Solid-state Mixed Oxide Method Research Articles

Effects of calcination temperature on phase formation and particle size of Zn2Nb34O87 powder synthesized by solid-state reaction

The solid-state mixed oxide method via a rapid vibro-milling technique was explored for the preparation of single-phase Zn2Nb34O87 nanopowders. Phase formation of zinc niobate was investigated as a function of calcination temperature by using a combination of thermogravimetric/differential thermal analyzer (TG/DTA) and X-ray diffraction (XRD) techniques. Morphology, particle size and chemical composition of the powders were determined by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) technique. The obtained results clearly revealed the influences of calcination temperature on phase formation and particle size of Zn2Nb34O87 nanopowder.

Improvement of Ferroelectric Properties of PZT Ceramics by SBT Addition

(1−x)PZT-xSBT ceramics were prepared by a solid-state mixed oxide method. Phase characteristics of (1−x)PZT-xSBT ceramics showed a PZT phase and new phase in the compositions with 0.1 ≤ x ≤ 0.3, while a mainly new phase was observed in the composition with x = 0.5. The tetragonality (c/a) of PZT phase decreased with increasing in SBT content up to x = 0.3. SEM micrographs of the sample surface showed equiaxed grains of the PZT phase and irregularly-shaped grains of the new phase in samples with 0.1 ≤ x ≤ 0.3. The 0.5PZT-0.5SBT sample showed mainly irregularly-shaped grains of the new phase. The ferroelectric properties of these samples showed that the addition of small amounts of SBT (x = 0.1) into PZT increased the remanent polarization.

Phase, microstructure and ferroelectric properties of new complex-structured ferroelectric ceramics in the PZT–SBN system

This study aimed to fabricate and characterize new complex-structured ceramics with formula (1-x)Pb(Zr0.52Ti0.48)O3–xSrBi2Nb2O9 or (1-x)PZT–xSBN (where x=0, 0.1, 0.3 and 0.5weight fraction). The ceramics were prepared by a solid-state mixed-oxide method and sintered at temperatures between 1000 and 1250°C. Optimum sintering temperature for this system was found to be 1050°C for 3h dwell time. X-ray diffraction patterns of (1-x)PZT–xSBN powders showed peak intensities of two-phase mixture corresponding to the relative amount of each phase as a result of SBN addition. Microstructure of (1-x)PZT–xSBN ceramics showed a variation in grain shape and grain size. The small addition of SBN (x=0.1) was also found to improve ferroelectric properties of pure PZT ceramic.

Properties of hydroxyapatite/zirconium oxide nanocomposites

Abstract Effects of zirconium oxide (ZrO 2 ) nanoparticles additive on the microstructure and physical properties of hydroxyapatite (HA) were investigated. The HA powder was derived from natural bovine bone by a sequence of thermal processes. The composites containing nanoparticles of ZrO 2 (0.2–1.0 vol%) were fabricated by a solid-state reaction mixed oxide method. All samples showed traces of HA, beta-tricalcium phosphate (β-TCP) and alpha-tricalcium phosphate (α-TCP) phases while the x ≥0.1 samples also showed ZrO 2 phase. Amount of β-TCP and α-TCP phases tend to decrease with ZrO 2 . The additive inhibited grain growth as a result of a decrease in grain size. However, the x =0.2 sample exhibited higher hardness value which is consistent with the density data. In addition, bioactivity test suggested that the additive promoted an apatite forming with the values of Ca/P close to the value obtained from HA.

Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic

Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba0.7Sr0.3)TiO3 [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, εr (1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

Phase formation and characterization of (1-x)PZT-xBNbT ceramics

This present study aims to fabricate and characterize a series of new complex-structured ceramics with formula (1-x)Pb(Zr0.52Ti0.48)O3−xBi3.99Ti2.97Nb0.03O12 or (1-x)PZT −xBNbT (when x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) using a solid-state mixed oxide method and sintered at temperatures in between 950-1050°C for 4 h with a heating/cooling rate of 5°Cmin−1. It was found that the optimum sintering temperature was 1000°C. The result of phase analysis using X-ray diffraction (XRD) indicated the existence of PZT-as well as BNbT-based solid solutions with corresponding lattice distortion. The solubility limit of ∼50 wt% PZT in BNbT was observed for BNbT-rich phase. Scanning electron micrographs of ceramic surfaces showed a plate-like structure in BNbT-rich phase which started to dominate at 0.5PZT–0.5BNbT composition. The microstructural evolution in this system was found to be in agreement with X-ray diffraction analysis.

Effect of lead zirconate titanate on microstructure, mechanical and electrical properties of bismuth sodium lanthanum titanate ceramics

Ferroelectric ceramics with formula (Bi0.487Na0.487La0.017)TiO3/xPb(Zr0.52Ti0.48)O3 (when x = 0, 0.1, 0.5, 1.0 and 3.0 wt%) were prepared by solid-state mixed-oxide method and sintered at 1050 - 1200°C for 2 h. The optimum sintering temperature was 1100°C at which all samples had the density at least 98% of theoretical values. X-ray diffraction results suggested that addition of PZT did not significantly affect unit cell of BNLT. An addition of PZT into BNLT effectively increased density and reduced grain size of the ceramics. These changes played an important role on mechanical properties improvement. Room temperature dielectric constant increased with increasing PZT concentration. The addition of PZT into BNLT slightly degraded ferroelectric properties, but improved the piezoelectric properties.

Effect of Li addition on phase formation behavior and electrical properties of (K 0.5Na 0.5)NbO 3 lead free ceramics

In this work, Li-modified KNN ceramic compositions ((K 0.5Na 0.5) 1− x Li x )NbO 3 with x = 0.03, 0.04, 0.05, 0.06, 0.65 and 0.07 were prepared by a conventional solid-state mixed-oxide method. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been found that a morphotropic phase boundary (MPB) between orthorhombic phase and tetragonal phases should exist between compositions with Li contents of 6–6.5%. The Curie temperature ( T c) of the ceramics shifted to higher temperature with increasing Li content. The room temperature dielectric constant was also seen to be higher than the pure KNN ceramics. In addition, the ferroelectric properties were found to enhance at near MPB compositions. This study clearly showed that the addition of Li could improve the dielectric and ferroelectric properties in (K 0.5Na 0.5)NbO 3 ceramics.

Effect of lanthanum substitution on microstructure and electrical properties of (Bi 0.5Na 0.5) 1−1.5 xLa xTi 0.41Zr 0.59O 3 ceramics

Bismuth sodium zirconate (BNZ) based ceramics with a composition of (Bi 0.5Na 0.5) 1−1.5 x La x Ti 0.41Zr 0.59O 3 where x = 0, 0.005, 0.01, 0.02 and 0.03 were prepared by a solid-state mixed oxide method and sintered at the temperature of 900 °C for 2 h. All the samples had relative density between 91 and 97% of their theoretical values. Phase analysis using X-ray diffraction indicated single rhombohedral or pseudo-cubic perovskite structure. SEM showed that addition of La caused the average grain size of the BNTZ ceramics to decrease as well as an improvement of sample density. Dielectric properties at room temperature measured at 10 kHz indicated that addition of La increased the dielectric constant. The results of ferroelectric characterization also revealed that adding La caused a decrease in coercive field without affecting the remanent polarization.

Ferroelectric properties of Pb(Zr 0.52Ti 0.48)O 3–Bi 3.25La 0.75Ti 3O 12 ceramics

The ceramic samples of compound (1 − x)Pb(Zr 0.52Ti 0.48)O 3– xBi 3.25La 0.75Ti 3O 12 (when x = 0, 0.03, 0.05, 0.07, 0.10, 0.15 and 0.20) were prepared by a solid-state mixed oxide method. X-ray diffraction analysis showed that complete solid solutions occurred for all compositions. Perovskite phase with tetragonal crystal structure and corresponding lattice distortion was observed. Scanning electron micrographs of sample surfaces showed equiaxed grains for all compositions. Ferroelectric measurements revealed that the addition of small amount of BLT ( x = 0.03) showed high remanent polarization (∼33.5 μC cm −2) and low coercive field (∼2.74 kV mm −1). Further increasing BLT content could maintain ferroelectric properties of PZT–BLT ceramics. Based on this study, ferroelectric properties of this PZT–BLT ceramic system can be improved for being further used in ferroelectric memory applications.

