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Lead-free Ba1-xLaxTi0.91Sn0.09O3 (BLTS) ceramics with x = 0, 0.01, 0.03 and 0.05, were prepared by the traditional solid-state sintering method with calcination and sintering temperatures of 1200 °C for 2 h and 1400 °C for 4 h, respectively. X-ray diffraction (XRD) measurements revealed that all the BLTS ceramics had pure perovskite structures with no detectable impurities. When x = 0 and 0.01, the ceramics exhibited coexisting orthorhombic (O) and tetragonal (T) phases, while the orthorhombic (O), tetragonal (T) and cubic phase (C) were detected in the BLTS ceramics with x = 0.03 and 0.05, which the Rietveld refinement analysis confirmed. Furthermore, increasing x in the BLTS ceramics led to a large decrease in the average grain size (from 45.7 to 0.9 µm). A significant decrease in the remnant polarization (Pr) accompanied by very slim hysteresis loops were observed for higher La (x ≥ 0.03) levels. This demonstrates that BLTS ceramics transition from classical ferroelectric to relaxor ferroelectric behavior due to changing occupancy of the A-site to La3+ from Ba2+. [ABSTRACT FROM AUTHOR]

In this study, the effect of sintering temperature (1000–1100 °C for 2 h) on phase formation, phase transition, microstructure and electrical properties of lead-free piezoelectric (K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 (KNLNTS) solid solution with 0.3 wt%Bi2O3 + 0.4 wt%Fe2O3 + 0.2 wt%CuO additive (abbreviate as modified KNLNTS) was investigated. Modified KNLNTS ceramics were synthesized by the solid-state combustion technique using glycine as fuel. The modified KNLNTS powders were prepared using the calcination condition of 650 °C for 2 h. The XRD pattern of all sintered ceramics exhibited a pure perovskite phase. Using Rietveld refinement to analyze the phase formation showed that the modified KNLNTS ceramics had co-existing phases of orthorhombic and tetragonal in all sintered ceramics and the orthorhombic phase increased when the sintering temperature increased. The average grain size, TO-T, Tc, Pr and Ec increased with increasing sintering temperature. At the sintering temperature of 1025 °C, the modified KNLNTS ceramic showed the best electrical properties (Cε ≈ 6745, Smax ≈0.274% and d*33 ≈ 548 pm/V). The good electrical properties of the modified KNLNTS ceramics makes them good candidates for lead-free applications to replace Pb-based ceramics. [ABSTRACT FROM AUTHOR]

(Ba0.704Sr0.176Bi0.12)1-xZn0.08Nb0.04Ti0.88O3-Nax (BSBZNT-xNa) ceramics with x = 0, 0.01, 0.03 and 0.05 mol%, were prepared by the solid-state combustion technique. The samples were calcined and sintered at 950 °C and 1375 °C, respectively, for 2 h. The phase, microstructure, dielectric, ferroelectric and energy storage properties were investigated. The X-ray diffraction patterns of the BSBZNT-xNa powders showed a perovskite phase for all samples. When x increased from 0-0.03, the average particle size increased from 380 to 480 nm, then decreased to 420 nm. All sintered samples showed the coexistence of the orthorhombic and cubic phases. The average grain size was in the range of 2.03 to 1.39 µm. The BSBZNT-0.01Na ceramic exhibited the highest dielectric properties at room temperature (ɛr = 902, tanδ = 0.10), the lowest remanent polarization (Pr = 0.10 µC/cm2), coercive field (Ec = 0.43 kV/cm), and the highest energy storage efficiency (η ∼ 94.70%) measured under an electric field of 70 kV/cm. [ABSTRACT FROM AUTHOR]

(Bi0.38Na0.30Sr0.28)0.98La0.02Ti1-xZrxO3 (abbreviated as BNSLT1-xZrx, with x = 0 − 0.05) lead free ceramics were fabricated using the solid-state combustion method. The phase structure, microstructure and electrical properties of the ceramics were investigated. The coexistence of the rhombohedral (R) and tetragonal (T) phases was found in all samples. Rietveld refinement confirmed that as x increased from 0 to 0.05, the rhombohedral phase increased from 41 to 60%. A nearly equal R:T phase ratio of 49:51 was obtained for x = 0.01. All ceramics displayed polygonal grain shapes with anisotropic grain growth. The average grain size of the ceramics was in the range of 0.46–0.79 µm. The optimal Zr4+ content resulted in increased grain growth and reduced pores, leading to improved electrical properties. The highest density (5.52 g/cm3), maximum dielectric constant (εm=2156), maximum polarization (Pmax=15.36 µC/cm2) and high energy storage properties (Wtotal=0.49 J/cm3, Wrec=0.45 J/cm3, Wloss=0.05 J/cm3 and η = 90.54% at 60 kV/cm) were obtained from x = 0.01 caused by a morphotropic phase boundary (MPB) and good morphology. [ABSTRACT FROM AUTHOR]

Lead-free (1-x)BiFeO3-xBaTiO3 ceramics (abbreviated as BF-xBT), in a composition range of 0.23 ≤ x ≤ 0.33 mol%, were prepared by the conventional solid-state reaction method. The effect of x content on phase structure, microstructure, magnetic and electrical properties of BF-xBT ceramics is also investigated. With the incorporation of x content, the coexistence of rhombohedral and tetragonal phases was observed. Field emission scanning electron microscope (FESEM) micrographs revealed that the average grain size of BF-xBT ceramics first decreased and then increased with adding x content. The fracture surface of samples showed a mode of inter-granular fracture and intra-granular fracture. The ferroelectric properties were enhanced by adding x ≥ 0.29 mol% in the BF-xBT system. The dielectric and magnetic properties were improved with a maximum value are εr = 888,711, Mmax = 0.40 emu/g, Mr = 0.17 emu/g, and Hc = 3.7 kOe at x = 0.25 mol% [ABSTRACT FROM AUTHOR]

