Densities Of Ceramics Research Articles

Machine learning optimization for a novel process of acid-base chemical densification of BaZrO3 ceramics

Low-temperature ceramic fabrication techniques, which can reduce CO2 emissions and energy consumption, are important. BaZrO3 ceramics, which are conventionally sintered at over 1600 °C, were prepared at close to room temperature by a novel process called acid-base chemical densification (ABCD). BaZrO3 ceramics could be fabricated by reacting a compact of ZrO2 hydrous gel with a solution of Ba(OH)2·8H2O at less than 100 °C. The densities of BaZrO3 ceramics depended on the various ABCD process parameters. To obtain a higher density of BaZrO3 ceramics, all the parameters were optimized simultaneously using machine learning. Three algorithms, Linear Regressor (LR), Random Forest (RF) regressor, and Light Gradient Boost Machine (LGBM), were compared for the prediction of BaZrO3 density. The RF regressor predicted the relative densities of BaZrO3 ceramics using the process parameters with high accuracy. From the results of the important features obtained from the RF model, the water content in the zirconia hydrous gel used as a precursor is important for the densification of BaZrO3 in this process, although the reaction time and precursor density affected the densities in the ABCD process. In contrast, varying the reaction temperature in the chemical reaction between ZrO2 hydrous gel and Ba(OH)2·8H2O did not effectively improve the density in this study. By analyzing the top six important features in the RF model, we attempted to improve the accuracy of density prediction using the LR to predict the densities from the extrapolation data. Using an improved LR model, it was found that reducing the water content in the precursors is important for obtaining dense BaZrO3 ceramics by the ABCD process. The water in the gel disturbs the densification because the volume of water molecules remains as pores in the pellets.

Improvement of nuclear photon and neutron shielding performance of Tm2O3 and Dy2O3 doped ceramics: An experimental study

In this study, 60KAlSi3O8+10Al2Si2O5(OH)4+(30-x)SiO2+xA2O3 (x = 0, 10, 20, 30 wt% and A = Tm, Dy) ceramics were produced by conventional method to determine their usability as shielding material against ionized gamma radiation. To investigate the ionized photon shielding properties of the fabricated materials, the photon intensities (I and I0) were experimentally measured at 81, 160, 223, 302, 356, and 383 keV energies emitted from 133Barium radioisotope, and then the mass attenuation coefficient (μρ), The linear attenuation coefficients (μ, cm−1), half-value thickness (Δ0.5), mean free path (λ), effective atomic numbers (Zeff) and electron densities (Nel) were derived experimentally. The obtained results were benchmarked with the calculated values from the EpiXS program. Also equivalent absorbed dose (EAD) values for fast neutrons were measured using BF3 gas proportional neutron detector from the Canberra NP-100B series and a241Am/Be neutron source with a 10 mCi activity. In addition, fast neutron shielding parameters (ΣR) of ceramics were also computed theoretically. The density of the fabricated ceramics varied from 2.607 g/cm3 to 4.392 g/cm3 when the Tm2O3 was raised from 0 wt% to 30 wt%. Likewise, with the addition of Dy2O3 compound, the densities of ceramics varied between 2.607 g/cm3 to 4.152 g/cm3. It was found that nuclear radiation shielding properties evolved by adding Tm2O3 and Dy2O3 compounds in the present ceramic.

Role of TiO2 addition on recycling of TV screen waste glasses: Experimental and theoretical studies on structure and radiation attenuation properties

