Conventional Solid-state Reaction Sintering Research Articles

Electrocaloric effect, pyroelectric response and energy storage performance of lanthanum-modified PZT relaxor ferroelectric ceramic

Pb0·85La0·10Zr0·60Ti0·40O3 ferroelectric ceramic system was synthesized via the conventional solid-state reaction sintering route. A systematic study on the pyroelectric response, electrocaloric effect and energy storage properties has been carried out in a wide temperature range, in order to explore its multifunctional features. The obtained results from X-ray diffraction technique, performed at room temperature, revealed the coexistence of two ferroelectric phases governed by the tetragonal (P4mm) and monoclinic (C1m1) symmetries. The pyroelectric behavior of the studied sample has been analyzed by the static method, from the temperature dependence of the pyroelectric current. The electrocaloric response as well as the energy storage performance have been investigated from the ferroelectric hysteresis loops (P−E curves), at 50 kV/cm, covering a wide temperature range. The obtained results revealed a ferroelectric ceramic composition with suitable properties and strong potential to be used in multifunctional electronic devices based on pyroelectric sensors combined with high efficiency energy storage performance and solid-state refrigeration technologies.

Figures of merit of PLZT ferroelectric ceramics for practical applications

Structural, microstructural and pyroelectric properties were investigated in PZT-based ferroelectric ceramics for a composition close to the morphotropic phase boundary (Zr/Ti = 53/47), as a function of the lanthanum content. The samples were prepared via the conventional solid-state reaction sintering method. Three compositions were synthetized and studied following the PbZr0.53Ti0.47O3 + x mole% La nominal formula, where x = 0.0, 2.5 and 5.0. The structural characterization confirmed the presence of both tetragonal and rhombohedral phases for all the studied compositions, showing a decrease in the tetragonality factor (c/a) with the increase of the lanthanum concentration. The observed decrease in the stability of the ferroelectric phase (in favor of the paraelectric one) have been discussed in light of the solubility of the doping cation into the studied PZT perovskite structure. Microstructural properties revealed low pores concentration micrographs, showing homogeneous microstructures and uniform grain-sizes. The pyroelectric response of the as-prepared PLZT samples was also investigated in a wide temperature interval. The lower lanthanum content composition exhibited the best properties, characterized by a high pyroelectric coefficient and enhanced figures of merit. These characteristics make such a composition a promising material for practical applications.

Structural, microstructural and dielectric characterizations of (Bi0.5Na0.5)TiO3based lead-free ferroelectric ceramics

(1–[Formula: see text][Formula: see text][Formula: see text]TiO3–[Formula: see text]BaTiO3lead-free ceramics have been obtained from the conventional solid-state reaction sintering method. The structural properties were investigated from X-ray diffraction and Raman spectroscopy techniques. Results revealed well-crystallized ceramic samples with perovskite structure. Microstructural properties, obtained from scanning electron microscopy measurements, have shown high density with very low porosity level. The dielectric response, analyzed as a function of the temperature and several frequencies, showed very broad peaks with a strong frequency dependence of the temperature for the maximum dielectric permittivity for the modified system. Results were analyzed considering the influence of the BaTiO3 content on the studied physical properties.

Dielectric properties and electrocaloric effect of yttrium-modified BaTiO3 ceramics

