount of BNMO substitutions. At room temperature, the BNT–BT– x BNMO ceramics with appropriated BNMO exhibited optimum ferroelectric and piezoelectric properties with a relatively high remnant polarization P r of 31 μC/cm 2 , high planar electromechanical coefficient k p of 31% and large piezoelectric constant d 33 of 229 pC/N, respectively. These results indicate that the modified BNT–BT6.5 ceramics are promising lead-free piezoelectric candidates for practical applications. [ABSTRACT FROM AUTHOR]

(1 − x)(NaBi)BaTiO- xSmAlO [(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 = 47 μC/cm), the highest piezoelectric coefficient ( d = 179 pC/N), the highest planar coupling factor ( k = 0.296), the higher dielectric constant ( ɛ = 1154) and higher mechanical quality factor ( Q = 131). [ABSTRACT FROM AUTHOR]

Abstract: (Na0.52K0.45Li0.03)1−3x La x (Nb0.88Sb0.09Ta0.03)O3 (NKLL x NST) lead-free ceramics were prepared by normal sintering and their dielectric and piezoelectric properties were investigated. The X-ray methods indicate that the NKLL x NST ceramics with x≤0.003 present a pure perovskite phase at room temperature. The bulk density of NKLL x NST ceramics increases with proper amount of La2O3 contents, and reaches its highest value of 4.544g/cm3 with the addition of 0.3mol% La2O3. At x=0.003, remnant polarization P r, piezoelectric constant d 33 and planar mode electromechanical coupling factor k p of NKLL x NST ceramics reach the highest values of 37.80μC/cm2, 346pC/N and 40%, respectively, exhibiting excellent “soft” piezoelectric characteristics, demonstrating a tremendous potential of the compositions studied for device applications. [Copyright &y& Elsevier]

The non-stoichiometric (KNa)(NbTa)O ( x = 0, ±0.005, ±0.010) [KN(NT)] lead-free piezoelectric ceramics were prepared by normal sintering. The samples were characterized by X-ray diffraction and scanning electron microscopy. All the KN(NT) ceramics possess orthorhombic perovskite structure. The grain growth of the ceramics is inhibited and the relative density is improved with increasing x. 0.5 mol% (NT) excess KN(NT) ceramic which sintered at 1,120 °C has the highest piezoelectric performances among with other samples. Meanwhile, the (NT) excess ceramics have better time stability than the (NT) deficient ones. These results show that the KN(NT) ceramic with x = 0.005 is a promising lead-free piezoelectric material. [ABSTRACT FROM AUTHOR]

Highlights: [•] Proper addition of SA enhances mechanical quality factor of the KNLNS ceramics. [•] The doping of SA broadens the sintering temperature range of the ceramics. [•] The high d 33 and Q m mean that the x =0.005 sample is suitable for high frequency applications. [ABSTRACT FROM AUTHOR]

Abstract: Lead-free (Ba0.9Ca0.1)(Ti1−x Sn x )O3 (BCTS) (x=0.02–0.1) ceramics were fabricated using conventional solid state reaction method. The effects of Sn substitution on structure and electrical properties of the BCTS ceramics were researched. At room temperature, a polymorphic phase transition (PPT) from tetragonal phase to rhombohedral phase is identified from XRD patterns with increasing Sn content. High piezoelectric coefficient of d 33=405pC/N and planar mode electromechanical coupling factor of k p =43.2% are obtained for the sample at x=0.06. The ceramic for x=0.06 also shows uniform microstructure that contributes to the excellent electrical properties. These results indicate that this BCTS system with optimal composition is a promising lead-free piezoelectric material. [Copyright &y& Elsevier]

Abstract: Er2O3 (0–0.8wt.%)-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 Er2O3 on the microstructure and electrical properties were investigated. X-ray diffraction (XRD) data shows that Er2O3 in an amount of 0.2–0.8wt.% 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 Er2O3 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 Er2O3, and the BNKT18 ceramics doped with 0.6wt.% Er2O3 have the highest piezoelectric constant (d 33 =138pC/N), the highest planar coupling factor (k p =0.2382), the highest remnant polarization (P r =25.2μC/cm2), the higher relative dielectric constant (ε r =936) and lower dissipation factor (tanδ =0.047) at a frequency of 10kHz. Moreover, the T m and T d of the samples increase with the addition of Er2O3. [Copyright &y& Elsevier]