Using the powder metallurgy, TiO2-doped TV screen glass ceramic samples were prepared with TiO2 concentrations of 0 (S-TV), 10 (S-TV/Ti10), and 20 (S-TV/Ti20) wt%. The TV screen glass was collected from a damaged TV's CRT. The fabricated materials were investigated for their physical, structural, and radiation-shielding attributes. The chemical composition of the prepared glasses was analysed with the aid of the X-ray fluorescence (XRF) method. The crystalline phase and microstructure of the glass ceramics were studied through the X-ray diffraction (XRD) method and scanning electron microscope (SEM), respectively. The density and Vickers hardness of the sample were determined by the Archimedes method and a micro hardness tester, respectively. The absorption parameters of electrons, protons, alpha particles, carbon ions, fast neutrons, and thermal neutron were calculated from various software and analytic expressions. The XRD spectra of the samples showed the presence of distinct crystalline peaks associated with TiO2, SiO2, and Ba2SiO4. The SEM images revealed that crystalline structures nucleated and increased with coarser crystalline grains when the amount of TiO2 was increased. The densities of the glass ceramics were 2.525, 2.546, and 2.285 g/cm3 for the S-TV, S-TV/Ti10, and S-TV/Ti20 samples, respectively while the corresponding Vickers hardness values were 495, 540, and 578 HV. The projected range of electrons, protons, alpha particles, and heavy carbon ions were within the limits 2.78–32182.18 μm, 0.215–1400 μm, 0.154–130.54 μm, and 0.053–14.10 μm in S-TV, 2.76–31991.36 μm, 0.205–1320 μm, 0.147–122.05 μm, and 0.049–13.11 μm in S-TV/Ti10, and 2.84–32824.95 μm, 0.212–1360 μm, 0.151–125.55 μm, and 0.051–13.45 μm in S-TV/Ti20, respectively. Among the three samples, S-TV was the best thermal neutron absorber, while S-TV/Ti10 is most effective in slowing down fast neutrons. The optimum TiO2 doping content for enhancing the charged particle and fast neutron moderating abilities of TV screens is 10 wt%.

Fabrication, microstructure, dielectric, and ferroelectric properties of (Bi0.5Na0.5)0.94Ba0.06TiO3 nanograined ceramics via cold-sintering-assisted sintering

(Bi0.5Na0.5)0.94Ba0.06TiO3 nanograined ferroelectric ceramics were successfully fabricated via a simple cold-sintering-assisted sintering method. Here, the cold-sintering-assisted sintering method includes two steps, i.e., cold-sintering and post-annealing. The cold-sintered samples were prepared via moistening (Bi0.5Na0.5)0.94Ba0.06TiO3 powders with de-ionized water followed by compressing under various pressures at 180 °C, which exhibit densities as high as 83.7% ∼ 93.6% of the theoretical value. Effects of cold-sintering time and pressure on densification and microstructure of the cold-sintered samples were studied. The cold-sintered samples were then annealed at 800 °C–900 °C, which are far below the temperatures for sintering (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics via the conventional solid-state reaction method. After being annealed, the relative densities of the post-annealed ceramics are all higher than 96%. The dielectric and ferroelectric behaviors of the post-annealed ceramics were compared with those of the ceramics with the same composition and various mean grain sizes. The cold-sintering-assisted sintering mechanism was discussed based on the transmission electron microscopy measurement. The study provides a simple and efficient cold-sintering-assisted sintering method for obtaining dense (Bi0.5Na0.5)0.94Ba0.06TiO3 nanograined ferroelectric ceramics at relatively low temperatures with excellent dielectric and ferroelectric properties.

Neodymium and samarium codoped PLZT ferroelectric ceramics for potential betavoltaic nuclear batteries

In this work, neodymium (Nd) and samarium (Sm) codoped lead lanthanum zirconate titanate (PLZT) ceramics were prepared by a high-temperature solid-state method. The samples were characterized by X-ray diffraction, scanning electron microscopy and ferroelectric analysis. Rare earth-doped PLZT ceramics show good phase formation. An appropriate rare earth element doping amount increases the densities of PLZT ceramics and reduces their resistivities, which is due to the role of rare earth elements in grain refinement. However, the increase in the amount of grain boundaries caused by grain refinement also affects domain inversion. Therefore, with increasing doping concentration, the remnant polarization of PLZT gradually decreases, and the doping of rare earth elements also slightly reduces the band gap of PLZT. Under irradiation with an X-ray simulated beta source with a particle energy of 10 keV (between the average energies of the beta particles of 3H and 63Ni), the ceramic sheets in this work produce current densities of up to 1.38 nA/cm2. This indicates that Nd and Sm codoped PLZT ceramics have a certain potential for application in betavoltaic batteries.