In this study, the phase formation, microstructure, and electrical properties of Sr0.3(Bi0.70Na0.67Li0.03)0.5(Ti1-xNbx)O3: SBNLT-Nbx lead-free ceramics synthesized via the solid state combustion technique were examined. SBNLT-Nbx ceramics with various Nb content of x = 0, 0.01, 0.03, and 0.05 were calcined at 750 °C and sintered at 1175 °C for 2 h, respectively. The SBNLT-Nbx calcined powders showed a perovskite structure and a secondary NbO2 phase was observed with Nb5+ content of 0.03 and 0.05 mol%. All SBNLT-Nbx ceramics exhibited a pure perovskite phase with coexisting rhombohedral and tetragonal phases. The grain size was in the range of 1.17-1.34 µm. The εmax and tan δmax tended to decrease with increased x content. The best ferroelectric and energy storage properties (Pmax = 27.45 µC/cm2, Pr = 1.92 µC/cm2 and Wtotal = 0.958 J/cm3, Wrec = 0.739 J/cm3, Wloss = 0.219 J/cm3, η = 77.1%), measured under an electric field of 70 kV/cm, were observed at x = 0.01. [ABSTRACT FROM AUTHOR]

Lead-free 1-x(Bi0.47Na0.47Ba0.06)0.95La0.05TiO3-xBa(Sn0.70Nb0.24)O3 (BNBLT-xBSN) ceramics with x = 0, 0.01, 0.02, 0.03 and 0.04 mol.% were synthesized by the solid-state combustion technique with a calcination temperature of 750 °C for 2 h and a sintering temperature of 1150 °C for 2 h. The effect of BSN substitution on the phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBLT ceramics was investigated. With the substitution of BSN, the coexisting rhombohedral (R) and tetragonal (T) phases transformed into coexisting R and cubic (C) phase, verified by Rietveld refinement. The C phase increased with increased BSN content. The average grain size decreased from 1.14 to 0.89 µm when x increased to 0.03 and then increased to 0.96 µm. The measured density and maximum dielectric constant (εm) tended to increase from 5.44 to 5.87 g/cm3 and 1800 to 1942 when x increased to 0.03, then decreased to 5.25 g/cm3 and 1501, respectively. The remanent polarization (Pr) and coercive field (Ec) decreased when x increased to 0.03. The 0.97BNBLT-0.03BSN ceramic exhibited the lowest energy loss density (Wloss ∼ 0.10 J/cm3) and the highest energy-storage efficiency (η ∼ 77.3%) measured under an electric field of 70 kV/cm. [ABSTRACT FROM AUTHOR]

(1 − x)[(K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3] − xBi0.8Ba0.2FeO3 [(1 − x)KNLNTS-xBBF] lead-free ceramics, with different x contents, were prepared by the solid-state combustion technique. The effect of Bi0.8Ba0.2FeO3 content on the phase formation, microstructure, and electric and magnetic properties of KNLNTS ceramics were investigated. The KNLNTS ceramic exhibited co-existing orthorhombic and tetragonal phases. When x increased, the samples demonstrated an increased tetragonal phase and unit cell volume. The average grain size, density and relative density deceased when x increased up to 0.06 and then continuously increased. For x = 0, a well-saturated P–E loop was found in which the Pr and Ec values were about 21.27 μC/cm2 and 12.38 kV/cm, respectively. However, x = 0.02–0.2 exhibited a round P–E loop because the leakage current was performed. For higher x, the leakage current of the samples decreased, suggesting that the samples exhibited slim P–E loops. The KNLNTS ceramic exhibited diamagnetic behavior while the x = 0.02–0.4 samples showed ferromagnetic behavior. At room temperature, multiferroic behavior, which exhibited fair ferroelectric and ferromagnetic hysteresis loops, was obtained from the samples with x = 0.3–0.4, which means these ceramics can be applied in multifunctional devices. The maximum magnetoelectric coupling (αE) was obtained from the KNLNTS-xBBF with x = 0.4. [ABSTRACT FROM AUTHOR]

Lead-free ceramics of 0.6Bi0.5Na0.5TiO3-0.4Sr0.7Bi0.2TiO3 (BNT-SBT) were prepared by the solid-state combustion technique using glycine as fuel. The samples were calcined and sintered from 700 to 900 °C for 2 h and from 1100 to 1175 °C for 2 h, respectively. Their phase structure, microstructure and electrical properties were investigated. The XRD and Rietveld refinement results of the ceramic samples showed coexisting rhombohedral and tetragonal phases, with a ratio of 56:44 at a sintering temperature of 1150 °C. The average grain size and the measured density increased with increased sintering temperatures. The highest dielectric, ferroelectric and energy storage properties (εmax=3142 and tan δmax=0.041, Pmax=27.09 μC/cm2, Wtotal=1.099 J/cm3, η = 81.3% and Pes=1.16%) were obtained from the sample sintered at 1150 °C. [ABSTRACT FROM AUTHOR]

In this research, the effects of calcination temperature in a range of 1050–1200 °C for 2 h and sintering temperature in a range of 1325-1400 °C for 2 h on phase formation, microstructure and electrical properties of lead-free Ba0.9Ca0.1TiO3 (BCT) ceramics fabricated via the solid-state combustion technique were investigated. For the XRD result, all the ceramics exhibited a coexisting phase between tetragonal and orthorhombic. The ceramic grain size tended to increase with increase of the sintering temperature. For BCT ceramic produced by the optimum sintering temperature (1375 °C for 2 h), the dielectric, ferroelectric and piezoelectric properties of εC=7393, Pr=7.60 μC/cm2,EC=5.99 kV/cm and d33=158 pC/N, respectively, were obtained. [ABSTRACT FROM AUTHOR]