Abstract: Lead-free (Ba1−x Ca x )(Ti0.95Zr0.05)O3 (x = 0.05–0.40) (BCZT) ceramics were prepared by solid-state reaction technique. XRD results show that the samples in the composition range of 0.05 ≤ x ≤ 0.25 exhibit pure perovskite structures and undergo a polymorphic phase transitions from orthorhombic to tetragonal phase around room temperature. The biphasic structures are detected at x ≥ 0.30 and the dielectric peaks become broad and dielectric constants decrease with increasing Ca content. Ca replacement at Ba site leads to diffuseness, whereas Ca occupancy at Ti site leads to decrease of the T c. [Copyright &y& Elsevier]

Abstract: Lead-free (Ba1−x Ca x )(Ti0.9Zr0.1)O3 (x=0.12–0.18) (BCZT) ceramics were prepared successfully using a solid-state reaction technique. The polymorphic phase transitions (PPT) from rhombohedral to orthorhombic phase around room temperature were identified in the composition range 0.14

Abstract: Lead-free (Ba1− x Ca x )(Ti0.98Zr0.02)O3 (x =0–0.04) ceramics were prepared successfully using a solid-state reaction technique. The polymorphic phase transitions (PPT) from orthorhombic to tetragonal phase around room temperature were identified in the composition range of 0< x <0.03. High piezoelectric coefficient of d 33 =375pC/N and planar electromechanical coupling factor of k p =44.1% were obtained for the samples at x =0.01. With the increase of Ca content, the orthorhombic–tetragonal phase transitions shifted towards room temperature, while relative high Curie temperature (T C) was still maintained about 115°C. [Copyright &y& Elsevier]

• The effects of In 2 O 3 -doped on KNN ceramics were studied for the first time. • Enhanced piezoelectric and ferroelectric properties were obtained. • The addition of In 2 O 3 improved the fatigue resistance and temperature stability. In this paper, (1- x)K 0.5 Na 0.5 NbO 3 - x mol% In 2 O 3 (abbreviated as KNN- x In) lead-free piezoelectric ceramics were prepared using conventional solid sintering method. The effects of In 2 O 3 on the phase structure, microstructure, domain evolution, electrical properties, fatigue behavior and thermal stability of KNN ceramic matrix were systematically studied. XRD results show that all the ceramics possess the orthorhombic phase with domain architectures presented in the PFM. The addition of In 2 O 3 improved the fatigue resistance owing to the enhanced density. The temperature stability of the 1.0 mol% In 2 O 3 doped sample was significantly improved. It was found that the KNN ceramics with 1.0 mol% In 2 O 3 addition exhibited good electrical properties (d 33 * = 179 pm/V, d 33 = 103 pC/N, T C = 388 °C, P r = 31.52 μC/cm2, ε r = 327, tan δ = 3.28%). The results suggested that this material should be an attractive lead-free material for piezoelectric applications. [ABSTRACT FROM AUTHOR]

(K 0.44 Na 0.52 Li 0.04 )(Nb 0.86 Ta 0.1 Sb 0.04 )O 3 − x wt%Sc 2 O 3 (abbreviated as KNLNTS- x Sc) ( x = 0.0, 0.3, 0.6 and 0.9) lead-free ceramics were prepared by conventional solid-state sintering method and phase transition characteristic as well as its effects on their electrical properties were investigated systematically. The orthorhombic-tetragonal (O-T) coexistence phase boundary ( x > 0.3) can be driven via the modification of Sc 2 O 3 , which has been confirmed by XRD. The appropriate Sc content benefitted the dramatic improvement in the properties. A high strain of 0.13% at the electric-field of 30 kV/cm (corresponding to a large signal d 33 ∗ of 448 pm/V) and a relatively large d 33 value of ∼289 pC/N, along with the enhanced properties ( P r = 28.3 µC/cm 2 , E C = 16.3 kV/cm) with the maximum density, were simultaneously achieved in the same sample with x = 0.6. These results provide a better method to obtain high-performance potassium-sodium-niobate materials. [ABSTRACT FROM AUTHOR]

Lead–free piezoelectric ceramics (Bi 0.5 Na 0.5 ) 0.935 Ba 0.065 Ti 1– x (Mn 0.5 Sb 0.5 ) x O 3 (BNBT6.5– x MS, x =0.005, 0.010, 0.015, 0.020) were prepared by conventional solid state reaction sintering technique. All ceramics present a pure perovskite phase structure, indicating that (Mn, Sb) has completely diffused into the BNBT6.5 lattice in the studied components. The addition of (Mn, Sb) disrupted the ferroelectric long–range order and promoted the electric field induced strain response. At x =0.015, a large electric field–induced unipolar strain of 0.48% (at an applied electric field of 80 kV/cm) with normalized strain d 33 * ( S max / E max ) of 602 pm/V are achieved. Temperature dependent measurements of both polarization and strain from room temperature to 120 °C were also studied, and the results suggest that the origin of the large strain is due to a reversible field–induced non–polar relaxor phase to polar ferroelectric phase transformation. [ABSTRACT FROM AUTHOR]

