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The crystallographic structure, dielectric, impedance and piezoelectric properties of novel (0.67 − x)BiFeO3–0.33BaTiO3–x(Na0.5La0.5)TiO3 (NLT100x, x = 0.0, 0.02, 0.04, 0.06, 0.08) ceramics were systematically investigated experimentally. The crystallographic studies showed that different concentrations (Na0.5La0.5)TiO3 doping were well soluble with the BiFeO3 system to form a single pseudo-cubic phase solid solution. The dielectric analysis shows that the doping reduces the leakage current, suppresses the Bi volatilization, expands the dielectric peak, and leads to the evolution of relaxor behavior. Moreover, the large strain (S) of 0.255% and the normalized strain of 430 pm/V were obtained at x = 0.04 and 60 kV/cm, which is attributed to the coexistence of ferroelectric and relaxor domains favoring the domain steering. More importantly, raising the temperature can further improve the strain performance, reaching the maximum strain (Smax) value (~ 0.346%) with the maximum normalized strain of (~ 714 pm/V) at 120 °C and 50 kV/cm. The results show the potential value of the ceramics in piezoelectric actuator applications. [ABSTRACT FROM AUTHOR]

Tribismuth titanium niobium oxide (B 3 TiNbO 9 , BTNO) is one of the Aurivillius phases with the highest Curie temperature (T c), but its piezoelectric coefficient (d 33) is poor. When x = 0.045, high-temperature piezoelectric ceramics with d 33 of 11.9 pC/N and T c of 916.7 °C were prepared by (Mn 1/3 Ta 2/3)(4+ ω)+ modification of Ti4+ at B-site of Bi 2.99 (Li 0.5 Sm 0.5) 0.01 Ti 1- x (Mn 1/3 Ta 2/3) x NbO 9. The substitution will aggravate the distortion of BO6 octahedron due to the displacement of oxygen ions. The existence of Mn3+ in the dopant will act as an oxygen vacancy trap and then increase the resistivity. As a result, BTNO ceramics have enhanced piezoelectric properties as well as temperature and cycle stability. This work provides a theoretical basis for better high-temperature piezoelectric properties of A/B co-doped Aurivillius phase ceramics in the future. [ABSTRACT FROM AUTHOR]

A series of bismuth layer structured ferroelectrics (BLSFs) Bi 3- x (Li 0.5 Sm 0.5) x TiNbO 9 (abbreviated as BTNO-100 x LS, x = 0, 0.01, 0.02, and 0.03) high temperature piezoelectric ceramics were prepared by solid state reaction sintering. The microstructure, piezoelectric properties, and electrical conductivity of the sintered ceramics were studied systematically. The introduction of (Li 0.5 Sm 0.5)2+ ions does not change the bismuth layered structure obviously, but it will overmelt and affect its comprehensive properties with the increase of doping content. At last, the piezoelectric coefficient (d 33) of ∼9.6 pC/N and the Curie temperature (T c) is 921.3 °C, which shows good temperature stability and cycle stability, and the mechanical quality factor (Q m) reaches 2694.3 for x = 0.01 composition. These results show that BTNO-1LS is an excellent candidate for high temperature piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

In this work, (0.64- x)Bi 0.5 Na 0.5 TiO 3 - 0.36Sr 0.7 Bi 0.2 TiO 3 - x (K 0.5 La 0.5)(Ti 0.9 Zr 0.1)O 3 lead-free piezoceramics were designed and fabricated by a conventional solid-phase sintering process. It is found that large strains (0.33 %), low hysteresis coefficients (32 %), and large dynamic d 33 * (367 p.m./V) were obtained at x = 0.01. The large strain originates from the reversible transition of the relaxor to the long-range ferroelectric order in the electric field. When the ferroelectric and relaxor phases coexist in a proper ratio, they can provide a favorable condition for the easier movement of the domains and improve the strain properties. In addition, after 105 cycles, the bipolar strain loop of x = 0.01 content changed slightly, demonstrating excellent fatigue resistance. This work provides a new way to design piezoelectric ceramics with large strain and low hysteresis. [ABSTRACT FROM AUTHOR]

(Bi0.5Na0.5)0.94Ba0.06Ti1−x(Y0.5Nb0.5)xO3 (abbreviated as BNTBT-100xYN) lead-free relaxor ceramics were designed and prepared using a traditional solid-state sintering technique. The influences of the introduction of (Y0.5Nb0.5)4+ complex ions for the dielectric properties and energy storage performances of BNTBT-100xYN ceramics were systematically studied. All samples exhibited a typical pseudo-cubic symmetry structure and obtained the dense microstructure with the uniform distribution of all elements. The ergodic relaxor behavior of all ceramics was observed and revealed a trend of increase as a function of composition. It accelerated the improvement of the temperature stability of the dielectric constant. All samples showed a single grain conduction mechanism and the activation energy decreased with the addition of composition. It is related to the generation of oxygen vacancies induced by the defect dipoles. BNTBT-6YN ceramic revealed excellent dielectric temperature stability within the temperature range from 87 to 479 °C and the loss tangent less than 0.05 between 25 °C and 474 °C. Besides, a high recoverable energy density of ~ 0.91 J/cm3 with the corresponding efficiency of ~ 78.5% at applied 115 kV/cm field was achieved for BNTBT-5YN ceramic. Hence, BNTBT-5YN and BNTBT-6YN ceramics will become one of the outstanding dielectric ceramics for the electronic components. [ABSTRACT FROM AUTHOR]