Lead-free [(Bi0.5Na0.5)0.94Ba0.06]1-xLaxTiO3 (BNBT-xLa) ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol.% were synthesized by the solid-state combustion technique with calcination and sintering temperatures of 750 °C and 1150 °C, respectively, for 2 h. The phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBT-xLa ceramics were investigated. The XRD patterns of the powders showed a pure perovskite phase for all samples. The average particle size increased from 298 to 379 nm with increasing x. All ceramics showed coexisting rhombohedral and tetragonal phases. When x rose, the content of the tetragonal phase increased, as validated by the Rietveld refinement method. The average grain size decreased from 1.43 to 0.81 µm when x increased from 0 to 0.05 and then started to increase. The Curie temperature (Td) of the samples shifted to lower temperatures with rising x, owing to an increased tetragonal phase. The maximum dielectric constant (εm), remanent polarization (Pr) and coercive field (Ec) decreased with increasing x. The BNBT-0.05La ceramic exhibited the smallest grain size, and lowest Pr = 0.8 µC/cm2 and Ec = 2.9 kV/cm, with the highest energy storage efficiency (η ∼ 78.31%) and a large effective energy storage density (W ∼ 0.83 J/cm3) measured in an electric field of 80 kV/cm. [ABSTRACT FROM AUTHOR]

Lead-free (K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) ceramics with Li+ substitution (KN0.5-xLixNT) and direct (KNNT-xLi) doping at x = 0, 0.01, 0.02, 0.03 and 0.04 mol% were synthesized by the solid-state combustion route. The phase, microstructure, dielectric and ferroelectric properties of the ceramics were examined. The XRD pattern of the ceramics revealed orthorhombic and tetragonal phases in all specimens. The Rietveld refinement procedure showed that increasing either the Li+ substitution or doping levels enhanced the amount of the tetragonal phase. It was found that Li+ doping, either substitutional or additional, enhanced the Curie temperature (TC) by increasing the tetragonal distortion, while the dielectric constant (εC) decreased. The good remanent P-E loops of the KN0.5-xLixNT ceramics were found with x = 0.01 (Pr∼10.89 µC/cm2 and EC∼13.09 kV/cm), while for KNNT-xLi ceramics, it was obtained with x = 0.02 (Pr∼15.65 µC/cm2 and EC∼11.46 kV/cm), which were confirmed by remanent P-E hysteresis measurements. [ABSTRACT FROM AUTHOR]

This research studied the effect of MnO2 substitution on the phase formation, microstructure and electrical properties of (Ba0.97Ca0.03)(Ti0.94-xMnxSn0.06)O3 (BCTMS with x = 0, 0.005, 0.010, 0.015, and 0.020 mol%) lead-free piezoelectric ceramics. The BCTMS ceramics were fabricated by the solid-state combustion technique. The powders and green pellets were calcined and sintered at 1100 °C for 4 h and 1400 °C for 2 h, respectively. The XRD patterns of all BCTMS ceramics exhibited a single perovskite structure with the coexisting orthorhombic and tetragonal phases, where the tetragonal phase increased and the orthorhombic decreases with increasing x. The average grain size decreased from 35 to 13 µm with increasing x. The dielectric constants at room temperature (εr) and at the Curie temperature (εC), density, remanent polarization (Pr), and piezoelectric coefficient (d33) decreased as x increased. The changes in the crystal structure and microstructure affected electrical properties. [ABSTRACT FROM AUTHOR]

This research studied the effect of W4+ substitution on the phase formation, microstructure and electrical properties of (Ba0.97Ca0.03)(Ti0.94-x/2Sn0.06-x/2Wx)O3 (BCTSW) ceramics with x = 0, 0.005, 0.010, 0.015 and 0.020 mol%. The BCTSW ceramics were synthesized by the solid-state combustion technique, using glycine as fuel. The powders and green pellets of BCTWS were calcined and sintered at 1100 °C for 4 h and 1400 °C for 2 h, respectively. A pure perovskite phase with coexisting orthorhombic and tetragonal phases were observed for all samples. The content of the tetragonal phase increased when x rose, as verified by the Rietveld refinement procedure. The average grain size and the measured density of the samples tended to decrease from 35 ± 0.56 to 1.9 ± 0.12 µm and 5.59 to 4.88 g/cm3, respectively, when x increased. The dielectric behavior of the ceramics strongly degenerated upon W4+ substitution. The undoped BCTS ceramic showed a well-saturated P-E hysteresis loop. With W4+ substitution, the samples' P-E loops became unsaturated and a leakage current was created. [ABSTRACT FROM AUTHOR]

Lead-free [(0.76-x)Bi0.5Na0.5TiO3–0.24SrTiO3–x(K0.5Na0.5)NbO3; BNT-ST-KNN] ceramics with x = 0, 0.03, 0.05, 0.07, 0.10, 0.15 wt.% were synthesized by using a solid-state reaction method. The effect of x content on phase, microstructure electrical and energy density properties was investigated. The samples were analyzed by X-ray diffraction (XRD) and the XRD patterns were fitted using the Rietveld refinement. The grain growth is obviously inhibited and smaller grains are formed in the ceramic samples at a high concentration of x. Dielectric study confirmed relax or nature with a drastic decrease of Tmax with the increase of x content in BNT-ST-KNN system. The maximum density (ρ = 5.42 ± 0.13 g/cm3), highest dielectric constant (εr=3300) with tanδ∼0.05, high recoverable energy storage density (Wrec=0.16 J/cm3) with energy storage efficiency of (η = 64) were obtained in x = 0.03 wt.% ceramic samples, which suggested its usefulness for energy-storage capacitor applications. [ABSTRACT FROM AUTHOR]