Effect of Different Ca2+ and Zr4+ Contents on Microstructure and Electrical Properties of (Ba,Ca)(Zr,Ti)O3 Lead-Free Piezoelectric Ceramics

In the preparation of (Ba,Ca)(Zr,Ti)O3 lead-free piezoelectric ceramics, different Ca2+ and Zr4+ contents will greatly affect the phase structure, microstructure, and electrical properties of the ceramics. XRD shows that all samples have pure perovskite phase structure, and the (Ba0.85Ca0.15)(ZryTi1−y)O3 ceramics morphotropic phase boundary region from tetragonal phase to rhombohedral phase near 0.08 ≤ y ≤ 0.1. From the dielectric temperature curve, the phase transition temperature (TO-T) was found near room temperature at 0.12 ≤ x ≤ 0.18 for the (Ba1−xCax)(Zr0.1Ti0.9)O3 ceramics. Both Ca2+ and Zr4+ increase have a significant decrease on the Curie temperature Tc. All samples were revealed as relaxers with diffusivities in the range 1.29 ≤ γ ≤ 1.82. Different from the undoped ceramics, ceramics doped with Ca and Zr ions exhibit saturated P–E hysteresis loops, and their ferroelectric properties are significantly optimized. In particular, the (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramic demonstrated optimal properties, namely d33 = 330 pC/N, kp = 0.41, εr = 4069, Pr = 4.8 μC/cm2, and Ec = 3.1 kV/cm, indicating that it is a viable lead-free piezoelectric contender. Variations in Ca and Zr content have a significant effect on the crystal grain sizes and densities of ceramics, which is strongly associated with their piezoelectricity.

Synthesis of BaTiO<sub>3</sub> Ceramics Using Co-Precipitation and Solid-State Reaction Method with Sintering Temperature Variation

Barium Titanate (BT) is one of the most intriguing ferroelectric materials widely exploited both for academic and technological utilization. The study aimed to investigate characteristics of BT ceramics Synthesized by co-precipitation (BT-C) and solid-state methods (BT-S) with variation of sintering temperatures. Here, the sintering temperatures are 900°C, 1000°C, 1100°C, and 1200°C for 4 h of each The characteristics are microstructure, morphology, and dielectric properties evaluated using X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), and Inductance-Capacitance-Resistance (LCR) meter, respectively. As results, the XRD patterns shows a pure perovskite single phase of BT was obtained by solid-state method at sintering temperature of 1000°C. While, the same result was obtained by co-precipitation at sintering temperature of 1100°C. The average crystallite size of BT-C and BT-S ceramics are in close values and getting larger with the higher sintering temperatures. Meanwhile, tetragonality of the BT-C tends to be larger as compared to the BT-S. The morphology results revealed big formed particles agglomeration (>5 μm) of the BT-C ceramics and the densities proportionally increased as the higher temperatures exhibited less porosity of ceramics. Meanwhile, the BT-S grains were visible and agglomerated in a much smaller size with the density values were different as the change of the sintering temperatures. The dielectric permittivity of the BT-C and BT-S ceramics were increased with higher sintering temperature. Further, the BT-C ceramics possessed higher permittivity than the BT-S due to high densities (less porosity) of ceramics. The highest permittivity of 1150 at 40 kHz was achieved by BT-C at 1200°C.

