Conventional Mixed Oxide Method Research Articles

Effects of Na Excess on the Crystal Structure Ferroelectric and Piezoelectric Properties of (Bi0.487Na0.427K0.06Ba0.026)TiO3 Lead-Free Piezoceramics

In this research, (Bi0.487Na0.427K0.06Ba0.026)TiO3 ceramics were prepared by conventional solid-state mixed-oxide method to incorporate Na excess according to the chemical formula (Bi0.487Na0.427+ x K0.06Ba0.026)TiO3, where x = 0.0, 0.005, 0.010, 0.015 and 0.020. The crystal structure, dielectric, ferroelectric and piezoelectric properties were systematically investigated with respect to the amount of Na excess. X-ray diffraction data identified pure perovskite structure for all compositions. The pseudocubic structure was observed for x = 0.0 − 0.005 before it transformed to rhombohedral structure at x ≥ 0.015. The grain size tended to be larger with increasing Na excess amount. Increasing x also led to a substantial increase in ferroelectric-relaxor transition temperature (T F-R) from 80 °C (x = 0) to 110 °C (x = 0.020). With increasing x from 0 to 0.020, the standard polarization-electric field (P-E) hysteresis measurements revealed a reduction in remanent polarization (P r) together with an increase in coercive field (E c), which was further confirmed by the remanent P-E hysteresis measurements. In addition, the piezoelectric constant (d 33) was also found to steadily decrease as x increased. The observation of increased T F-R and E c along with a decrease in d 33 and P r indicated a stabilization of ferroelectric order induced by Na excess. This research highlights the importance of sufficient control over A-site stoichiometry and how it affects the ferroelectric and piezoelectric properties of BNT-based ceramics.

Enhanced electro-strain with high electrostrictive performances of Bi0.5Na0.4K0.1TiO3 based lead-free piezoelectric ceramics by Ba(Fe0.5Nb0.5)O3

Complex piezoelectric ceramics of (1-x)[0.97(Bi0.5Na0.4K0.1)TiO3–0.03(Ba0.7Sr0.3)TiO3]-xBa(Fe0.5Nb0.5)O3 or (1-x)[0.97BNKT-0.03BST]-xBFN were investigated, where the x value was between 0 and 0.03. All compositions were synthesized via a conventional mixed oxide method. X-ray diffraction and Raman spectroscopy techniques indicated that all ceramics exhibited a coexistence of rhombohedral (R) and tetragonal (T) phases without any impurity phase. However, the T phase became dominant at higher BFN contents. The maximum temperature (Tm), the ferroelectric to ergodic relaxor phase transition temperature (TF-R), and Burn’s temperature (TB) decreased with increasing BFN content, while the dielectric constant at Tm was enhanced for the x = 0.01 ceramic. The BFN additive interrupted ferroelectric ordering, which led to constriction in the hysteresis loops as well as large electric field-induced strains (Smax = 0.42%), a normalized strain coefficient (d*33 = Smax/Emax = 846 pm/V), and an electrostrictive coefficient (Q33 = 0.0432 m4/C2) for the x = 0.01 ceramic under a moderate applied electric field of 50 kV/cm. These results indicated that this ceramic had the potential for electromechanical applications.

Giant dielectric properties of terbium and niobium co-doped TiO2 ceramics driven by intrinsic and extrinsic effects

Giant dielectric properties (GDPs) of complex oxides have been widely investigated because of their potential applications in ceramic capacitors. This study describes the improvement in three crucial factors of the GDPs of TiO2 by co-doping it with Tb and Nb ions. (Tb0.5Nb0.5)xTi1-xO2 (TNTO) ceramics with x = 1–5% were prepared using a conventional mixed-oxide method. The ceramics exhibited a highly compact microstructure and microwave dielectric phases of Tb2Ti2O7 and TbNbTiO6. Notably, the temperature dependence of the dielectric permittivity (ε′) (∆ε′(T)/ε′30℃) was less than | ± 15%| from − 60–210 ℃. Furthermore, the TNTO ceramics exhibited extremely low tanδ values (0.006–0.011) and high ε′ values (4.7–5.3 ×104) at 1 kHz. The tanδ values at 200 °C were particularly low (0.033–0.057). Impedance spectroscopy revealed the presence of semiconducting grains, and the enormous resistivity of the grain boundaries and microwave dielectric phase particles. The GDPs are primarily caused by both intrinsic and extrinsic effects. The intrinsic effect was due to the formation of defect clusters (i.e., Nb25+Ti3+XTi(X=A3+/Ti3+/Ti4+)−Tb23+V0••Ti3+, 2TbTi′−VO••, TbTi′−NbTi•, 3TiTi′−VO••−NbTi•, and TiTi′−VO••−TiTi′), whereas the extrinsic effect resulted from the internal barrier layer capacitor microstructure. The presence of microwave dielectric phases can cause a decrease in tanδ and improve the temperature stability of ε′.