Lead-free Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 + 0.003 mol Sm2O3 (BNKLT-Sm) ceramics were synthesized via the solid-state combustion technique with calcination temperatures between 750 and 850 °C and sintering temperatures between 1025 and 1100 °C for 2 h. The results showed that increasing the calcination temperature caused the percentage of perovskite phase and the particle size of the BNKLT-Sm powders increased. The BNKLT-Sm powder calcined at 800 °C displayed a pure perovskite structure without any impurity phases. The influence of the sintering temperature on the phase formation, microstructure and electrical properties of the ceramics was then investigated. All samples sintered at different temperatures possessed coexisting rhombohedral (R) and tetragonal (T) phases and the R phase became dominant when the sintering temperature increased. The microstructure of all ceramics showed a rectangular shape and anisotropic growth. The average grain size increased with increasing sintering temperature. Dielectric and ferroelectric behavior displayed relaxor characteristics in all samples. The maximum dielectric constant at Tm (εm) of 4777 and the highest remnant polarization (Pr) of 5.03 µC/cm2 were obtained by the densest ceramics (5.85 g/cm3), which was sintered at 1075 °C for 2 h. [ABSTRACT FROM AUTHOR]

Lead-free (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3-xNiO (x = 0, 0.2, 0.4, 0.6 and 0.8 wt%) ceramics were prepared by the solid-state combustion technique using glycine as a fuel. The effect of NiO doping on the phase formation, microstructure, electrical and magnetic properties of the ceramics was investigated. The powders and ceramics were calcined and sintered at a temperature of 1050 °C and 1450 °C for 2 h, respectively. XRD results showed that all ceramics had coexisting orthorhombic and tetragonal phases. Increasing the amount of NiO doping enhanced the amount of tetragonal phase, as verified by the Rietveld refinement technique. The density values (ρ) and the average grain size rapidly decreased from 5.79 to 4.69 g/cm3 and 37.8 ± 3.6 to 3.0 ± 0.3 µm when NiO doping increased from 0 to 0.8 wt%. The values of the dielectric constant (ε), dielectric loss (tan δ) and remnant polarization (Pr) tended to decrease when NiO doping increased. Only the sample with 0.4 wt% NiO exhibited ferromagnetic behavior at room temperature, with a remnant magnetization (Mr) and a coercive field (Hc) of 1.04 × 10−5 emu/g and 72.55 Oe, respectively. [ABSTRACT FROM AUTHOR]

The effects of Cs+ substitution and direct doping in (K0.5Na0.5)(Nb0.7Ta0.3)O3 (KNNT) ceramics, on the crystal structure, microstructure and electrical properties were investigated. Both the KNNT with Cs+ substitution (K0.5-xCsxNNT) and addition (KNNT-xCs) (x = 0, 0.01, 0.02, 0.03 and 0.04 mol%) were synthesized by the solid-state combustion technique using glycine as fuel. All samples were sintered at 1130–1150 °C for 4 h. The x-ray diffraction (XRD) analysis for the ceramics revealed the presence of orthorhombic (O) and tetragonal (T) phases in all samples. Increasing both the Cs+ substitution and doping amounts, enhanced the content of orthorhombic phase, as verified by the Rietveld refinement technique. It was found that Cs+ doping, either substitutional or additional, strongly decreased their density, dielectric and ferroelectric properties. The undoped KNNT ceramic exhibited well-saturated P-E hysteresis loop. With Cs+ doping, the samples became unsaturated and a leakage current was produced. The KNNT-xCs ceramics demonstrated higher density and dielectric properties than the K0.5-xCsxNNT ceramics. [ABSTRACT FROM AUTHOR]

This article reports the effect of Cu2+ substitution on the phase formation, morphology and electrical behavior of Bi0.5Na0.34K0.11Li0.05Ti(1-x)CuxO3 with 0 ≤ x ≤ 0.020 (BNKLT-xCu) ceramics prepared by the solid state combustion technique with glycine used as the fuel. All samples were prepared with a calcination temperature and a sintering temperature of 750 °C and 1025 °C, respectively for 2 h. The XRD results of all compositions revealed a single perovskite structure and that Cu2+ diffused efficiently into B-sites of the lattice, producing a BNKLT-xCu solid solution. The phase formation of the BNKLT-xCu ceramics showed coexisting rhombohedral (R) and tetragonal (T) phases in all samples. The highest measured density of the BNKLT ceramics was 5.99 g/cm3 and good dielectric properties measured at the temperature of the maximum dielectric constant (εm = 4723 and tanδ = 0.054), were obtained by the sample with Cu2+ substituted at x = 0.010. The BNKLT-xCu ceramics with Cu2+ ≥ 0.005 showed pinched P-E loops, and the negative strain of the S-E loops started to disappear, owing to the Cu2+ induced transformation from the ferroelectric (FE) phase to the ergodic relaxor (ER) phase. With Cu2+ levels of 0.010, the d*33 value increased to 705 pm/V, indicating that this sample was near the FE–ER phase boundary with induced high strain. Substituting an appropriate amount of Cu2+ improved the densification of BNKLT-xCu ceramics as capillary forces in the liquid phase during sintering pulled the grains together, which increased the εm values. [ABSTRACT FROM AUTHOR]