Polycrystalline Ba(1−x)(La0.50Li0.50)xTiO3 (0 ≤ x ≤ 0.12) ceramics are fabricated via the solid-state reaction technique to analyze their structure, excellent dielectric permittivity, and ferro/piezoelectric characteristics systematically. Powder x-ray diffraction has revealed the pure polycrystalline tetragonal symmetry for x ≤ 0.09 compositions. Rietveld refinement analysis has revealed the structure having a reducing tetragonality with increasing composition. A dense and compact ceramic with many grains having different size distributions has been perceived. The substitution of Li and La ions in BaTiO3 unit cell lattice has increased the ambient temperature dielectric permittivity with reduced loss tangent from ~ 2000, ~ 0.019 (for x = 0) to ~ 5166, ~ 0.002 (for x = 0.09) at 1 MHz frequency. In addition, a high bipolar strain ~ 0.24% for x = 0.03 is obtained. The increase of dielectric permittivity with reduced loss tangent might be applicable for capacitor applications at ambient conditions. [ABSTRACT FROM AUTHOR]

• Three dielectric anomaly peaks were found in a two-layer BLSFs high temperature piezoelectric ceramic for the first time. • The contribution of each ion to the piezoelectric properties was analyzed by conclusion of Rietveld refinement. • (Y 0.5 Sb 0.5)4+-doped BTN ceramic have reduced oxygen vacancies and increased activation energy, resulting in enhanced ceramic performance at high temperature. Bismuth layered material stand out from other piezoelectric materials due to their high Curie temperature (T c) and are often used in high temperature piezoelectric actuators and capacitors. However, its low piezoelectric coefficient (d 33) and dielectric constants (ε′) limit the scope of application of this material. The Bi 3 Ti 0.99 (Y 0.5 Sb 0.5) 0.01 NbO 9 (BTN-1YSb) ceramics by solid state sintering method show improved d 33 (8.1 pC/N), dielectric constants (ε′ ∼2051), temperature stability (d 33 ＞8 pC/N at 800 °C) and mechanical quality factor (Q m ∼ 1834). After Rietveld refinement, it was found that the oxygen element contributed the most to the spontaneous polarization (P s) enhancement of the piezoelectric material. In addition, three dielectric anomalous peaks are observed for the first time in BTNO-4YSb BTN-3YSb ceramics, which is due to the interaction of point defects with domain walls in a wide temperature range. This advantage can be maximized by tuning the dielectric anomaly peak to provide a more stable d 33 at high temperatures. This study analyzes that the contribution of each ion to the piezoelectric properties of BTN-based ceramics and provides a good example for the study of dielectric peaks. [ABSTRACT FROM AUTHOR]

Dielectric ceramics for capacitors have attained significant attention in current time owing to their large power densities and fast charge/discharge rates. Lead-free [(Bi0.50Na0.40K0.10)0.94Ba0.06]1-xLaxTi0.975Ta0.025O3 (abbreviated as BNKBTT-100xLa) relaxor ceramics are prepared using mixed-oxide technique. All ceramics are revealed a pseudo-cubic structure using X-ray diffraction technique. The long-range order existing in BNKBTT-100xLa ceramics is found to reduce with increasing composition. As a result, a highly effective energy storage density (Wrec) ~ 1.558 J/cm3 and efficiency (η) ~ 88.46% is achieved in BNKBTT-2La ceramic. In addition, BNKBTT-2La composition is fatigue-free up to 105 cycles. Also, BNKBTT-4La ceramic exhibits a dielectric constant (ε') ~ 2281 near 150 °C with Δε'/ε'150 °C below 15% over a large range from 39 to 383 °C, showing an outstanding dielectric temperature stability. Therefore, BNKBTT-2La and BNKBTT-4La ceramics are outstanding for energy density and thermally stable dielectric permittivity, respectively, for the device applications. [ABSTRACT FROM AUTHOR]

A synergetic effect of Li/Nd at the A site and W/Mn at the B site co-substitution on electrical properties of calcium bismuth niobate (CaBi2Nb2O9, CBNO)-based ceramics is proposed in this paper. CBNO primarily shows mixed p-type and ionic conduction due to a trace of oxygen vacancies (VO••). Both bulk resistivity (ρb) and activity energy (Ea) for conduction are dramatically increased by the co-substitution in Ca0.92(Li1/2Nd1/2)0.08Bi2Nb2−x(W3/4Mn1/4)xO9 [CBNO-LN-x(WM), x = 0–0.02]. Consequently, the modified compositions almost show an intrinsic conducting mechanism due to a significant suppression of the VO•• concentration. Furthermore, the synergetic effect of Li/Nd at the A site and W/Mn at the B site greatly improves the piezoelectricity coefficient (d33), which is up to ∼21.1 pC/N in the optimized composition [CBNO-LN-10(WM)]. This combined with a high Curie temperature (TC = ∼946 °C) and high resistivity indicates that CBNO-LN-10(WM) is a good promising material in high-temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