Effective Complex Permittivity of Random Composite Media: PVDF/(Na<sub>1/2</sub>Bi<sub>1/2</sub>)TiO<sub>3</sub>

The present study discusses the fabrication of non-lead ceramic/polymer composites employing (Na1/2Bi1/2)TiO3 (NBT) ceramic powder as a filler and poly(vinylidene fluoride); PVDF as a polymer matrix. The NBT (volume fraction, ϕ = 1) ceramics were synthesized using the conventional mixed-oxide method followed by the high-energy ball milling method whereas (1-ϕ)PVDF/ϕ(Na1/2Bi1/2)TiO3; 0 ≤ ϕ ≤ 0.3 composites were prepared from a melt-mixing process. It was observed that the real and imaginary parts of dielectric permittivity, ac conductivity, and longitudinal piezoelectric charge coefficient increase with the increase in NBT-content. Different dielectric mixing models were presented to determine the effective complex permittivity of the composites. Five dielectric mixture equations have been chosen to test the acceptability of experimental data. It was revealed that theoretical models as given by Bruggman, Rother-Lichtenecker, and modified Rother-Lichtenecker show good agreement with the experimental results of filler-concentration dependent alteration of effective relative permittivity and loss factor of the PVDF/NBT composite. A mathematical model of first-order exponential growth has also been proposed, which fitted excellently the experimental data (r2 > 0.998).

High-Performance Piezoelectric Characteristics of Sm Substituted Pb(Ni,Nb)O3-Pb(Zr,Ti)O3-Pb(Mg,W)O3 System Ceramics for Ultrasonic Transducer Application

In this paper, in order to develop composition ceramics for an acoustic emission sensor application for nondestructive testing, Pb(Ni,Nb2/3)O3-Pb(Zr,Ti)O3-Pb(Mg,W)O3 [PNN-PZT-PMW] system ceramics were manufactured by conventional mixed oxide method using Li2CO3 and CaCO3 as sintering aids. Their microstructural, dielectric and piezoelectric properties were also investigated. At x = 0.0075 Sm, the substituted specimen sintered at 980 (°C), and high values of piezoelectric properties appeared: the dielectric constant (εr) of 2824, piezoelectric coefficient d33 of 630 [pC/N], planar electromechanical coupling factor kp of 0.665, piezoelectric voltage constant g33 of 25.2 [mV.m/N], and high Curie temperature (Tc) = 270 (°C), respectively. These values were applicable for devices such as acoustic emission sensor and ultrasonic transducer.

Effects of Ba(Ti0.90Sn0.10)O3 on Electrical Properties of Bi0.5Na0.5TiO3-0.06BaTiO3 Lead-Free Piezoelectric Ceramic System

Lead-free piezoelectric ceramics with the composition of (1-x)[Bi0.5Na0.5TiO3-0.06BaTiO3]-xBa(Ti0.90Sn0.10)O3 or (1-x)[BNT-0.06BT]-xBTS ternary system (where x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05 mol fraction) have been synthesized by a conventional mixed-oxide method. The optimum sintering condition for all samples was found to be 1125 °C/2 h with a heating/cooling rate of 5 °C/min. The relative densities of all samples were ∼98% with the accompanying linear shrinkage of ∼18%. The XRD patterns of all samples showed no detected impurity phase. It was found that the composition of x = 0.03 exhibited optimum electrical properties (εr = 1895, tan δ = 0.0355 and d33 = 255 pC/N at room temperature), suggesting that this composition had potential to be a promising lead-free piezoelectric candidate compound for dielectric and piezoelectric applications.