The electrocaloric effect (ECE) is a promising candidate to replace the vapor-compression cooling technology, which has reached its end of improving the energy utilization efficiency. In the present work, the Y-modified BaTiO3 ceramics with nominal compositions of Ba(Ti1-xYx)O3 (abbreviated as BT-100xY, where x = 0.0125, 0.025, 0.0375, 0.050 and 0.0625) have been prepared through the conventional solid-state reaction sintering method. The dielectric properties and electrocaloric effect of BT-100xY ceramics have been investigated in detail. The XRD patterns indicate that all the BT-100xY ceramics possess pure perovskite structure without secondary phases. The temperature dependence of dielectric permittivity reveals that the BT-1.25Y, 2.5Y, 3.75Y and 5.0Y are normal ferroelectrics, and the BT-6.25Y is a relaxor ferroelectric. The ECE is calculated through the indirect equation based on Maxwell relation. The BT-2.5Y exhibits the largest ΔT = 1.26 K and the largest ΔS = 1.68 J/kg · K among all the BT-100xY ceramics, and the BT-2.5Y also exhibits the largest ΔT/ΔE = 0.296 × 10−6 K · m/V and the largest ΔS/ΔE = 0.394 × 10−6 J · m/kg · K∙V. The ECE in our work is comparable with or even larger than that of BaTiO3-based ceramics previously reported, which indicates that the BT-100xY ceramics are promising ECE materials.

Effects of non-stoichiometry on the microstructure and microwave dielectric properties of Ba1+xCu2V2O8 (x = 0.15, 0.25, 0.35) ceramics

The Ba1+xCu2V2O8 (x = 0.15, 0.25, 0.35) ceramics were synthesized using the conventional solid-state reaction sintering method. The effects of the non-stoichiometry on the crystalline phases, densification sintering, microtopography, and microwave dielectric properties of the Ba1+xCu2V2O8 (x = 0.15, 0.25, 0.35) ceramics were studied. In the sample (x = 1) prepared according to the stoichiometry, only the single crystalline phase of BaCu2V2O8 existed. The excess of Ba2+ ions directly led to the precipitation of a new Ba2V2O7 phase. The detection of element composition using EDS also confirmed the results of the phase composition. The SEM results indicated that the microstructure of the ceramics became loose with the increase of Ba2+ ion content. The theoretical microwave dielectric properties were calculated according to the general formula of compounds. The results of the calculation showed that the precipitation of the Ba2V2O7 phase was the main factor affecting the microwave dielectric properties of the ceramics. The measured results of microwave dielectric properties were consistent with the calculated results. The microwave dielectric properties of the Ba1.35Cu2V2O8 sample calcined at 725 °C for 6 h were shown as follow: er = 12.25, Qf = 46,320 GHz, τf = − 35.3 ppm/°C.

Role of A- and B-site excess doping on the improvement of the piezoelectric properties of BaTiO3 lead-free piezoceramics

Excess Li, Al, and Si co-doped BaTiO3 (BT) piezoceramics were synthesized using a conventional solid-state reaction sintering method. The influences of excess A- and B-site doping on the crystalline structure, dielectric, ferroelectric, and piezoelectric properties of BT ceramics were studied and discussed. While ceramics had a tetragonal crystal structure, weak secondary phases appeared with an increase in the doping content. Compared to pure BT ceramics, the dielectric constant of the Li/Al/Si-doped ceramics decreased, but the dielectric loss decreased and remained at a relatively low level of approximately 0.017 with a Li–Al content of x and 0.02 with an excess Si doping content of Δ. The remnant polarization 2Pr reached the maximum values of 12.55 μC/cm2 at x = 0.07 for excess Li–Al doped ceramics and 18.58 μC/cm2 at Δ = 1.6% for excess Si doped ceramics. The piezoelectric constant d33 was significantly improved owing to the excess doping of Li–Al and Si without decreasing the Curie temperature, and its maximum value was approximately 212 pC/N at x = 0.032. The excess Si doping at the B-site helped to improve and stabilize the piezoelectric properties of the ceramics in a wide excess composition range.