Among Aurivillius-phase ferroelectric ceramics, CaBi2Nb2O9 is considered as the best candidate with potential applications in ultrahigh-temperature piezoelectric devices due to the highest Tc (∼940 °C). This paper reports that BiMn co-substitution at A and B sites gives rise to dramatic enchantments in ferroelectricity, piezoelectricity, and electrical resistivity of CaBi2Nb2O9 ceramics. The optimum composition (Ca0.97Bi2.03Nb1.99Mn0.01O9) with a Tc of 953 ± 3°C shows a high ferroelectric remnant polarization (Pr), field-induced strain (S33), piezoelectric activity d33 and d 33 ∗ with values of ∼11.1 µC/cm2, 4.9 × 10−4, 20.8 and 26.1 pC/N, respectively, which are about two to three times those of CaBi2Nb2O9. Significant ferroelectric remnant polarization (Pr = 11.1 µC/cm2), field-induced strain (S33 = 4.9 × 10−4), and piezoelectric activity (d33 = 20.8 pC/N, d 33 ∗ = 26.1 pC/N) are simultaneously induced in ultrahigh Tc CaBi2Nb2O9 piezoceramics by BiMn substitution. [ABSTRACT FROM AUTHOR]

0.94(Bi 0.5 Na 0.5)(Y 0.5 Ta 0.5) x Ti 1- x O 3 -0.06BaTiO 3 lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method to study their excellent electro-strain properties and energy storage characteristics systematically. All ceramics exhibited a dense surface morphology. The introduction of (Y 0.5 Ta 0.5)4+ complex ions destroyed the long-range ferroelectric order, which reduced the T F-R to the operating temperature, resulting in an easier field-induced transition between relaxor and ferroelectric phase. Therefore, for x = 0.01 component attained unipolar strain of 0.37% under 52 kV/cm, and the corresponding normalized strain d 33 * was 708 pm/V. Besides, the destruction of the ferroelectric phase also induced a pinched hysteresis loop and the maximum storage density of 1.215 J/cm3 with the efficiency of 68.7% obtained at 98 kV/cm for BNYT30 ceramics. These all demonstrated that the doping of complex ions (Y 0.5 Ta 0.5)4+ made the BNT-BT an outstanding candidate for actuators and energy storage devices. [ABSTRACT FROM AUTHOR]

A novel (0.67- x)BiFeO 3 -0.33BaTiO 3 - x (K 0.5 Nd 0.5)TiO 3 (KNT100 x , x = 0.0, 0.02, 0.04, 0.06, 0.08 mol%) ceramics were fabricated and their microstructure and electrical properties were studied. All samples displayed a pseudo-cubic symmetry, and adding of KNT had little effect on grain size. The dielectric analysis displayed the dispersion increases with the addition of KNT compositions, showing strong relaxor properties. Besides, high dielectric constant (ε') of 23000 and dielectric peak temperature (T m) of 390 °C remain at 1 kHz in the x = 0.02 sample while the dielectric loss (tanδ) dropped below 0.5 in the range of 30–400 °C, showing excellent electrical insulation performance. In addition, doping of KNT had obvious influence on the strain, and a large strain (Smax) of 0.26% was obtained at x = 0.02 due to the increase of electrical insulation. More importantly, the strain at 50 kV cm−1 enhanced significantly with temperature increasing, reaching a maximum strain of 0.75% with a small hysteresis coefficient of 30% at 110 °C. Particularly, KNT02 exhibited excellent fatigue resistance within 105 fatigue cycles. Presumably these results are attributed to the coexistence of ferroelectric and non-ergodic relaxor domains and the thermally activated domain wall motion. [ABSTRACT FROM AUTHOR]

Abstract: A new type of (0.7−x)Bi0.5Na0.5TiO3‐0.3Sr0.7Bi0.2TiO3‐xLaTi0.5Mg0.5O3 (LTM1000x, x = 0.0, 0.005, 0.01, 0.03, 0.05 wt%) lead‐free energy storage ceramic material was prepared by a combining ternary perovskite compounds, and the phase transition, dielectric, and energy storage characteristics were analyzed. It was found that the ceramic materials can achieve a stable dielectric property with a large dielectric constant in a wide temperature range with proper doping. The dielectric constant was stable at 2170 ± 15% in the temperature range of 35‐363°C at LTM05. In addition, the storage energy density was greatly improved to 1.32 J/cm3 with a high‐energy storage efficiency of 75% at the composition. More importantly, the energy storage density exhibited good temperature stability in the measurement range, which was maintained within 5% in the temperature range of 30‐110°C. Particularly, LTM05 show excellent fatigue resistance within 106 fatigue cycles. The results show that the ceramic material is a promising material for temperature‐stable energy storage. [ABSTRACT FROM AUTHOR]