Structure refinement, defects evolution and calcium doping of Sr2CeO4 microwave dielectric ceramics with high quality factor

Sr2-2xCa2xCeO4 (x = 0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8) ceramics were synthesized through cold isostatic pressing and solid-state reaction. The microstructure, defects, microwave dielectric properties, and the effect of Ca2+ doping of Sr2CeO4 ceramics were systematically investigated. As the sintering temperature increased, the densities of Sr2CeO4 ceramics rose, the content of oxygen vacancies increased, and Ce4+ reduction would be enhanced. In addition, the Sr2CeO4 structure had poor compatibility with Ca2+. The major phase could be kept unchanged only when x ≤ 0.1. The reason was that the doping of Ca2+ intensified the distortion of the CeO6 octahedron and induced the structural transformation of the common edges (Sr2CeO4) to the common angles (SrCeO3). With the increase of dopant, the densities of Sr2-2xCa2xCeO4 ceramics increased significantly, while the content of oxygen vacancies also increased. The microwave dielectric properties were mainly influenced by the density, structural symmetry, defects, and the second phase SrCeO3. The dielectric permittivity (εr) of 13.4–15, the quality factor (Qf) of 118,580–52,170 GHz, and the temperature coefficient of resonant frequency (τf) of −58.3 ∼ −47.5 ppm/°C were obtained for Sr2-2xCa2xCeO4 ceramics When x ≤ 0.1. This work has provided a foundation for further research on cerate microwave dielectric ceramics.

Dense SiC ceramics prepared by using amorphous sintering additives

Spark plasma sintered SiC-based ceramics with amorphous Y2O3–Al2O3–SiO2 and CaO–Al2O3 sintering additives prepared by melt-quench approach, were compared with those with the direct addition of raw Y2O3–Al2O3–SiO2 and CaO–Al2O3 mixture. The relative densities of SiC-based with raw Y2O3–Al2O3–SiO2 and CaO–Al2O3 were 95.3% and 94.3%, respectively. In spite of the same composition of sintering additive, the relative densities of SiC-based ceramics reached the values of 98.9% and 99.5% by using the glassy additives of Y2O3–Al2O3–SiO2 and CaO–Al2O3, respectively, and the hardness of SiC-based ceramics was improved by about 22.2% and 17.2%, respectively. The amorphous sintering additive effectively improved the densification and hardness of SiC ceramics.

High-entropy (Ca0.5Ce0.5)(Nb0.25Ta0.25Mo0.25W0.25)O4 scheelite ceramics with high-temperature negative temperature coefficient (NTC) property for thermistor materials

(Ca0.5Ce0.5)(Nb0.25Ta0.25Mo0.25W0.25)O4 high-entropy ceramics with single scheelite phase structure were synthesized by solid-state reactions under a reducing atmosphere of argon, and their high-temperature electrical properties were investigated. The single scheelite phase of high-entropy ceramics is fabricated at a sintering temperature of 1300 °C, and grain sizes as well as relative densities of high-entropy ceramics increase with the increase of sintering temperature. High-entropy ceramics sintered at 1300 °C and 1400 °C exhibit excellent negative temperature coefficient (NTC) property within an ultrawide temperature range of 150 °C-1200 °C. Ceramic samples sintered under Ar tend to have lower activation energy, for the higher Ce3+ contents they possess than those sintered under air are in favor of increasing their polaron concentration. In comparison with conventional scheelite ceramics, high-entropy scheelite ceramics have a unitary NTC mechanism within a wider temperature range and a better aging property, for their crystal structure is stabilized by high-entropy effect at higher temperature.

Influence of CaO on microstructure and properties of MgAl2O4 transparent ceramics

Abstract Transparent magnesium aluminate spinel (MgAl2O4) ceramics were successfully fabricated from commercial spinel powders via air presintering and hot isostatic pressing (HIP) using CaO as sintering additive. The influence of the CaO content on microstructure, densification process and optical quality of MgAl2O4 ceramics were investigated. It was found that using CaO as sintering additive would prompt the sintering process significantly. The relative densities of MgAl2O4 ceramics presintered at 1525 °C change from 92.1% to 97.8% with the amount of CaO increasing from 0 to 0.15 wt%, and the average grain sizes of presintered MgAl2O4 ceramics increase from 0.4 μm to 0.8 μm, correspondingly. However, when the CaO content increases to 0.15 wt%, the secondary phase grains (calcium aluminate) occur in MgAl2O4 ceramics, which severely reduces the optical quality. The transparent MgAl2O4 ceramic with 0.125 wt% CaO presintered at 1525 °C for 3 h and HIP post-treated at 1600 °C for 3 h shows the best in-line transmittance of 86.3% at 1100 nm and 83.7% at 600 nm, the average grain size of 2.9 μm.