Temperature Dependence on Mechanical, Dielectric, and Electric Field-Induced Strain Properties of Lead-Free BNST Ceramics

In this research, temperature dependence on the phase evolution, physical, microstructure, mechanical, dielectric, and electric field-induced strain responses of the Bi0.41Na0.35Sr0.21TiO3 or BNST ceramics were investigated. The BNST ceramic was prepared by a conventional mixed oxide method and sintered at various temperatures from 1100 °C to 1175 °C in order to clarify the optimal sintering temperature for all propereties. X-ray diffraction results showed that all ceramics exhibited a single perovskite without any secondary phases. A mixed between tetragonal and rhombohedral phases were identified for all ceramics. Grain size tended to increase with increasing the sintering temperature. The mechanical improvement was related with the change in densification. The optimum relative density (95.83 %), mechanical (HV = 6.43 GPa, HK = 5.12 GPa, E = 107.57 GPa, and KIC = 2.42 MPa.m1/2), and dielectric properties (ε′ = 1752, tan δ = 0.0514, and δA = 100 K), were obtained for the ceramic sintered at 1125 - 1150 °C. In addition, the obtimum sintering temperature of 1125 - 1150 °C were also found to improve the electric field-induced strain response (Smax = 0.14 % and d*33 = 285 pm/V), and the electrostrictive coefficient (Q33 = 0.0199 m4/C2).

Fe-Doped Barium Lanthanum Titanate as a Competitor to Other Lead-Free Piezoelectric Ceramics.

Multiferroic solid solutions of Ba1−xLaxTi1−x/4O3 and iron (BLFT) were synthesized using the conventional mixed oxide method. The dependence of the piezoelectric coefficients on Fe content in BLFT ceramics was determined by the quasi-static and resonance method. The results indicate that 0.3 mol% addition of Fe3+ ions to the ceramic structure increased the value of the piezoelectric parameter d33 to the maximum of 159 pC/N. This puts BLFT ceramics among other good-quality and lead-free piezoelectric ceramics. A major enhancement of dielectric properties related to the manipulation of Fe content in the barium lanthanum titanate (BLT) ceramics system is reported as well.

Dielectric and Electric Properties of Ba0.996La0.004Ti0.999O3 Ceramics Doped with Europium and Hafnium Ions.

Lanthanum-modified BaTiO3 electroceramic materials have superior dielectric and piezoelectric properties. Ba0.996La0.004Ti0.999O3 (BLT4) seems to be a serious candidate for ultracondensator applications. This manuscript describes the results of hafnium and europium modification of BLT 4 ceramics. The pure and doped ceramic materials were synthesized by the conventional mixed oxide method. The microstructure of obtained samples was examined by scanning electron microscope. The investigations reveal strong correlations between the presence of admixture and the grain size, which was especially visible in the case of the hafnium dopant. The frequency and temperature dielectric characteristics measurements revealed a decrease in electric permittivity. Moreover, the impedance spectroscopy investigations showed severe changes in grains and grain-boundary resistivity, which was connected with changes in electric conductivity.

Enhancement of electrostrictive and magnetic performance with high energy storage efficiency in Fe2O3 nanoparticles-modified Ba(Zr0.07Ti0.93)O3 multiferroic ceramics

Lead-free Ba(Zr0.07Ti0.93)O3/xFe2O3 (93BZT/xFe2O3, x = 0-1.0 mol%) ceramics were prepared using a conventional mixed oxide method. The Fe2O3 nanoparticles additive disturbed the long-range ferroelectric order of the ceramics by changing the normal P-E hysteresis loop for the unmodified ceramic into a constricted loop for the 0.5 mol % Fe2O3 ceramic thereby resulting in an enhancement of the electric field-induced strain and electrostrictive coefficient at this composition. The 1.0 mol% Fe2O3 ceramic showed the highest energy storage efficiency (98%). The M-H hysteresis loop and the magnetocapacitance value were improved by the Fe2O3 nanoparticles additive. Results indicated that the magnetic and electrical performances of Ba(Zr0.07Ti0.93)O3 modified by the Fe2O3 nanoparticle could be remarkably improved, thereby suggesting that this ceramic system has potentials for multifunction device applications.