Novel lead-free [(Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 ] 0.97 La 0.03 Ti 1- x (Al 0.5 Nb 0.5 ) x O 3 ceramics (BNBLT- x AN) were prepared by the conventional solid state sintering method. The dielectric, ferroelectric, ac impedance and energy-storage performance were systematically investigated. Temperature dependent permittivity curves showed that relaxation properties of sintered ceramics gradually diminished with the increase of AN. The introduction of AN gave rise to a slimmer polarization hysteresis loop ( P-E ) and an enhanced dielectric breakdown strength (DBS). Therefore, the optimum energy-storage performance were realized at x  = 0.05 with the energy-storage density ( W rec ) of 1.72 J/cm 3 and energy-storage efficiency ( η ) of 85.6% at 105 kV/cm, accompanied with the excellent temperature stability and fatigue performance. The results demonstrated that BNBLT- x AN system was a promising lead-free candidate for energy-storage applications. [ABSTRACT FROM AUTHOR]

Aurivillius Bi 3 TiNbO 9 has a very high Curie temperature (T c), but the piezoelectric coefficient (d 33) is very low, and the influence of ions with different radii on its performance is not clear. High temperature piezoelectric ceramics Bi 2.99 (Li 0.5 Ln 0.5) 0.01 TiNbO 9 (BTNO-1LiLn, Ln = La, Nd, Gd, and Er) were prepared by solid state reaction sintering, and its microstructure, piezoelectric properties and electrical conductivity were systematically studied. The T c of BTNO-1LiLn increases with the decrease of Ln3+ ions radii. BTNO-1LiEr obtains the highest d 33 of 10.6 pC/N. Considering the cation disorder of A-site and bismuth layer of calcium titanium layer in Aurivilius structure, the crystal structures of BTNO-1LiLa with special occupation and BTNO-1LiEr with the best performance are refined, and the source of spontaneous polarization (P s) is analyzed. It is proved that different occupation will have different effects on the high temperature piezoelectric properties and fatigue cycle properties of BTNO based ceramics. Finally, the band structure of BTNO pure ceramic based on the first principle is calculated. By comparing the activation energy and band gap width, it is indicated that (Li 0.5 Ln 0.5)2+ ions entering BTNO will form impurity energy levels and form p -type semiconductors. This study provides a theoretical basis for better performance of BTNO based high temperature piezoelectric ceramics. [Display omitted] • Discussing the effects of lanthanide ions entering into different sites on the high temperature piezoelectric properties of Bi3TiNbO9. • Analyzing the influence of lanthanide ions entering into different sites on the electrical characteristics of Bi 3 TiNbO 9. • The band structure of pure Bi 3 TiNbO 9 is calculated based on the first principle. [ABSTRACT FROM AUTHOR]

• High temperature piezoelectric properties of BTNO-15WM ceramics were studied. • The influence of ions with different radii on the distortion of BTNO is similar. • The distortion mode of A/B co-doped BTNO is inclined to "tilt" mode. Bi 2.99 (Li 0.5 Sm 0.5) 0.01 Ti 0.985 (W 2/3 M 1/3) 0.015 NbO 9 (abbreviated as B(LS)TNO-15WM, M is Al, Cr, and Sc) were prepared by solid state reaction sintering. The effects of B-site (W 2/3 M 1/3)5+ complex-ion substitution on and their microstructure, piezoelectric properties, and electrical performance were systematically studied. B(LS)TNO-15WCr obtains the highest piezoelectric coefficient (d 33). Through the calculation of XRD refined results, it is found that this is due to its greater distortion of BO6 octahedron. In this work, the possible sources of high performance of BTNO based ceramics doped at B-site are analyzed, which provides a certain theoretical support for future work. [ABSTRACT FROM AUTHOR]

x CeO 2 -doped Bi 0.487 Na 0.427 K 0.06 Ba 0.026 TiO 3 lead-free piezoelectric ceramics (BNTC1000 x , x =0, 0.3, 0.6, 0.8, 1.0, 1.2, 1.4 wt%), were synthesized by the solid-state reaction method. XRD patterns showed that all BNTC1000 x ceramics exhibit pure single perovskite phase. At the critical composition BNTC12, a large electric-field-induced strain of 0.39% with normalized strain ( S max / E max ) of 561 pm/V was obtained under an electric field of 65 kV/cm. The ferroelectric phase was fully poled with electric field, and depoled once the applied electric field was removed. During that cycle, the non-180°-domains repeated switching and back-switching and the large strain was induced. The relaxation behavior was involved in BNTC1000 x ceramics and induced by oxygen vacancy migration. Besides, this behavior was more predominant in BNTC12 than in BNTC0. [ABSTRACT FROM AUTHOR]

Ternary solid solutions of (1 − x)(0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3)- xNaNbO3 (BNKT- xNN) lead-free piezoceramics were fabricated using a conventional solid-state reaction method. Pure BNKT composition exhibited an electric-field-induced irreversible structural transition from pseudocubic to ferroelectric rhombohedral phase at room temperature. Accompanied with the ferroelectric-to-relaxor temperature TF-R shifted down below room temperature as the substitution of NN, a compositionally induced nonergodic-to-ergodic relaxor transition was presented, which featured the pinched-shape polarization and sprout-shape strain hysteresis loops. A strain value of ~0.445% (under a driving field of 55 kV/cm) with large normalized strain of ~810 pm/V was obtained for the composition of BNKT-0.04 NN, and the large strain was attributed to the reversible electric-field-induced transition between ergodic relaxor and ferroelectric phase. [ABSTRACT FROM AUTHOR]