Sinterability and Dielectric Properties of LiTaO3-Based Ceramics with Addition of CoO.

Lithium tantalite (LiTaO3) is a common piezoelectric and ferroelectric crystal, but the LiTaO3 polycrystalline ceramics have rarely been reported, and their refractory character presents difficulties in their fabrication. In this study, LiTaO3-based ceramics with different amounts of CoO were prepared by pressureless sintering at 1250 °C, and the effects of the amount of sintering aid on the sinterability, microstructure, and dielectric properties of the ceramics were investigated. The relative densities of the LiTaO3-based ceramics were significantly improved by the addition of CoO powder. The LiTaO3-based ceramics achieved the highest relative density (89.4%) and obtained a well-grained microstructure when the added amount of CoO was 5 wt.%. Only the LiTaO3 phase in the ceramics was observed, indicating that the ions Co diffused into the LiTaO3 lattices and mainly existed in two forms: Co2+ and Co3+. The effects of the added amount of CoO on the dielectric properties of the LiTaO3-based ceramics were studied thoroughly. Consequently, the dielectric constant was enhanced, and the dielectric loss decreased in the LiTaO3-based ceramics with the addition of CoO. The optimal value was obtained at 5 wt.% of CoO-added LiTaO3-based ceramics.

Effect of CeO2 addition on the sintering behavior of the alumina‐rich calcium aluminate ceramics

AbstractIn this work, the CaAl4O7 ceramics and CaAl12O19 ceramics were fabricated by the solid‐state sintering technology and the effects of CeO2 as the additive on their sintering behavior subjected to sintering at temperatures of 1500°C, 1550°C, and 1600°C were investigated. It was demonstrated that the bulk densities of the CaAl4O7 ceramics and CaAl12O19 ceramics increased about 23.8% and 24.2% after adding 3.0 wt% of CeO2 than that of the samples without additives. Meanwhile, an increase in lattice parameters occurred in the CaAl4O7 ceramics and CaAl12O19 ceramics. The CeO2 could form the solid solution in the CaAl4O7 ceramics, inducing the lattice distortion and the activation of the lattice. The Ce4+ in CeO2 could be dissolved in the structure of CaAl12O19 phase and result in the structural defects, which would accelerate ion exchange and promote the in situ reaction of synthetic products. These behaviors could promote the sintering process of the CaAl4O7 ceramics and CaAl12O19 ceramics and improve their sinterability. Moreover, a considerable increase in bulk density occurred in both CaAl4O7 ceramics and CaAl12O19 ceramics with increasing sintering temperatures due to the greater densification obtained from the enhanced mass transport at elevated temperatures.

Effects of MnO2 addition on the microstructure and dielectric properties of LiTaO3 ceramics

Lithium tantalite (LiTaO3) is an excellent single crystal. At present, only a few research studies have focused on polycrystalline LiTaO3 ceramics because it is beset with difficulties for the fabrication of dense ceramic by conventional sintering. In this study, LiTaO3 composite ceramics with added different MnO2 contents were obtained by hot-pressing sintering at 1300 °C. The sinterability, microstructure, and dielectric properties of LiTaO3 composite ceramics were investigated. The relative densities of the LiTaO3 composite ceramics are remarkably improved by the addition of the MnO2 powder. The LiTaO3 ceramic achieves the highest relative density (98.6%) and exhibits a homogeneous microstructure following the addition of 3 wt% MnO2 sintered in N2. Only the LiTaO3 phase is observed at a MnO2 content addition below 3 wt%, and the secondary phase is found with further increases of added MnO2 (≥3 wt%) to the MnO2/LiTaO3 (MLT) composite ceramics. The dielectric properties of the MnO2/LiTaO3 composite ceramics are significantly influenced by the MnO2 contents, and the relatively optimal values are obtained when the addition of 3 wt% MnO2 sintered in N2.