Effects of BiScO3 Doping on the Phase Structure, Ferroelectric, Energy Storage, Strain, and Dielectric Properties of Bi0.5Na0.5TiO3 Ceramics

In this study, (1–x)Bi0.5Na0.5TiO3– xBiScO3 (BNT–xBS) ceramics were synthesized via conventional solidstate reaction sintering. The effects of the BiScO3 content on the surface microstructure, energy storage, strain, and dielectric properties of BNT–xBS ceramics were systemically investigated. Results indicated that the phase structure of BNT–xBS ceramics transformed from the rhombohedral phase into the pseudo-cubic phase. As the increasing BiScO3 content, the average grain size decreased. BiScO3 destroyed the long-range ordered ferroelectric phase, enhancing relaxor behavior. Energy storage density initially increased and then decreased, reaching a maximum of 0.17 J/cm3 at x = 0.1. In addition, the maximum energy storage efficiency was 59% at x = 0.2. The BiScO3 content significantly affected the electrical properties of BNT– xBS ceramics.

Fabrication, microstructure and optical properties of large-sized Nd:YAG and composite Yb:YAG transparent ceramic slabs

Abstract Large-sized Nd:YAG and composite Yb:YAG transparent ceramic slabs of high quality were fabricated by the conventional solid-state reaction sintering technique. The Yb:YAG transparent ceramic slabs were surrounded by undoped YAG transparent ceramics and this composite structure was built in the process of ceramic shaping. The difference in microstructure between Yb:YAG and YAG transparent ceramics was not observed and the composite Yb:YAG slabs showed fully dense and pore-free microstructure. The in-line transmittances at 400 nm reached 81.7% and 79.7 % for YAG and Yb:YAG transparent ceramics, respectively, indicating good optical quality of the composite ceramic slab. And the optical transmission micrograph was very homogeneous with only a few isolated scattering centers. These results suggested that building composite structure in the process of ceramic shaping was a simple and reliable technical scheme. Moreover, the large-sized Nd:YAG transparent ceramic slab with size of 150.0 mm × 50.0 mm × 4.0 mm was also prepared. The calculated absorption coefficient was about 0.002 cm-1 @1064 nm, which suggested that the optical quality of this Nd:YAG transparent ceramic slab had reached the level of Nd:YAG crystals.

Design development of (Ba1-xCax)(Ti1-ySny)O3 lead-free piezo ceramic by two manufacturing methods of CSS and SPS, promising for delamination damage detection

Delamination in laminated composite structures plays a major role in decreasing structural strength and stiffness, consequently downgrading system integrity and reliability. Therefore, the delamination detection by the method of sending and receiving propagated wave with piezoelectric sensors is very important. In order to detect the structural damage using piezo ceramics sensors with a high piezoelectric coefficient (d33), a lead-free piezo ceramic (B1-xCxT1-ySy)O3 or (Ba1-xCax)(Ti1-ySny)O3 was designed and manufactured by two methods of conventional solid-state reaction sintering (CSS) and spark plasma sintering (SPS). The electrical and electromechanical properties, X-ray diffraction analysis, thermal analysis (DSC) and scanning electron microscopy (SEM) were investigated on the samples and the samples properties were compared with different contents of Ca and Sn dopants. (Ba1-xCax)(Ti1-ySny)O3 (x = 0.05, 0.1 mole% and y = 0.02–0.12 mole %) ceramics with a high relative density over 97.02 (±0.2)% were prepared by CSS method at 1480 °C. A polymorphic phase transition from orthorhombic phase to tetragonal phase was confirmed in the composition range of x = 0.05, 0.1 and 0.02 ≤ y ≤ 0.12 by XRD analysis that was measured at room temperature. In CSS method a high piezoelectric coefficient (d33) up to 605 pC/N was obtained for x = 0.05 mole% and y = 0.09 mole%, which was higher than the other previously reported components of B1-xCxT1-ySy system. The corresponding planar electromechanical coupling factor (kp) and inversed piezoelectric coefficient (dS/dE) reached to 42.8% and 1203 pm/V, respectively. For the prepared SPS samples at 1330 °C and under the pressure of 55 MPa, the corresponding d33, kp, tanδ and dS/dE were 752 pC/N, 54.2%, 2.7% and 1248 pm/V, respectively. The average relative density of SPSed samples of the same composition reached to 99.50 (±0.2)%. It seems that designing and forming a suitable phase boundary starting from a tricritical triple point in the MPB zone that along with SPS manufacturing method could enhance and develop high-performance Pb-free piezoelectrics.