The perovskite oxides (1 − x)Bi0.5(Na0.9K0.1)0.5TiO3- xSrTi0.8Zr0.2O3 (SZT1000 x, x = 0, 0.2, 0.4, 0.6, 0.8, and 1 %) were prepared via the conventional solid-state reaction method. The room temperature ferroelectric P- E loops coordinate with polarization current density J- E curves illustrated the changes of ferroelectric domains and polar nanoregions under different driving fields exhaustively. The composition and electric field dependent strain behavior of this system were investigated to develop a lead-free piezoelectric material with a large strain response at a lower electric field. A large strain of 0.44 % (Smax/Emax = 744 pm/V) at an applied field of 50 kV/cm was obtained at the composition of 0.6 mol% SZT. Temperature-dependent hysteresis measurements reveal the primary origin of the large strain is due to the presence of a nonpolar phase at a zero field. Upon the application of an electric field, the nonpolar phase that can easily transform into a long-range ferroelectric phase, and then brings the system back to its unpoled state once the applied electric field is removed. Notably, the electric field required to deliver large strains is reduced to 40 kV/cm while the Smax/ Emax reached up to 717 pm/V, indicating that the developed material is highly promising for actuator applications. [ABSTRACT FROM AUTHOR]

The field dependence of ferroelectric hysteresis loop and polarization reversal of 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNT-6BT) ferroelectrics at room temperature and 110 °C are investigated. The variation of the hysteresis area suggests three stages of the polarization reversal at the two temperatures, where the first and third stage can be scaled as power law relationships, and the second stage shows non-linear functions. Distinct features in the two temperatures indicate the differences between the domain structures and their external field responses. The reversible field-induced phase transition from relaxor phase to ferroelectric phase at 110 °C plays a key role in getting the large strain. [ABSTRACT FROM AUTHOR]

• Discussing the effects on the structures of (1- x)Ca 0.8 Sr 0.2 TiO 3 - x SmAlO 3 ceramics with the content of SmAlO 3. • Observing excellent temperature stability of dielectric permittivity and low dielectric loss at low frequencies. • Discovering a high-performance microwave dielectric ceramics with ε r = 42.0, Qf = 39,120 GHz, and τ f =-6.4 ppm/℃. (1- x)Ca 0.8 Sr 0.2 TiO 3 - x SmAlO 3 (abbreviated as (1- x)CST- x SA) perovskite ceramics were synthesized through the conventional solid-state reaction process. The effects of SmAlO 3 on the microstructure, low-frequency dielectric performances, and microwave dielectric properties for (1- x)CST- x SA ceramics were investigated systematically. All compositions exhibited an orthorhombic perovskite structure with dense surface morphology. With increasing the content of SmAlO 3 , the order of B-site cation revealed a trend of increase first and then slowly decreased. The presence of oxygen vacancies in the (1- x)CST- x SA ceramics was detected by using x-ray photoelectron spectroscopy. Excellent temperature stability of dielectric permittivity and low dielectric loss (tan δ lower than 0.005) were observed for (1- x)CST- x SA ceramics at low frequencies. For x = 0.35 composition, the temperature coefficient of the resonant frequency approached zero. In addition, the dielectric permittivity of 42.0, the quality factor of 39,120 GHz, and the temperature coefficient of resonant frequency of − 6.4 ppm/℃ were obtained for 0.65CST-0.35SA ceramics. It is suggested that (1- x)CST- x SA ceramics can be used as a candidate material for various microwave communication components. [ABSTRACT FROM AUTHOR]

Modified Aurivillius-type-structured piezoelectric ceramics, LiCeNaBiTiScO (LiCe-NBT-Sc− x, x = 0, 0.025, 0.075, 0.125, 0.15, 0.175) were synthesized by using conventional solid-state reaction process. Rietveld refinement for the x = 0.125 modified sample was carried out by using powder X-ray diffraction and LiCe-NBT-Sc−0.125 was confirmed to be a four-layer Aurivillius oxide with orthorhombic space group A2 am [ a = 5.45814(7) Å, b = 5.43029(7) Å, c = 40.8547(4) Å and V = 1,210.902(26) Å; Z = 4], at room temperature. The Sc/Bi substitution led to an increase in Curie temperatures ( T) and an enhancement in piezoelectric property, and the LiCe-NBT-Sc−0.125 ceramic with a T of 675 °C had a high piezoelectric activity ( d) of 32 pC/N. Variable thermal-annealing d and resistivity ( ρ) of the LiCe-NBT-Sc−0.125 ceramic were investigated; the d of the O annealed sample reached up to 37 pC/N, and its resistivity was about 6.8 × 10 Ω cm at 575 °C and about 6.5 × 10 Ω cm at 650 °C. [ABSTRACT FROM AUTHOR]