Lead-free 0.94Bi0.50Na0.50TiO3–0.06Ba0.85Ca0.15Ti0.90Zr0.10O3–xmol%Bi2FeCrO6 ceramics, with x = 0–0.021 (BNT–BCTZ–xBFCO), were calcined at 650 °C for 2 h and sintered at 1150 °C for 2 h using the solid-state combustion technique. The effect of BFCO content (x) on the phase formation, microstructure, electrical and magnetic properties was studied. The sintered pellets exhibited a pure perovskite phase with the coexistence of rhombohedral (R3c) and tetragonal (P4bm) phases in all the studied compositions. The percentage of R3c increased as x increased from 0 to 0.013, before decreasing, as obtained from the Rietveld refinement analysis (Fullprof). A morphotropic phase boundary of BNT–BCTZ–xBFCO ceramics was observed at x = 0.013, and the ratio between the rhombohedral and tetragonal phases of this composition was 51.0:49.0. The scanning electron microscopy analysis showed polyhedral-shaped grains whose average size increased with increase in the BFCO content (x). The appropriate amount of BFCO doped into BNT–BCTZ ceramics enhanced the electrical, ferroelectric and piezoelectric properties. At optimum doping (x = 0.013), the sample exhibited the highest relative density (98.2%), a high dielectric constant (εR = 1572 and εm = 5137), maximum remanent polarization (Pr = 42.41 µC/cm2), low coercive field (Ec = 33.57 kV/cm), maximum piezoelectric coefficient (d33 = 241 pC/N) and the highest normalized strain ( d 33 ∗ = Smax/Emax = 765 pm/V). These improvements to BNT–BCTZ make the ceramic a potential candidate for use in capacitors, sensors and actuators. The magnetic properties also changed with different BFCO content (x). The sample with x = 0 showed diamagnetic behavior, while the samples with 0.003 ≤ x ≤ 0.021 exhibited a paramagnetic behavior with higher magnetization at higher BFCO content. [ABSTRACT FROM AUTHOR]

The aim of this work is to improve the electrical properties of BNKLLT ceramics with the addition of BCTZ. New binary (1 − x)BNKLLT- xBCTZ lead-free piezoelectric ceramics with different x contents between 0 and 0.10 (step 0.02) were fabricated by the solid-state combustion technique, where glycine was used as a fuel. The influences of x concentration on the phase evolution, morphology, and electrical behavior were investigated. The phase formation exhibited a coexistence of rhombohedral and tetragonal phases in all samples. With the increasing x content, the phase formation was dominated by a higher tetragonality. The average gain size continuously reduced from 1.52 to 0.96 µm when x content was increased. The maximum dielectric temperature ( T) of these ceramics decreased with the increasing x content. The ferroelectric properties were further weakened with the increasing x content. The MPB region was obtained at x content of around 0.04 producing this sample and showed the highest dielectric constants ( ε = 2720 and ε = 6110) and an excellent piezoelectric constant ( d = 295 pC/N). [ABSTRACT FROM AUTHOR]

This work studied the effect of firing conditions on phase formation, microstructure and electrical properties of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3;(abbreviated as BCTZ) ceramics, which were synthesized through the combustion technique. To reduce the reaction temperature, glycine was used as fuel with a ratio of raw material: glycine (1:1.11). BCTZ samples were calcined at 900–1200°C for 2 h and sintered at 1350 –1550°C for 2 h. Ultrafine BCTZ powder and single peroveskite phase were achieved from the sample calcined at 1050°C for 2 h.These results were obtained at a lower temperature and with shorter dwell time than those obtained using the solid state reaction method by ∼150°C and 1 h, respectively. The BCTZ ceramics exhibited a coexistence of rhombohedral and orthorhombic phase in all samples. The average particle size and the average grain size increased from 172 to 295 nm and 0.82 to 2.57 µm, respectively, when firing temperatures increased. The highest density (5.76 g/cm3), highest dielectric constant (ϵr≅ 4485 andϵmax≅ 14897) and best ferroelectric properties (Pr≅ 18.47 μC/cm2andEC≅ 4.52 kV/cm) were obtained from the sample sintered at 1450°C for 2 h. [ABSTRACT FROM AUTHOR]

The 0.68Bi0.5Na0.5TiO3–0.22Bi0.5K0.5TiO3–0.10Bi0.5Li0.5TiO3(BNKLT) lead-free ferroelectric ceramics were prepared by the combustion technique. The BNKLT was calcined from 600°C to 850°C for 2 h and sintered from 900°C to 1050°C for 2 h. The XRD diffraction pattern was indexed on the basis of rhombohedral perovskite structure. The secondary phases K4Ti3O8and K2Ti6O3were detected in the powders calcined below 750° C. The highest perovskite percentage was observed in the powders calcined above 750°C. The sintered pellets showed single-phase perovskite structure for all samples, which indicated that K+, Bi+and Li+ions substituted onto the A-site in the BNKLT lattice to form a solid solution. The increase in sintering temperature up to 1025°C significantly promoted grain growth and microstructure densification. The depolarization temperature (Td) of the sample shifted to higher temperatures whereas the temperature of maximum permittivity (Tmaxε) shifted to lower temperatures with an increase in sintering temperature. The optimum dielectric properties were obtained from the sample sintered at 1025°C with ϵr= 4,340 (atTmaxε), density (ρ = 5.79 g/cm−3) and shrinkage (∼18.4%). [ABSTRACT FROM AUTHOR]