Investigation of Bi0.5(Na0.80K0.20)0.5TiO3-LiNbO3-Ba(Ti0.90Sn0.10)O3 Lead-Free Piezoelectric Ceramics

The ceramics with the formula of (1-y)[0.995Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3]-yBa(Ti0.90Sn0.10)O3 or (1-y)[0.995BNKT-0.005LN]-yBTS (y = 0-0.05 mol fraction) were successfully prepared by a conventional mixed oxide method. It was found that all compositions showed single phase with a mixed rhombohedral/tetragonal structure. The highest piezoelectric coefficient (d33 = 175 pC/N) with good dielectric (εr = 1775, tanδ = 0.0534) and ferroelectric properties (Pr = 12.33 µC/cm2, Rsq = 1.37) was obtained for y = 0.04 sample. The bipolar S-E loops showed highest Smax = 0.25% at y = 0.05.

Sequential uptake of cadmium and methylene blue from binary solution using zeolite‐TiO2 modified porous CaCu3Ti4O12 photocatalyst

AbstractThis work describes the synthesis of CaCu3Ti4O12 (CCTO) by a facile conventional oxide mixing method. The prepared CCTO particles were further modified with anatase TiO2 NPs (~55 nm size) and zeolite supported TiO2 nanoparticles (NPs) (~58 nm size) for the photocatalytic removal of MB and Cd2+ from the aqueous media under compact fluorescent light. Both nascent and modified CCTO composite materials were characterized using X‐ray diffraction, scanning electron micrograph /energy dispersion X‐ray, BET, UV–VIS‐DRS, and pH of the point of zero charge analyses. These composite materials revealed with remarkable affinity toward MB and Cd2+, whereby the maximum photocatalytic degradation and adsorption capacity reached to 73 and 77 mg/g, respectively. The cations removal efficiencies of the prepared composite materials were found increased in the binary solutions of MB and Cd2+ ions resulting in enhanced degradation and adsorption capacity, qe, up to 132, and 137 mg/g, respectively. The reusability tests revealed that the efficiencies of prepared composites gradually decreased upon reuse.

Dielectric Properties of Modified Lead Zirconate Titanate

In this paper, the dielectric properties of modified i. e. alkali doped lead zirconate titanate Pb(Zr1- xTix)O3 has been studied. The composition Pb1-x (La1-zDz)x (Zry Ti1-y)1-x/4 O3;where x = 0.10, y = 0.70, z = 0.0, 0.1, 0.2, and 0.3, D= Na, K and Li has been prepared by conventional mixed oxide method at a temperature of 11000C. Dielectric constant and dielectric loss measurement of the sintered pellets has been measured. Dielectric measurement shows that the dielectric constant decreases with an increase in temperature. The results show that the dielectric loss is very small and decreases with frequency above 300°C. The increase in the dielectric constant observed at high temperatures and low frequencies is explained in the paraelectric state.

Improvement in Electrical Properties of (Bi0.5Na0.5)TiO3 (BNT) Ceramics Using the Seed-Induced Method

(Bi0.5Na0.5)TiO3 (BNT) lead-free ceramics were prepared by the seed-induced technique using different particle sizes of BaTiO3 (BT) powder as seeds. The BT seeds was synthesized by the molten-salt method and then calcined at different temperatures of 750 (750BTs), 800 (800BTs) and 850 °C (850BTs). The pure perovskite seeds (5 mol%) were mixed with the starting materials of the BNT system for conventional mixed oxide method. After that, the mixture was calcined and sintered at 900 °C for 2 h and 1100 °C for 2 h, respectively. From results it was found that the particle size of BT seed increased with calcine temperature increase from 750 to 850 C. The samples of non-BT seed (S0) and BT seed-added (S1, S2 and S3) showed pure perovskite phase. Average density values were in the range of 5.53-5.77 g/cm3. Dielectric constant (εr) measured at room temperature (at 1 kHz) was in the range of 732.04-788.59. The dielectric loss (tanδ), remnant polarization (Pr) and coercive field (Ec) values decreased with the addition of BT seed. The highest piezoelectric coefficient (d33) ∼156 pC/N was obtained for the sample of 850BTs (S3).