LaO (2 wt%)-doped (BiNa)BaTiO (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction. X-ray diffraction (XRD) patterns indicated that LaO has diffused into the lattice of BNBT6 ceramics and formed a solid solution with a pure perovskite structure. Addition of LaO decreased the piezoelectric properties and electrical conductivity. It was used to study the electrical conductivity of the LaO-doped BNBT6 lead-free piezoelectric ceramics combined with electrical modulus and impedance plots at the temperature range over 788-873 K. The values of activation energy derived from the electrical impedance and modulus were found to be 0.51 and 0.50 eV, respectively. The discrepancy between activation energy of relaxation frequency and the activation energy (0.25 eV) of dc electrical conductivity might have been due to a short-range migration or hopping of single ionized oxygen vacancy and a long-range migration or hopping of charge carriers over the whole disordered system, respectively. [ABSTRACT FROM AUTHOR]

Modified ultrahigh-temperature piezoelectric ceramics, Ca1−5xLi2xNd2x□xBi2Nb2−2xScxWxO9−1.5x (CBNO-LiNd-ScW-x, x = 0, 0.01, 0.02, 0.03, 0.04; □ represented A-site vacancies), were synthesized by a traditional solid-state reaction process. XRD Rietveld refinement, TEM, HRTEM and Raman spectroscopy were used to characterize the crystal structures and domain structures of the prepared ceramics. The lithium/neodymium (Li/Nd) and scandium/tungsten (Sc/W) co-substitution as well as the existence of small amounts of A-site vacancies significantly enhanced the ferroelectric and electro-mechanical properties of the CBNO-LiNd-ScW-x ceramics. The Curie temperature (Tc) decreased from 941 °C to 832 °C as the x values increased in CBNO-LiNd-ScW-x, because of an enhancement in the cation disordering between the A site and the bismuth oxide layer. The CBNO-LiNd-ScW-0.01 ceramic with an ultrahigh Tc of 908 °C had a high piezoelectric activity (d33) of 20.6 pC N−1, a large field-induced strain (S33) of 0.27 × 10−3 and a high remnant polarization (Pr) of 6.1 μC cm−2, due to the perfect growth in the ferroelectric domains and the contribution from the reversal of the defect dipoles (VCa′′–VO•• and ScNb′′–VO••); interestingly, it still has a high d33 of 19.5 pC N−1 after up to 800 °C thermal annealing. In addition, the CBNO-LiNd-ScW-0.01 ceramic had a relatively high resistivity of ＞106Ω cm at 600 °C and ＞105Ω cm at 700 °C. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

Lead-free piezoelectric ceramics, (Na0.5Bi0.5) 0.92Ba0.08TiO3 (BNT-BT) have been synthesized by a conventional solid state sintering method. The dependence of temperature on dielectric and ferroelectric properties of lead-free piezoelectric ceramics were investigated. The ceramics exhibit a giant strain with the increase of temperature. The piezoelectric coefficient (d33) is about 149pC/N at RT. The electromechanical properties were explained based on a field induced antiferroelectric-ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

Abstract: (1− x)[0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3]–xBiFeO3 lead-free piezoelectric ceramics (abbreviated as BNKT–BFx with x varying from 0 to 0.10mol) were prepared by solid-state reaction process. Variation of the microstructure and piezoelectric properties of BNKT–BFx ceramics with BF content was investigated. The results indicated that the piezoelectric constant d 33, the planar electromechanical coupling factor k p and mechanical quality factor Q m varied with the BF amount. X-ray diffraction (XRD) analysis showed that the incorporated BF diffused into BNKT lattice to form a solid solution. Scanning electron microscope (SEM) also indicated that BF in high amount affected the microstructure. The morphotropic phase boundary (MPB) with rhombohedral and tetragonal coexistence for the ceramics lies in the range of x =0–0.06 in (1− x)BNKT–xBF system. The optimum values of d 33 and k p are 122pC/N and 0.317 at x =0.04. [Copyright &y& Elsevier]

Abstract: Lead-free ceramics (1− x)(K0.5Na0.5)0.95Li0.05NbO3–xBi0.5(K0.15Na0.85)0.5TiO3 [(1− x)KNLN–xBKNT] with x =0–0.04 were successfully synthesized by conventional solid-state sintering. Effects of Bi0.5(K0.15Na0.85)0.5TiO3 (BKNT) on the phase structure, microstructure and electrical properties of the (1− x)KNLN–xBKNT ceramics were investigated. BKNT strongly affected the sintering behavior, densification and microstructure of the ceramics. X-ray diffraction analysis revealed that all the (1− x)KNLN–xBKNT ceramics possessed pure perovskite structure, showing symmetries of orthorhombic at x <0.005, and tetragonal at x ≥0.015 at room temperature. Coexistence of orthorhombic and tetragonal phases was identified in the range of 0.005≤ x <0.015. The 0.99KNLN–0.01BKNT ceramics showed the optimum piezoelectric, ferroelectric properties and high Curie temperature, which were as follows: d 33 =240pC/N, k p =0.455, P r =20μC/cm2, E c =20.8kV/cm and T c =469°C. The mechanism of the enhanced piezoelectric properties was also discussed. These results indicate that this system looks a promising candidate for lead-free piezoelectric materials. [Copyright &y& Elsevier]