Structure, dielectric, ferroelectric, and field-induced strain response properties of (Mg1/3Nb2/3)4+ complex-ion modified Bi0.5(Na0.82K0.18)0.5TiO3 lead-free ceramics

In this work, Bi0.5(Na0.82K0.18)0.5Ti1–x(Mg1/3Nb2/3)xO3 (BNKT–xMN) lead-free ceramics with x = 0.02–0.045 were fabricated by conventional solid state reaction sintering method. The effects of MN content on the phase structure, microstructure, dielectric, ferroelectric, energy storage and strain response were investigated. The MN diffuses into the lattice of BNKT matrix and forms solid solution. The MN doping pinches the hysteresis loops, and improves the energy storage density and efficiency. Meanwhile, the electric field-induced strain response with low hysteresis is also promoted. The B-site modification induces the transition from ferroelectric phase to ergodic relaxor. The significant enhancement in energy storage and strain response is attributed to the compositionally induced phase transition. A noticeable diffuse phase transition is confirmed by dielectric analysis. Thus, the energy storage and strain properties of BNKT ceramics can be modified by complex-ion induced phase transition.

Effects of La Doping on Microstructure and Ferroelectric Properties of BLTN Lead-Free Ceramics

Lead-free EO ceramics have been received increasing attentions from the view point of green environment in recent years. In this study, lead-free Ba6-1.5xLaxTi2Nb8O30 (0≤x≤7%) ceramics were synthesized by the conventional solid state reaction sintering method. The effects of lanthanum doping on the microstructure and electrical properties of Ba6Ti2Nb8O30 (BTN) ceramics were investigated and analyzed. The XRD results revealed that the lanthanum doping changed the BTN lattice parameters slightly. The sample grain size, dielectric constants (1kHz) and the temperature Tm gradually decreased with the increasing of lanthanum doped content. The optimized BLTN ceramic sample with x=4 mol % exhibited a good transparency and excellent electrical properties (Ps=6.41 μC/cm2, Pr=0.77 μC/cm2, and Ec=3.80 kV/cm).

Effect of spark plasma sintering (SPS) on the thermoelectric properties of magnesium ferrite

Magnesium ferrite MgFe2O4 was synthesized with two different methods, spark plasma sintering (SPS) and conventional solid-state reaction sintering (SSRS), and thermoelectric properties were investigated. SPS processing was found to yield two attractive features: SPS at 900 °C enabled retaining the submicron particle size of 0.3–0.5 µm from ball-milling, leading to lower thermal conductivity, 3 W/mK@300 K. 1200 °C SPS sintering led to the same sample grain size of 1.0–3.0 µm as SSRS, but still exhibited significantly lower thermal conductivity of 4.3 W/mK@300 K compared to the SSRS sample with 14 W/mK@300 K, which exhibited neck formation between particles. Furthermore, while the finer microstructuring led to a reduction in the thermal conductivity, the resistivity of SPS MgFe2O4 showed little dependence on the particle size at expected thermoelectric working temperatures above 523 K, which indicates success to some degree of phonon selective scattering due to differences in mean-free-paths of electrons and phonons. As a process, SPS samples are found to exhibit four- to sevenfold enhancement of ZT compared to the conventional SSRS sample. While the maximum ZT in the present samples is relatively low, taking a value of 0.07 for the SPS 1200 °C sintered sample, the processing insights may be utilized for similar systems.