Na1/3Ca1/3Bi1/3Cu3Ti4O12/poly(vinylidene fluoride) composites with high dielectric permittivity and low dielectric loss

Polymer matrix composites of Na1/3Ca1/3Bi1/3Cu3Ti4O12/PVDF with various volume fractions of filler were fabricated. Na1/3Ca1/3Bi1/3Cu3Ti4O12 powders synthesized using a conventional mixed–oxide method were used to incorporate in a PVDF polymer for increasing the dielectric permittivity (ε′). The phase formation and morphologies of the composites were characterized. Na1/3Ca1/3Bi1/3Cu3Ti4O12 particles were found randomly distributed and quite good dispersed in the PVDF polymer. The polar β– and γ–PVDF phases as well as the nonpolar α–PVDF phase were confirmed to exist in the polymer composites. Interestingly, a low loss tangent (tanδ~0.075) and greatly enhanced ε′ ~ 156 with low temperature coefficient (Δε' ~ 8.65%) at 150 °C were obtained in Na1/3Ca1/3Bi1/3Cu3Ti4O12/PVDF composites with 50 vol% filler. Theoretical prediction of the effective ε′ of composites was performed to clarify the origins of the improved dielectric properties. Accordingly, the largely enhanced ε′ resulted from the high–permittivity of Na1/3Ca1/3Bi1/3Cu3Ti4O12 particles used and from interfacial polarization in the composites, while the low value of tanδ was due to the initially low tanδ values of filler ceramics particles.

Influence of Al2O3nanoparticle doping on depolarization temperature, and electrical and energy harvesting properties of lead-free 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3ceramics

In this research article, the effects of Al2O3 nanoparticles (0–1.0 mol%) on the phase formation, microstructure, dielectric, ferroelectric, piezoelectric, electric field-induced strain and energy harvesting properties of the 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (BNT–6BT) ceramic were investigated. All ceramics have been synthesized by a conventional mixed oxide method. The XRD and Raman spectra showed coexisting rhombohedral and tetragonal phases throughout the entire compositional range. An increase of the grain size, TF–R, Tm, εmax and δA values was noticeable when Al2O3 was added. Depolarization temperature (Td), which was determined by the thermally stimulated depolarization current (TSDC), tended to increase with Al2O3 content. The good ferroelectric properties (Pr = 32.64 μC cm−2, Ec = 30.59 kV cm−1) and large low-field d33 (205 pC N−1) values were observed for the 0.1 mol% Al2O3 ceramic. The small Al2O3 additive improved the electric field-induced strain (Smax and ). The 1.0 mol% Al2O3 ceramic had a large piezoelectric voltage coefficient (g33 = 32.6 × 10−3 Vm N−1) and good dielectric properties (εr,max = 6542, Td = 93 °C, TF–R = 108 °C, Tm = 324 °C and δA = 164 K). The highest off-resonance figure of merit (FoM) for energy harvesting of 6.36 pm2 N−1 was also observed for the 1.0 mol% Al2O3 ceramic, which is suggesting that this ceramic has potential to be one of the promising lead-free piezoelectric candidates for further use in energy harvesting applications.

Synergistic effect of terbium and calcium ions on the temperature stability and dielectric loss of BaTiO3-based ceramics

To improve permittivity-temperature stability for BaTiO3 ceramics containing terbium dopant, a new dielectric system (Ba1–xTbx)(Ti1–x/2Cax/2)O3 (x = 0.01–0.20) (BTTC) was prepared at 1400 °C using the conventional mixed-oxide method. The solubility limit of Tb/Ca in BTTC was determined by XRD to be x = 0.12 and BTTC exhibited tetragonal perovskite structures. An abnormal phenomenon was discovered that with increasing x from 0.01 to 0.04 the dielectric peak associated with the orthorhombic-tetragonal phase transition point shifted to low temperatures. The mixed valence states of Tb3+/Tb4+ and mixed A and B occupancy of Tb/Ca2+ in the perovskite lattice were confirmed. BTTC with x = 0.03 and 0.04 satisfied X5R and X4P specifications, respectively, and exhibited some advantageous properties such as higher relative density (ρr = 91 and 93%), lower loss (tan δ = 0.016 and 0.014), higher permittivity (ε′RT = 1820 and 1360), and frequency stability in the range of 1–107 Hz. The point defect chemistry is discussed and the real formula of BTTC is suggested. By comparing BaTiO3 ceramics containing Tb or co-doped with Tb and other rare-earth ions (La, Dy) in many existed works in the dielectric field, the synergistic effect of Tb and Ca in BaTiO3 is more significant and helpful to improve the temperature stability of Tb-related BaTiO3 ceramics or to reduce the dielectric loss in the working temperature region. A small number of B-site Tb4+ in BTTC played a decisive role in the low dielectric loss.