Effect of oxygen content on the sintering behaviour and mechanical properties of SiC ceramics

In the current work, SiC powders with various levels of oxygen content were obtained by two ways: acid leaching and heat treatment; and these SiC powders were densified by a pressureless sintering technique with boron carbide and carbon additives. The techniques of X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscope, and mechanical testing were combined to examine the effects of oxygen impurities on the densification process of SiC ceramics. The experimental analyses indicated that high oxygen content is detrimental to the final sintering and mechanical properties of SiC ceramics. As the oxygen content increases from 0.55 to 2.10 wt%, the relative density and the hardness both decrease: the relative density drops from 98.53% to 70.55% (a 28% decrease), and the hardness drops from 27.1 ± 0.7 GPa to 6.7 ± 1.1 GPa (a 75% decrease). Furthermore, oxygen impurities can accelerate the abnormal growth and coarsening of SiC grains during sintering. In order to impede abnormal grain growth and achieve high densities of SiC ceramics, it is proposed that the oxygen content of the powders should be limited to less than 1.30 wt%.

Improvement of densification and microstructure of HfB2 ceramics by Ta/Ti substitution for Hf

AbstractUltrafine HfB2 powders were synthesized by the combination of borothermal reduction of HfO2 and solid solution of 5 mol% TiB2 or 5 mol% TaB2, prototypically, (Hf0.95Ti0.05)B2 and (Hf0.95Ta0.05)B2. The influence of substitution on the particle growth, high‐temperature stability, densification, microstructure, and mechanical properties of HfB2 was investigated. Results showed that the particle sizes of HfB2, (Hf0.95Ti0.05)B2 and (Hf0.95Ta0.05)B2 powders prepared by borothermal reduction at 1500°C were 1.73, 0.87, and 0.21 µm, respectively. The substitution of TaB2 led to a greater decrease in particles size than TiB2. After heat treatment at 1800°C, the particle sizes of HfB2, (Hf0.95Ti0.05)B2 and (Hf0.95Ta0.05)B2 powders increased to 2.60, 1.59, and 0.32 µm, respectively, indicative of the good high‐temperature stability of TaB2‐substituted HfB2. The relative densities of HfB2, (Hf0.95Ti0.05)B2 and (Hf0.95Ta0.05)B2 ceramics after spark plasma sintering at 2000°C were 76.1%, 85.2% and 99.8%, respectively. The fully dense (Hf0.95Ta0.05)B2 ceramics with fine microstructure showed comparably high Vickers hardness of 21.1 GPa combined with flexural strength of 521.2 MPa. It was proved that the solid solution of TaB2 could effectively inhibit the grain growth of HfB2 powders, and improve the densification, microstructure, and mechanical properties of HfB2 ceramics.

Influence of Al doping on structural, dielectric, and ferroelectric properties of multiferroic BiFeO3 ceramics

Lead-free BiFe1-xAlxO3 ceramics with x = 0, 0.005, 0.01, 0.015, and 0.02 were synthesised via the traditional solid-state reaction method. The effects of Al doping on the crystalline structure, dielectric, and ferroelectric properties were investigated. X-ray diffraction results indicated that Al doping increased the secondary phases (Bi2Fe4O9 and Bi25FeO39) when the Al content was above 0.015. Scanning electron microscopy images showed that the grain size in the BiFe1-xAlxO3 ceramics decreased from 1.6 to 0.45 µm with the increase of the Al content. Samples with a small amount of Al doping exhibited improvements in the remnant polarisation and dielectric constant compared with pure BiFeO3. However, when the Al content increased, the dielectric constant decreased and the polarisation hysteresis loops become unsaturated. With the increase of the Al content, the TC increased and exceeded 500 °C, and the leakage current densities of the BiFe1-xAlxO3 ceramics first increased and then decreased. These changes of the electric properties were related to the decrease of the grains size, the generation of secondary phases, and the increase of carriers.