Large strain response in (Mn,Sb)–modified (Bi0.5Na0.5)0.935Ba0.065TiO3 lead–free piezoelectric ceramics

Lead–free piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1–x(Mn0.5Sb0.5)xO3 (BNBT6.5–xMS, x=0.005, 0.010, 0.015, 0.020) were prepared by conventional solid state reaction sintering technique. All ceramics present a pure perovskite phase structure, indicating that (Mn, Sb) has completely diffused into the BNBT6.5 lattice in the studied components. The addition of (Mn, Sb) disrupted the ferroelectric long–range order and promoted the electric field induced strain response. At x=0.015, a large electric field–induced unipolar strain of 0.48% (at an applied electric field of 80kV/cm) with normalized strain d33*(Smax/Emax) of 602pm/V are achieved. Temperature dependent measurements of both polarization and strain from room temperature to 120°C were also studied, and the results suggest that the origin of the large strain is due to a reversible field–induced non–polar relaxor phase to polar ferroelectric phase transformation.

KNN–NTK composite lead-free piezoelectric ceramic

A (K,Na)NbO3-based lead-free piezoelectric ceramic was successfully densified. It exhibited an enhanced electromechanical coupling factor of kp = 0.52, a piezoelectric constant d33 = 252 pC/N, and a frequency constant Np = 3170 Hz m because of the incorporation of an elaborate secondary phase composed primarily of KTiNbO5. The ceramic's nominal composition was 0.92K0.42Na0.44Ca0.04Li0.02Nb0.85O3–0.047K0.85Ti0.85Nb1.15O5–0.023BaZrO3–0.0017Co3O4–0.002Fe2O3–0.005ZnO, abbreviated herein as KNN–NTK composite. The KNN–NTK ceramic exhibited a dense microstructure with few microvoids which significantly degraded its piezoelectric properties. Elemental maps recorded using transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM–EDS) revealed regions of high concentrations of Co and Zn inside the NTK phase. In addition, X-ray diffraction patterns confirmed that a small portion of the NTK phase was converted into K2(Ti,Nb,Co,Zn)6O13 or CoZnTiO4 by a possible reaction between Co and Zn solutes and the NTK phase during a programmed sintering schedule. TEM studies also clarified a distortion around the KNN/NTK interfaces. Such an NTK phase filled voids between KNN particles, resulting in an improved chemical stability of the KNN ceramic. The manufacturing process was subsequently scaled to 100 kg per batch for granulated ceramic powder using a spray-drying technique. The properties of the KNN–NTK composite ceramic produced using the scaled-up method were confirmed to be identical to those of the ceramic prepared by conventional solid-state reaction sintering. Consequently, slight changes in the NTK phase composition and the distortion around the KNN/NTK interfaces affected the KNN–NTK composite ceramic's piezoelectric characteristics.

Large piezoelectric properties induced by doping ionic pairs in BaTiO3 ceramics

The high piezoelectric properties of piezoelectric ceramics are typically obtained by inducing a phase transition between two ferroelectric phases, using either the morphotropic phase boundary (MPB) or the polymorphic phase transition (PPT). Here we demonstrate that neither the MPB nor the PPT is necessary to achieve high piezoelectric properties. Our results show that the optimized distribution of Li+–Al3+ pairs parallel to the [001] direction, as found in our xLiAlSiO4/BaTiO3 (xLAS/BT) lead-free piezoelectric ceramic system prepared from ordinary raw materials by conventional solid-state reaction sintering, can generate a large piezoelectric constant (d33) of 378pC/N when x=7.5mol.%. The d33 value of the 7.5mol.% LAS/BT ceramic is more than three times that of the pure BT ceramic. The distortion connected to the proposed Li+–Al3+ pairs locally creates unit cells of less than tetragonal symmetry, and these low-symmetry cells can be responsible for the high piezoelectric response. The high-temperature stability testing reveals that these doped ceramics are usable at temperatures as high as 120°C. This piezoelectric mechanism coming from the doping ionic pairs provides a new method to achieve large piezoelectric properties in a wide range of ABO3-type perovskite systems.

Enhanced piezoelectric and mechanical properties of AlN-modified BaTiO3 composite ceramics.