A lead-free 0.97(K0.5Na0.5NbO3)-0.03(Bi0.5Na0.5TiO3); KNN-BNT ceramic has been fabricated by the combustion technique using urea as a fuel. The precursors were calcined at 600–900°C for 3 h and then sintered at 1000–1100°C for 2 h of dwell time. A pure perovskite phase was found in the powders calcined above 700°C which is lower than the calcination temperature of the solid state reaction method ∼200°C. The pellets sintered below 1050°C illustrated a 100% of perovskite phase. The microstructure demonstrated a square and rectangular shape of grains. The average grain size and linear shrinkage increased with the increasing of sintering temperatures. The densest ceramic was discovered in the sample sintered at 1050°C. The DSC result indicated that the Curie point significantly changed with various sintering temperatures. [ABSTRACT FROM AUTHOR]

Environment-friendly piezoelectric micro/nanogenerators have attracted tremendous attention due to the increasing demand for portable self-power devices. Here, the [(0.94−x)Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 –xK 0.5 Na 0.5 NbO 3 ; BNT-BT-xKNN] lead-free ceramic, at x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 mol%, was prepared via the solid-state method. The doping concentration x = 0.02 mol% shows the highest dielectric properties and the lowest dielectric loss. The active layer of the hybrid device is made by mixing BNT-BT-2KNN into the PDMS to form a series of polymer-ceramic composite films ranging from 7 to 19 wt% of BNT-BT-2KNN. The electrical response of the composite film is systematically studied with the addition of different weight percentages of the particles to the PDMS matrix. It was found that incorporating BNT-BT-2KNN at 11 wt% into the PDMS matrix exhibited the optimum harvesting performance, resulting in an output voltage and current density of about 30 V and 0.28 μA/cm2, respectively. The hybridized PENG and TENG devices could operate in a long-term cyclic mode, charge the capacitor for energy storage, and also light up LEDs. This research proposed a simple device fabrication and provided a guideline for the development of high-performance microgenerators, which is crucial for device development and practical use in the future. [ABSTRACT FROM AUTHOR]

In this study, the influence of La3+ substitution on the phase structure, microstructure, electrical and energy storage properties of (Sr 0.3 Bi 0.35 Na 0.335 Li 0.015) 1-x La x TiO 3 (SBNLT-xLa) ceramics with x = 0–0.05, using the solid-state combustion technique, was investigated. X-ray diffraction (XRD) patterns indicated a pure perovskite structure formed, along with coexisting rhombohedral and tetragonal phases in all ceramics. The Rietveld refinement analysis showed the tetragonal phase increased while the rhombohedral phase decreased with increased La3+ content. The morphology of the SBNLT-xLa ceramics displayed polygonal grain shapes and anisotropic grain growth. Average grain sizes increased from 2.01 to 2.43 μm as x increased from 0 to 0.01 and afterwards decreased as x increased further. Both the measured density and maximum dielectric constant (ɛ m) decreased from 5.48 to 5.29 g/cm3 and from 4667 to 2313, respectively, when x increased from 0 to 0.05. A decrease in the dielectric properties caused by the phase ratio shifting away from a morphotropic phase boundary (MPB) condition, poor microstructure and low density was produced with La3+ replacement. The maximum polarization (P max), remnant polarization (P r) and coercive field (E c) decreased with increased La3+ content. A decline in P r and E c improved the energy storage efficiency (ƞ) and energy storage loss (W loss), resulting in enhanced energy storage properties. At x = 0.02, the ceramic showed good energy storage properties (W total of 0.781 J/cm3, W rec of 0.624 J/cm3, W loss of 0.157 J/cm3 and ƞ of 79.8%), measured at 60 kV/cm. [ABSTRACT FROM AUTHOR]

This work investigates the effect of CuO doping (0–1.0 wt%) on the phase formation, microstructure, electric, and magnetic properties of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 (BCTZ) ceramics. These samples are fabricated by the solid state combustion technique using glycine as fuel. The powders and ceramics are calcined and sintered at 1050 and 1450 °C, respectively, for 2 h. The coexistence of the orthorhombic and tetragonal phases is observed in all samples. Increasing the amount of CuO doping enhances orthorhombicity, as verified by the Rietveld refinement technique. The orthorhombic and tetragonal phases are close to equal in the 0.4 wt% CuO doped sample. The grain size continuously increases as more CuO is added up to 0.4 wt% and then the size decreases due to the accumulation of excessive CuO at the grain boundaries. The density, dielectric constant, and ferroelectric properties tend to be enhanced when the CuO doping increase from 0 to 0.4 wt%, then they start to degrade. By increasing the CuO concentration from 0 to 0.8 wt%, the ceramics exhibit diamagnetic behavior. A ferromagnetic hysteresis loop is observed in the ceramic with 1.0 wt% CuO doping when measured at a temperature of 50 K. [ABSTRACT FROM AUTHOR]

Lead-free solid solutions (1- x - y )Bi 0.5 Na 0.5 TiO 3 – x Bi 0.5 K 0.5 TiO 3 – y BaZr 0.05 Ti 0.95 O 3 (0≤ y ≤0.25 and 0.10≤ x ≤0.30) were prepared by using a solid-state reaction method. The effect of y (BZT) and x (BKT) contents on phase, microstructure, and electrical properties was investigated. The XRD and Raman spectra exhibited co-existing rhombohedral and tetragonal phases throughout the entire compositional range with the tetragonal phase becoming dominant at higher y (BZT) and x (BKT) concentrations. While an increased in y (BZT) content promotes grain growth, the addition of x (BKT) suppresses it. The diffuseness exponent ( γ ) of ceramics increased from 1.82 to 1.92 and from 0.05 to 1.77 when increased of y (BZT) and x (BKT) contents, respectively, which showed the diffuse phase transition behavior. The change in P - E loops of ceramics was closely related to relative stability of long-range order. The results reflected a competition between compositions induced tetragonality and disorder. It appears that small amount of x (BKT) and y (BZT) favor ergodic behavior, which is indicative of increased disorder and stable PNRs at zero field conditions. However, with increased amount of x (BKT) and y (BZT), non-ergodic behavior is re-introduced, most likely due to increased tetragonality. The results indicated that the addition y (BZT) and x (BKT) significantly enhances the field-induced strain in (1- x - y )Bi 0.5 Na 0.5 TiO 3 – x Bi 0.5 K 0.5 TiO 3 – y BaZr 0.05 Ti 0.95 O 3 ceramics. [ABSTRACT FROM AUTHOR]