0.948(K 0.5 Na 0.5 )NbO 3 –0.052LiSbO 3 – x MgTiO 3 ( x =0, 0.005 and 0.010) (abbreviated as KNLNS– x MT) lead-free piezoelectric ceramics were prepared by normal sintering. The effect of MT addition on KNLNS ceramics was investigated through dielectric, ferroelectric and electric field-induced strain characterizations. The grain size decreased slightly after the addition of MT, and more uniform grains were obtained. Impedance measurements made over a wide range of temperatures (425–525 °C) showed the presence of both bulk and grain boundary effects in the materials. The activation energies E a were 0.483 and 0.507 eV for KNLNS and KNLNS–0.005MT ceramics respectively, indicating that the conduction process was due to oxygen vacancies in the higher temperature region. The P r and unipolar strain of the MT modified ceramics exhibited lower temperature sensibility than KNLNS ceramics in the temperature range 30–120 °C. Meanwhile, the MT doped samples showed less degradation in both switchable polarization and unipolar strain after 10 6 switching cycles than those of KNLNS. It is expected that the KNLNS– x MT ceramics is promising candidate for lead-free piezoceramics and could be used in practical applications. [ABSTRACT FROM AUTHOR]

Lead–free piezoelectric ceramics (1− x )(Bi 1/2 Na 1/2 ) 0.935 Ba 0.065 TiO 3 − x CaYAlO 4 (BNBT6.5− x CYAO) were prepared using a conventional solid sintering technique. The addition of CYAO destroyed the ferroelectric long–range order with the shift of the ferroelectric–relaxor transition temperature T F–R down to room temperature and induced the appearance of ergodic relaxor phase. Thus, it leads to a giant field–induced strain with a peak value of 0.44% at x = 0.012. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics (Bi 0.5 Na 0.5 ) 0.935 Ba 0.065 Ti 1− x (Fe 0.5 Sb 0.5 ) x O 3 (BNBT6.5– x FS, x =0.005, 0.010, 0.015, 0.020) were prepared by a conventional solid sintering technique. The effects of B-site doping of (Fe, Sb) on the phase structure, microstructure, dielectric, ferroelectric, and piezoelectric properties of BNBT6.5 ceramics were systematically investigated. Results showed that (Fe, Sb) can completely diffuse in the BNBT6.5 lattice in the all studied components. The addition of (Fe, Sb) destroyed the ferroelectric long-range order, and thus promoted the electric field induced strain response. The maximum electric field-induced strain ( S max =0.37%) with normalized strain ( d 33 *= S max / E max =454 pm/V) at an applied electric field of 80 kV/cm was obtained at x =0.015. Temperature dependent measurements of both polarization and strain from room temperature to 120 °C suggested that the origin of the large strain is due to a reversible field-induced ergodic relaxor to ferroelectric phase transformation. [ABSTRACT FROM AUTHOR]

Lead-free 0.99[(1− x )(Bi 0.5 Na 0.5 )TiO 3 - x (Bi 0.5 K 0.5 )TiO 3 ]–0.01Ta piezoelectric ceramics were prepared by a conventional solid-state reaction process. The ferroelectric properties, and strain behaviors were characterized. Increase of the (Bi 0.5 K 0.5 )TiO 3 content induces a phase transition from coexistence of ferroelectric tetragonal and rhombohedral to a relaxor pseudocubic phase. Accordingly, the ferroelectric order is disrupted significantly with the increase of (Bi 0.5 K 0.5 )TiO 3 content and the destabilization of the ferroelectric order is accompanied by an enhancement of the unipolar strain, which peaks at a value of 0.35% (corresponding to a large signal d 33 of 438 pm/V) in samples with 20 mol% (Bi 0.5 K 0.5 )TiO 3 content. Temperature dependent measurements of both polarization and strain from room temperature to 120 °C suggested that the origin of the large strain is due to a reversible field-induced nonpolar pseudocubic-to-polar ferroelectric phase transformation. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics, (1− x )SrBi 2 Nb 2 O 9 − x BiFeO 3 [(1− x )SBN− x BFO] ( x =0.0, 0.03, 0.05, 0.07, 0.10) were prepared by a conventional solid-state reaction method. The crystal structure, microstructure and electrical properties were systematically investigated. All compositions formed layered perovskite structure without any detectable secondary phases. Plate-like morphology of the grains which is characteristic for layer-structure Aurivillius compounds was clearly observed. The excellent electrical properties (e.g., d 33 ~19 pC/N, 2 P r ~18.8 μC/cm 2 ) and a high Curie temperature (e.g., T c ~449 °C) were simultaneously obtained in the ceramics with x =0.05. Additionally, thermal annealing studies indicated that the BFO modified SBN ceramics system possessed stable piezoelectric properties, demonstrating that the modified SBN-based ceramics are the promising candidates for high-temperature applications. [ABSTRACT FROM AUTHOR]