BaTiO3-xAlN (BT-xAlN) composite ceramics were prepared by conventional solid state reaction sintering. The effects of the AlN content on the crystalline structures, densities, and electrical and mechanical properties of the BT ceramics were investigated. The BT-1.5%AlN ceramic exhibits a good piezoelectric constant of 305 pC N(-1) and an improved Vickers hardness of 5.9 GPa. The enhanced piezoelectricity originates from interactions between defect dipoles and spontaneous polarization inside the domains due to the occurrence of local symmetry, caused by the preferential distribution of the Al(3+)-N(3-) pairs vertical to the c axis. The hardening of the material is attributed to the improved density, and particle and grain boundary strengthening. Our work indicates that if a suitable doping ion pair is designed, lead-free ceramic systems prepared from ordinary raw materials by a conventional sintering method have a high probability of exhibiting good piezoelectric and mechanical properties simultaneously.

Manganese doping effects on interband electronic transitions, lattice vibrations, and dielectric functions of perovskite-type Ba0.4Sr0.6TiO3 ferroelectric ceramics

The Ba0.4Sr0.6−x Mn x TiO3 (BSMT) ceramics with different Mn composition (from 1% to 10%) have been prepared via the conventional solid-state reaction sintering. The X-ray diffraction analysis shows that the ceramics are polycrystalline with the single perovskite phase. The lattice vibrations and optical properties have been investigated using Raman scattering, spectroscopic ellipsometry (SE), and infrared reflectance spectra. It was found that the optical bandgap for the BSMT ceramics is varied between 3.40 and 3.65 eV. The three first-order Raman-active phonon modes can be observed, and the frequency of the A 1(LO3)/E(LO) mode shows a blue shift of 8 cm−1 with the Mn composition, which can be attributed to the distortion of the TiO6 octahedron. With increasing Mn composition, the frequency of the infrared-active TO4 mode decreases from 532 to 520 cm−1, owing to the local variation of the lattice constant induced by the Mn incorporation. Moreover, the optical functions of the ceramics from the far-infrared to ultraviolet region are obtained based on the SE and reflectance spectra, which is useful for the potential applications in ferroelectric-based optoelectronic devices.

Dielectric and piezoelectric properties of SrBi 4− xHo xTi 4O 15 ( x=0.00, 0.02, 0.04 and 0.06) ceramics

The dielectric and piezoelectric properties of SrBi 4− x Ho x Ti 4O 15 ( x=0.00, 0.02, 0.04 and 0.06) ceramics were investigated. SrBi 4− x Ho x Ti 4O 15 ( x=0.00, 0.02, 0.04 and 0.06; SBHT- x) ceramics were synthesized by the conventional solid state reaction sintering method. An X-ray diffraction measurement indicated that a single phase layered perovskite was obtained for all compositions. Studies of dielectric properties with temperature at different frequencies and piezoelectric properties have been carried out.

Piezoelectric and ferroelectric properties of SrBi 2(Nb 1− χTa χ) 2O 9 ceramics

SrBi 2(Nb 1− χ Ta χ ) 2O 9 (0 ≤ χ ≤ 1.0) bismuth layered structured ferroelectric (BLSF) ceramics were prepared by the conventional solid-state reaction sintering method. XRD analysis indicated that a single phase of SrBi 2(Nb 1− χ Ta χ ) 2O 9 was formed for all compositions. The substitution of Ta for Nb decreases Curie temperature ( T c), maximum permittivity ( ɛ m), remnant polarization ( P r) and coercive field ( E c), whereas temperature coefficient of resonance frequency (TCF) increases with the increase in Ta content for SrBi 2(Nb 1− χ Ta χ ) 2O 9. All of compositions have a low permittivity ( ɛ r), a low electromechamical coupling coefficient ( K p) and a high mechanical quality factor ( Q m), which are advantageous to be used in piezoelectric resonator device.