Lead-free [(Bi0.5Na0.5)0.94Ba0.06]1-xLaxTiO3 (BNBT-xLa) ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mol.% were synthesized by the solid-state combustion technique with calcination and sintering temperatures of 750 °C and 1150 °C, respectively, for 2 h. The phase formation, microstructure, dielectric, ferroelectric and energy storage properties of the BNBT-xLa ceramics were investigated. The XRD patterns of the powders showed a pure perovskite phase for all samples. The average particle size increased from 298 to 379 nm with increasing x. All ceramics showed coexisting rhombohedral and tetragonal phases. When x rose, the content of the tetragonal phase increased, as validated by the Rietveld refinement method. The average grain size decreased from 1.43 to 0.81 µm when x increased from 0 to 0.05 and then started to increase. The Curie temperature (Td) of the samples shifted to lower temperatures with rising x, owing to an increased tetragonal phase. The maximum dielectric constant (εm), remanent polarization (Pr) and coercive field (Ec) decreased with increasing x. The BNBT-0.05La ceramic exhibited the smallest grain size, and lowest Pr = 0.8 µC/cm2 and Ec = 2.9 kV/cm, with the highest energy storage efficiency (η ∼ 78.31%) and a large effective energy storage density (W ∼ 0.83 J/cm3) measured in an electric field of 80 kV/cm. [ABSTRACT FROM AUTHOR]

The effects of A-site Li- or B-site Fe-doping into 0.93(Bi 0.5 Na 0.5)TiO 3 -0.07BaTiO 3 (BNBT) ceramics were systematically investigated for the compositional ranges of (Bi 0.465 Na 0.465 Ba 0.07) 1- x Li x TiO 3 (BNBT- x Li) and (Bi 0.465 Na 0.465 Ba 0.07)Fe x Ti 1- x O 3 (BNBT- x Fe) (x = 0.01–0.03). The R3c / P4bm phase ratio remained essentially unchanged across the entire set of Li and Fe doping levels studied. Although some typical characteristics for acceptor doping were observed for both BNBT- x Li and BNBT- x Fe, their ferroelectric and piezoelectric properties were different. A clear transition from a slim (BNBT, E c = 17.0 kV/cm, P r = 22.9 μC/cm2) to square-like P-E hysteresis loops (E c = 29.9 kV/cm, P r = 33.9 μC/cm2) was observed in BNBT- x Li at x ≥0.02. In contrast, constricted P-E loops (E c = 13.0–15.7 kV/cm and P r = 28.6–31.7 μC/cm2) and deformed butterfly S-E curves were detected in all BNBT- x Fe ceramics. These results suggest A-site Li doping as a more effective method for stabilizing the non-ergodic relaxor phase in BNT-BT ceramics, which could help further tailor the piezoelectric properties in other A-site doped Bi-based perovskite systems. [ABSTRACT FROM AUTHOR]

Abstract: Lead-free piezoelectric 0.992(0.95K0.5Na0.5NbO3–0.05LiSbO3)–0.008BiScO3; KNN-LS-BS ceramics were successfully prepared using the combustion method. The highest % perovskite phase was found in the sample calcined at 700°C for 1h. The structural phase of orthorhombic structure was also detected in this sample. For the sintered ceramics, a pure tetragonal perovskite phase was observed in the samples sintered between 1025 and 1100°C. The microstructure of ceramics showed a square or rectangular shape and the average grain size increased with increasing of sintering temperature. The density of the ceramics increased with increasing of sintered temperature up to 1075°C, were it reached 97.5% of theoretical density and then dropped in value when the sintered temperature further increased. The excellent electrical properties of ε r at T c =6600, tanδ at T c =0.04, P r (at 40kV/cm)=19.4μC/cm2 and E c (at 40kV/cm)=24.1kV/cm were obtained in the most dense ceramic. The results indicate that the KNN-LS-BS ceramics are promising lead-free piezoelectric materials. [Copyright &y& Elsevier]

Bi 0.5 Na 0.34 K 0.11 Li 0.05 Ti 1-x Ni x O 3-δ (BNKLT-xNi with x = 0, 0.005, 0.010, 0.015 and 0.020) lead-free piezoelectric ceramics have been synthesized by the solid-state combustion technique. The effect of x on the phase formation, microstructure, electrical and magnetic properties were investigated. A pure perovskite phase was obtained from all samples. Coexisting tetragonal and rhombohedral phases were found in all samples and the rhombohedral phase increased with increasing x, which was detected by XRD, Raman spectroscopy and XAS with the EXAFS technique. Moreover, the EXAFS technique provided the quantity of the rhombohedral phase, that increased from 38.8% to 57.0% when increasing x from 0 to 0.020. The morphotropic phase boundary (MPB) was identified at an x content of 0.010, with the ratio of the tetragonal to rhombohedral phases being 49.5:50.5%. This composition exhibited a high dielectric constant, at T m of 5428, a maximum strain of 0.170%, with a piezoelectric coefficient factor (d 33 ∗) of 340 p.m./V and large ferroelectric properties (P r of 26.1 μC/cm2 and E c of 17.9 kV/cm). Furthermore, the saturation magnetization (M s) at room temperature was increased by increasing x content. • BNKLT-0.010Ni showed MPB region with rhombohedral:tetragonal phase of 50.5:49.5%. • EXAFS revealed that the tetragonal phase continuously decreased from 61.2 to 43.0%. • Oxygen vacancy content was increased with increasing Ni substitution. • At the MPB composition, high S max (0.17%) and d 33 ∗ (340 p.m./V) were obtained. [ABSTRACT FROM AUTHOR]