The influence of in situ thermal treatment on electric properties of BaBi2Nb2O9 ceramics

The chemical composition as well as impedance spectroscopy were investigated for BaBi2Nb2O9 ceramics obtained by conventional mixed oxides method, before and after the sample was thermally treated (for 1 h) in an ultra-high vacuum (5 × 10−11 bar) at the temperature of 900 °C. The obtained results indicate the loss of stoichiometry as a result of applied thermal treatment, and lead to conclusion, that the chemical formula of the obtained material should be determined as BaBiNb2O9-x. The suggested formula emphasises the oxygen deficiency due to Bi–O saturated precipitate, along with lack of barium ions at the surface of the sample, and has major influence on material's electric properties.

Excellent electric field-induced strain with high electrostrictive and energy storage performance properties observed in lead-free Bi0.5(Na0.84K0.16)0.5TiO3-Ba(Nb0.01Ti0.99)O3-BiFeO3 ceramics

In this research, ceramics with a high electromechanical strain based on the composition (1-x)[0.97Bi0.5(Na0.84K0.16)0.5TiO3-0.03Ba(Ti0.99Nb0.01)O3]-xBiFeO3 or (1-x)[BNKT-0.03BNbT]-xBFO (with x = 0, 0.03, 0.05, 0.07, and 0.09 mol fraction) were investigated. All compositions were synthesized via a conventional solid-state mixed oxide method. The effects of the addition of BFO on the phase structure, dielectric, ferroelectric, and piezoelectric properties and electric field-induced strains behavior of BNKT-0.03BNbT ceramics were systematically studied in this work. X-ray diffraction (XRD) analysis revealed that all ceramics exhibited a pure perovskite structure. The coexistence of rhombohedral (R) and tetragonal (T) phases was observed for all compositions. The electric field-induced strain increased with increasing BFO content and attained a maximum value of Smax = 0.65% and d*33 = 1161 pm/V (@40 kV) for the composition x = 0.05 at room temperature (RT). The bipolar strain behavior exhibited minimal asymmetry and a low driving electric field. The composition also exhibited a high electrostrictive response (Q33 ∼ 0.039 m4/C2). In addition, the x = 0.09 composition showed excellent energy storage properties, with an energy storage density of 0.91 J/cm3 at 125 °C, high normalized energy storage density (∼0.14 μC/mm2), thermal stability (7% for 75-150 °C) and energy storage efficiency (η = 87% @125 °C). These results suggest that the (1-x)[BNKT-0.03BNbT]-xBFO ceramics are promising as lead-free piezoelectric material candidates, and are also suitable for both actuator and high temperature energy storage applications.

Effect of WO3 loading on structural, electrical and dielectric properties of CaCu3Ti4O12 ceramic composites

CaCu3Ti4O12–xWO3 (CCTO–xWO3) (x = 5, 10, 15, 20 wt%) ceramic composites were synthesized using conventional mixed oxide method. The effect of various amounts of WO3 loading on its microstructure, electrical and dielectric properties of CCTO ceramic composites were studied using XRD, FESEM-EDAX, Hall effect and dielectric measurement. XRD analysis revealed that the CCTO–xWO3 ceramic composites have cubic structure and WO3 loading had no effect on its crystal phase structure. The FESEM analyses showed that the samples had a porous structure. It is noted that the porosity of CCTO films increased from 2.97% to 6.11% with 20% wt. WO3 loading. Also, the electrical resistivity and dielectric permittivity of CCTO ceramics was reduced with increasing WO3 loading. Particularly, the CCTO–20 wt% WO3 ceramic composites exhibited the lowest electrical resistivity (81 Ω cm) and dielectric permittivity (486 measured at 1 kHz) but the highest dielectric loss (0.6 measured at 1 kHz). These results have practical implication for fabrication and optimizing of CCTO ceramics for low power loss microelectronics.