Phase, Microstructure, and Microwave Dielectric Properties of (Mg0.95Co0.05)(Ti1−xSnx)O3 (0.05 ≤ x ≤ 0.20) Ceramics

Phase, microstructure, and microwave dielectric properties of (Mg0.95Co0.05)(Ti1−xSnx)O3 (0.05 ≤ x ≤ 0.20) ceramics prepared via the conventional solid-state route were investigated. X-ray diffraction analysis showed the existence of a single phase for the compositions with Sn4+ ≤ 0.15; however, a further increase in Sn4+ caused the formation of a secondary SnO2 phase in the ceramics. The maximum observed densities of the single phase ceramics were higher than 95% of the theoretical density. An increase in the lattice parameters of the ceramics were observed with an increasing Sn4+ content. Dense microstructures were observed for the single phase ceramics at a sintering temperature of 1400°C, whereas a porous microstructure was observed for the ceramics with secondary phase. The unloaded quality factor (Qufo) of the ceramics was found to increase initially with an enhancing Sn4+ content from 0.05 up to 0.15; however, a sudden downfall was detected with a further enhancement in Sn4+. The dielectric constant and temperature coefficient of resonant frequency of the ceramics were observed to decline monotonically with enhancing Sn4+ content.

Diffuse characteristics and piezoelectric properties of Tb-doped BCZT ceramics with CaCl2 as sintering aid

Lead-free ceramics 47(Ba0.7Ca0.3)TiO3–0.53Ba(Zr0.2Ti0.8)O3 (BCZT) + 0.2mol% Tb and xCaCl2 (x = 0.1,0.2 and 0.3wt%) were prepared at different temperatures (1300, 1350 and 1410℃) by solid-state reaction method. The experimental results reveal that dopants can effectively promote the growth of grain at relatively low sintering temperature and CaCl2 as the well sintering aid can produce a pronounced liquid phase to fill the gap between grains sintered at 1410℃ with 0.2wt%. Relative densities and piezoelectric properties of samples can be improved by the introduction of Tb and CaCl2. Comparing with pure BCZT, the residual polarization (Pr) and piezoelectric coefficient (d33*) of ceramics increase from 8.2 to 11.4μC/cm2 and 568–720pm/V with 0.2mol% Tb and 0.2wt% CaCl2 doped. The enhanced properties of samples may be related to the appearance of liquid phase which can increase relative densities of ceramics to 96% and the form of defect dipole in ceramics. Moreover, introduction of CaCl2 makes dielectric peaks (Tc) move to the high-temperature zone about 13℃ and become more and more diffuse (γ = 1.71–1.86), which may have the potential electro-caloric effect application in ferroelectrics.

Improved forming performance of β-TCP powders by doping silica for 3D ceramic printing

High-quality β-Ca3(PO4)2 (TCP) powders with the improved forming performance were prepared by doping silica in solid state method for 3D ceramic printing. The different concentrations of silica were employed as the sintering additive to investigate the effect on the dispersity of β-TCP powders, microstructures and the densities of as-prepared ceramics. The sintering additive could reduce the agglomeration of raw powders in the progress of ball-milling, and weakly agglomerated powders were obtained which meant improvement of formability. Meanwhile, the average grain sizes decreased and densities of as-prepared β-TCP ceramics increased with the increasing of silica doping concentration. The sample with the best performance was achieved with 1.0 wt% SiO2 when sintered at 1050 °C for 8 h in air. Its average grain size and relative density were 0.57 μm and 70.42%, respectively.