(1−x)[(K 0.44 Na 0.52 Li 0 .04 )(Nb 0.84 Ta 0.10 Sb 0.06 )O 3 ]-x[(Ba 0.85 Ca 0.15 )(Ti 0.90 Zr 0.10 )O 3 ]; (abbreviate to (1−x)KNLNTS-xBCTZ) lead-free piezoelectric ceramics were prepared via the solid state combustion technique and the effects of adding BCTZ compound (0≤x≤0.030 wt%) on the phase formation, morphology and electrical behavior of the compound ceramics were investigated. The X-ray diffraction (XRD) results at room temperature of all samples exhibited a single perovskite phase and the BCTZ efficiently diffused into the KNLNTS lattice during the sintering process to produce a solid solution. The crystal structure of these ceramics changed from O+T phases to higher T phase (0≤x≤0.020) and then began to change to a cubic phase when the x content increased from 0.025 to 0.030. A polymorphic phase transition (PPT) of (1−x)KNLNTS-xBCTZ ceramics was observed at an x content of 0.015 and the ratio of the orthorhombic and tetragonal phase was close to equal. Adding BCTZ compound at a ratio ≤ 0.015 promoted better morphology and higher densification. When the BCTZ compound was > 0.015, the microstructure and density of the samples deteriorated. The T O-T and T C of (1−x)KNLNTS-xBCTZ samples reduced continuously with increasing x content. Moreover, the (1−x)KNLNTS-xBCTZ showed a typical relaxor ferroelectric behavior with high BCTZ content. The optimum electrical properties, such as; the highest dielectric behavior (ε r at T r = 2194 and ε m at T C = 6812), excellent ferroelectric properties (P r = 27.9 µC/cm 2 and E C = 9.9 kV/cm) and the highest d 33 (295 pC/N) were obtained by the sample with x content of 0.015 wt%, this sample composition was confirmed to be in the PPT region. The addition BCTZ is a new alternative for improving densification, microstructure, ferroelectric and piezoelectric properties of KNLNTS ceramics. [ABSTRACT FROM AUTHOR]

In this study, the effects of calcination temperature (550–750 °C for 2 h) and sintering temperature (1100–1200 °C for 2 h) on the phase formation, microstructure, electric and magnetic properties of the 0.94Bi 0.5 Na 0.5 TiO 3 -0.06(Ba 0.85 Ca 0.15 )(Ti 0.90 Zr 0.10 ) lead-free piezoelectric ceramic doped with 0.007 mol%Bi 2 FeCrO 6 (BNT-BCTZ-BFCO) were investigated. These ceramics were prepared by the solid state combustion technique using glycine as fuel. The pure perovskite phase was observed in the BNT-BCTZ-BFCO powders attained at the calcined temperature of 650 °C for 2 h. The morphology of the BNT-BCTZ-BFCO powders exhibited an almost-spherical shape and the average particle size increased when the calcination temperature increased from 550 to 750 °C. TEM results of pure BNT-BCTZ-BFCO powder calcined at 650 °C for 2 h showed rounded shapes and the average particle size was ∼ 200 nm. The XRD results of all ceramics exhibited a single perovskite structure with the co-existence of the rhombohedral and tetragonal phases. The average grain size increased with increasing sintered temperature. The density, dielectric constant (ε at T r and T m ) and piezoelectric constant (d 33 ) increased when the sintered temperature increased up to 1150 °C and then reduced in values. At a sintered temperature of 1150 °C, BNT-BCTZ-BFCO ceramic showed the highest relative density (97.2%), maximum dielectric properties (ε at T r = 1783 and ε at T m = 5117), d 33 value (178 pC/N), d * 33 (549 pm/V) and the remnant polarization (P r = 34.66 µC/cm 2 ). At higher sintering temperatures, the properties of BNT-BCTZ-BFCO ceramics decreased due to the evaporation of Bi and Na. All ceramics exhibited the paramagnetic behavior and the magnetization increased with increasing sintering temperature. [ABSTRACT FROM AUTHOR]

Lead free piezoelectric in the ternary system of 0.9BaTiO 3 -(0.1- x )CaTiO 3 - x BaSnO 3 [BCT- x BS], where x = 0.00–0.075, was fabricated via a conventional solid state reaction. The effect of substituting BCT with BS on the crystal structure as well as dielectric, ferroelectric and strain behavior was investigated systematically in order to search for outstanding actuating performances in lead free piezoelectric ceramics. A ferroelectric phase diagram of BT-CT-BS was established in this work, and a multi-ferroelectric phase composition was designed near ambient temperature, based on an established phase diagram. The BS substitute depressed the ferroelectric-paraelectric phase temperature slightly and raised the transition temperatures of O-T phase transformations, thus, the orthorhombic phase could be stabilized above the ambient temperature with x > 0.05. As a result, the polymorphic phase composition showed outstanding piezoelectric values of k p = 41.7%, d 33 = 469 pC/N and d 33 * = 1335 pm/V@10 kV/cm, which are suitable for lead free piezoelectric actuator applications. [ABSTRACT FROM AUTHOR]