The structure, field-induced strain, polarization and dielectric response of lead-free La 2 CoMnO 6 -modified 0.935Bi 1/2 Na 1/2 TiO 3 –0.065BaTiO 3 (BNT–BT6.5– x LCMO, with x =0–0.020) ceramics were investigated. X-ray diffraction (XRD) patterns show that all compositions have a pure perovskite structure and LCMO effectively diffused into the BNT–BT6.5 lattice during sintering to form a solid solution. Around critical composition ( x =0.005) at a driving field of 70 kV/cm, large unipolar strain of 0.22% ( S max / E max =328 pm/V) and high piezoelectric constant of 211 pC/N are obtained at room temperature. The coercive field ( E c =18.6 kV/cm) drop down greatly, whereas the remnant polarization ( P r =28.8 μC/cm 2 ) decreases only a little at this critical composition. These results indicate that BNT–BT6.5– x LCMO ceramics can be considered as promising candidate materials for lead-free piezoelectric practical applications. [ABSTRACT FROM AUTHOR]

In this study, a new lead-free luminescent electrostrictive material has been obtained by introducing trivalent Er 3+ as the activator into 0.92(Bi 0.5 Na 0.5 )TiO 3 –0.08(Ba 0.90 Ca 0.10 )(Ti 0.92 Sn 0.08 )O 3 (BNT–0.08BCST). A high, purely electrostrictive effect (the electrostrictive coefficient Q 33 reaches up to 0.028 m 4 /C 2 ) with exceptionally good fatigue resistance (up to 10 6 cycles) and thermostability (25–140 °C) is obtained in 0.2 mol%Er-modified BNT–0.08BCST ceramics. Besides the excellent electrostrictive properties, Er 3+ -modified BNT–0.08BCST samples exhibit a strong green-red upconversion emission, and the emission intensities are strongly dependent on the doping concentration, which reaches the optimal value as the doping concentration is 0.4 mol%. These results suggest that this kind of material may have potential application as a multifunctional device by integrating its excellent upconversion luminescence and electrostrictive properties. [ABSTRACT FROM AUTHOR]

SrBi 1.94- x Er 0.06 Yb x Nb 2 O 9 (x = 0.000, 0.002, 0.004 and 0.006, noted as SBEN- x Yb) composites were prepared using traditional solid-phase sintering technology. The influences of (Er, Yb)3+ co-doping on the electrical and luminous properties as well as energy band structure of SrBi 2 Nb 2 O 9 (SBN) ceramics were systematically investigated. The outstanding comprehensive characteristics with low dielectric loss (tan δ ~ 0.073%), high remnant polarization (2 P r ~ 10.73 μC/cm2), large piezoelectric responses (d 33 ~ 15 pC/N) and excellent upconversion photoluminescence (UC-PL) are simultaneously observed by Yb doping with a concentration of x = 0.004. The UC-PL spectrum excited by 980 nm laser shows double bands at 533 nm and 554 nm in the green region, and single band at 672 nm in the red region. A density functional theory (DFT) calculation was performed to reveal the physical origin of electrical conductivity and UC-PL. It is seen that the band gap consistently decreases, while the contribution from f state of (Er, Yb)3+ is intensified with increasing Yb3+, elaborating the variations of electrical conductivity and UC-PL intensity. Related mechanisms for the improvement of UC-PL and electrical properties were discussed. • The SrBi 1.94–0.004 Er 0.06 Yb 0.004 Nb 2 O 9 ceramics possess enhanced electrical properties (2 P r ~ 10.73 μC/cm2, d 33 ~ 15 pC/N). • The excellent photoluminescence of SrBi 1.94- x Er 0.06 Yb x Nb 2 O 9 (SBEN- x Yb) was obtained under 980 nm laser. • The electron band structure reveals the physical origin of the reduced electrical conductivity and improved luminescence. • From experiment to theory, the microstructure and macroscopic properties of SBEN- x Yb system were fully demonstrated. [ABSTRACT FROM AUTHOR]