Crystal structures and electrical properties of (Na 0.5 K 0.5 ) 1− x Li x NbO 3 ( x = 0, 0.055, 0.06, 0.065, 0.07; KNN- x Li) ceramics were investigated systematically. Rietveld refinements confirmed that the ceramic with x = 0.06 modification had a typical morphtropic phase boundary (MPB) structure, where the proportions of orthorhombic ( Amm 2) and tetragonal ( P 4 mm ) phases were 58.37% and 41.63%, respectively. However, tetragonal phase structure was predominant in the x = 0.07 ceramic with 75.57% P 4 mm phase. Piezoelectric ceramics KNN- x Li were post-annealed in nitrogen (N 2 ) and oxygen (O 2 ), and atmosphere had a strong impact on the electrical properties of them. O 2 treatment resulted in improvements in ferroelectric polarization, electrostriction characteristic and piezoelectric property, due to the decrease in oxygen vacancy concentration. On the contrary, a deteriorated performance was found in the N 2 -treated samples. Impedance data of KNN- x Li ceramics were largely dominated by the sample bulk, and variable-atmosphere experiments suggested that the KNN-0.06Li ceramic was mainly n -type material. The O 2 -treated KNN-0.06Li ceramic with a T c of 473 °C had a remnant polarization ( P r ) of 29.2 μC/cm 2 , a field-induced strain ( S 33 ) of 0.152%, a piezoelectric coefficient ( d 33 ) of 218 pC/N and an electromechanical coupling factor ( k p ) of 43%. [ABSTRACT FROM AUTHOR]

• BNKTT-1La ceramics achieved an excellent bipolar strain of ∼0.44 % and a large unipolar strain of ∼0.439 % at 60 kV/cm. • The unipolar strain of BNKTT-1La ceramics increased significantly to ∼0.895 % at 100 °C. • BNKTT-1La ceramics exhibited excellent fatigue resistance after 105 cycles at 65 kV/cm. Lead-free piezoelectric ceramics [(Na 0.84 K 0.16) 0.5 Bi 0.5 ] 1- x La x Ti 0.985 Ta 0.015 O 3 (BNKTT-100 x La) were synthesized by traditional solid phase reaction. The influences of La3+ doping on ceramic materials' microstructure, ferroelectric, and dielectric properties were investigated systematically. XRD patterns indicated that La3+ fully diffuse into the BNKTT lattice and form a single solid solution. SEM images showed that the surface of all samples was compact and no heterophase appeared. The ferroelectric-relaxor phase transition temperature gradually moved to low temperature with the increase of La3+ doping, which was beneficial to obtain large electro-strain. The maximum unipolar strain of BNKTT-1La ceramics can reach ∼0.439 % at 60 kV/cm corresponding to the inverse piezoelectric coefficient d 33 ∗ of ∼731 pm/V. The strain performance increased significantly to ∼0.895 % at high temperature because the ferroelectric-relaxor phase transition became easier. The BNKTT-1La ceramics showed excellent fatigue resistance after 105 cycles at 60 kV/cm. All these indicated that BNKTT-100 x La ceramics have great application prospects in piezoelectric brakes, strain sensors, and actuators. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics are promising candidates for energy storage equipment due to their excellent energy-storage properties. Lead-free (1- x)Bi 0.38 Na 0.38 Sr 0.24 TiO 3 - x BaSnO 3 (abbreviated as BNST-100 x BS) relaxor ceramics were synthesized by a traditional solid-phase sintering method. The influences of the addition of BaSnO 3 dopants for the energy storage and dielectric temperature-stable properties of BNST-100 x BS ceramics were systemically investigated. All samples exhibited a typical pseudo-cubic symmetry structure and obtained the dense microstructure. The ergodic relaxor behavior of all ceramics was observed and revealed a trend of increase as a function of composition. All samples showed a single grain conduction mechanism and the activation energy decreased with the addition of composition. It is related to the generation of oxygen vacancies induced by the defect dipoles. BNST-2.5BS ceramic exhibited an outstanding recoverable energy density of ~1.42 J/cm3 with the corresponding efficiency of ~79.7% at 115 kV/cm field. In addition, excellent temperature-stable permittivity (43–255 °C) was obtained for BNST-7.5BS ceramic. Hence, BNST-2.5BS ceramic revealed excellent energy density properties and BNST-7.5BS exhibited outstanding temperature-stable dielectric permittivity, which was beneficial to use in energy storage equipment and other device applications. [ABSTRACT FROM AUTHOR]

(1- x)(Bi 0.5 Na 0.5) 0.94 Ba 0.06 TiO 3 - x AgNbO 3 lead-free piezoelectric ceramics (abbreviated as BNBT-100 x AN) were prepared using the conventional solid-state sintering method. The effects of the introduction of AgNbO 3 (AN) dopants for the dielectric and piezoelectric performances of BNBT-100 x AN ceramics were systematically studied. The XRD patterns and Raman spectra demonstrated that AN as a modifier was successfully diffused into the BNBT-100 x AN lattice and revealed a pseudo-cubic symmetry structure. All samples exhibited a dense surface morphology accompanied by the uniform distribution of elements. A large bipolar strain of ~0.501% and unipolar strain of ~0.481% corresponding to the normalized strain d 33 * of ~740 p.m./V were achieved for BNBT-1AN ceramic at 65 kV/cm field. The BNBT-4AN ceramic exhibited an excellent temperature-stable permittivity with the range from 59 to 380 °C and its dielectric loss was less than 0.02 between 97 °C and 329 °C. These results revealed that BNBT-100 x AN ceramics were more hopeful candidates for actuators, strain sensors, and high-temperature capacitors. [ABSTRACT FROM AUTHOR]

A series of Bi 0.48 (Na 0.84 K 0.16) 0.48 Sr 0.04 (Ti 1- x Ta x)O 3 (abbreviated as NKS-100 x Ta) lead-free piezoelectric ceramics were fabricated using a traditional solid-state method. The structure and electrical properties of NKS-100 x Ta were investigated in detail. The composition for x = 0.01 presented an enhanced electric field induced bipolar strain of ∼0.53%, as well as the giant unipolar strain of ∼0.478% corresponding to S max / E max ∼682 p.m./V at 70 kV/cm. It is found that the ferroelectric-relaxor transition temperature (T F-R) shifted down to ambient temperature and the remnant polarization (P r) decreased with the Ta doping. It destroyed the long-range ferroelectric ordering and increased the relaxor characteristic. Therefore, the origin of giant strain was ascribed to the transformation from the ferroelectric phase to relaxor phase under the applied electric field. In addition, the well fatigue properties within 104 cycles indicated that the prepared ceramics offered extendable availability for sensors and actuators. Fig. 5. (a) Unipolar strain curves of the NKS-100 x Ta measured at 70 kV/cm with 1 Hz frequency. (b) P r , P m and d * 33 as a function of Ta content. Image 1 • A ferroelectric-to-relaxor transition is obtained by chemical modification. • The giant unipolar strain of 0.478% corresponding to S max / E max ∼ 682 pm/V at 70 kV/cm obtained at ambient temperature. • The giant strain derives from the combination of interior and extrinsic effects. [ABSTRACT FROM AUTHOR]

Abstract A series of novel lead-free (1- x)(0.94Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3)- x Sr 0.8 Bi 0.1 □ 0.1 Ti 0.8 Zr 0.2 O 2.95 (SBTZ) ceramics were prepared via a traditional solid state sintering method. The ferroelectric, dielectric, AC impedance and fatigue properties were systematically studied. The introduction of V O and V A decreased the stability of ferroelectric phase, facilitated field-induced relaxor to ferroelectric transition and resulted in pinched and sloped P - E curves. The dielectric properties indicated that the relaxor phase of prepared ceramics was gradually dominated and the temperature of phase transition (T F-R) went downwards to room temperature with the increase of SBTZ. Therefore, a giant unipolar strain of 0.494% with a normalized strain d 33 * of 706 pm/V was obtained at x = 0.06. The AC impedance spectra of x = 0.06 ceramics revealed that its capacitance mechanism was derived from bulk effect. In addition, the stable fatigue resistance properties implied that the prepared ceramics were promising candidates for strain sensors and actuators. [ABSTRACT FROM AUTHOR]

Lead-free piezoceramics (Na (1+ x )/2 Bi (1- x )/2 ) 0.94 Ba 0.06 Ti 1- x Nb x O 3 (BTN100 x ) were prepared using conventional solid-state reaction method. The structures, field- induced strain, AC impedance of sintered ceramics were investigated. The pure perovskite solid solution BTN3 exhibited giant electric-field-induced strain of 0.478% under an electric field of 70 kV/cm at ambient temperature, meanwhile, the normalized strain ( S max / E max ) reached up to 654 pm/V. The giant strain was insensitive to temperature and exhibited excellent fatigue resistance performance within 10 6 switching cycles, making it a promising candidate material for actuator applications. Complex AC impedance spectra confirmed the contribution of grain effect to resistivity behavior. The field-induced giant strain was attributed to the phase transition between ferroelectrics and relaxor ferroelectrics induced by introducing Nb 2 O 5 . [ABSTRACT FROM AUTHOR]

We report a giant strain (0.72%) with a low degree of hysteresis ( ca . 36.2%) and a giant S max / E max ratio (916 pm V −1 , S max and E max denote the maximum strain and the corresponding electric field, respectively) for lead-free (1− x )(0.8Bi 0.5 Na 0.5 TiO 3 -0.2Bi 0.5 K 0.5 TiO 3 )- x Sr 0.8 Bi 0.1 □ 0.1 Ti 0.8 Zr 0.2 O 2.95 piezoceramics with x = 0.06. The giant strain originates from a reversible transition between the ergodic relaxor and ferroelectric states under applied electric fields. A-site vacancies (V A ) and oxygen vacancies (V O ), deliberately introduced to the system, induce a randomly distributed local polarization field. The local field induces embryonic polarization domains that have a broad distribution of maturity and thus smears the transition between the ferroelectric and relaxor states. This leads to a narrow hysteresis loop. The poling field required for the relaxor-to-ferroelectric transition is reduced significantly, due to the remanent ferroelectric phase at zero field acting as the seed, and the point defects synergistically facilitating the nucleation and growth of the ferroelectric phase. Our work provides a novel route for designing piezoelectric materials with both a giant strain and a narrow hysteresis for practical actuator applications. [ABSTRACT FROM AUTHOR]