Structure–property relations of ferroelectric BaTiO 3 ceramics containing nano-sized Si 3N 4 particulates

Barium titanate/silicon nitride (BaTiO 3/ xSi 3N 4) powder (when x = 0, 0.1, 0.5, 1 and 3 wt%) were prepared by solid-state mixed-oxide method and sintered at 1400 °C for 2 h. X-ray diffraction result suggested that tetragonality ( c/ a) of the BaTiO 3/ xSi 3N 4 ceramics increased with increasing content of Si 3N 4. Density and grain size of BaTiO 3/ xSi 3N 4 ceramic were found to increase for small addition (i.e. 0.1 and 0.5 wt%) of Si 3N 4 mainly due to the presence of liquid phase during sintering. BaTiO 3 ceramics containing such amount of Si 3N 4 also showed improved dielectric and ferroelectric properties.

Effects BNT compound incorporated on structure and electrical properties of PZT ceramic

Ferroelectric ceramics with formula Pb(Zr 0.52Ti 0.48)O 3/ x(Bi 0.5Na 0.5)TiO 3 (when x = 0, 0.1, 0.5, 1.0 and 3.0 wt%) were prepared by a solid-state mixed-oxide method and sintered at the temperature between 1050 and 1200 °C for 2 h to obtain dense ceramics. It was found that the optimum sintering temperature was 1200 °C at which all the samples had relative density at least 96% of their theoretical values. Phase analysis using X-ray diffraction showed tetragonal and rhombohedral perovskite structure of PZT with no BNT peak detected, indicating that completed solid solutions occurred for all compositions. Scanning electron micrographs of fractured PZT/BNT ceramics showed equiaxed grain shape with mixed-mode of transgranular and intergranular fractures. Addition of BNT significantly decreased grain size of the PZT ceramic. Measurement of room temperature dielectric constant indicated a gradual increase with increasing BNT content. Results of ferroelectric characterization showed a slight decrease of remanent polarization and coercive field for BNT-added samples, suggesting ceramics which could be easily poled. Good piezoelectric coefficient ( d 33) could be maintained and comparable to that of pure PZT ceramic for the sample with 1.0 wt% BNT addition.

Preparation of CCTO Powders and Ceramics by a Simple Solid State Mixed Oxide Method

In this research, CaCu3.1Ti4O12.1: CC(3.1)TO ceramics were prepared by a simple solid state mixed oxide method. The optimum temperature for calcination the formation of phase pure perovskite and lattice parameters “a” of unit cell close to lattice parameter in the basis JCPDS file was found about 900°C for 8 h. Phase formation was examined by X-ray diffraction technique. The sintering process was carried out at 1000, 1025 and 1050°C for 8 h. The results show that the microstructure of fracture mode for variation sintered samples change from intergranular to intragranular mode with increasing sintering temperature. The density, average grain size, Vickers hardness and dielectric constant were increased with increasing the sintering temperature.

A role of BNLT compound addition on structure and properties of PZT ceramics

In this research, effects of lead-free bismuth sodium lanthanum titanate (BNLT) addition on structure and properties of lead zirconate titanate (PZT) ceramics were investigated. PZT ceramics with addition of 0.1–3.0 wt%BNLT were fabricated by a solid-state mixed oxide method and sintering at 1050–1200 °C for 2 h to obtain dense ceramics with at least 96% of theoretical density. X-ray diffraction indicated that complete solid solution occurred for all compositions. Phase identification showed both tetragonal and rhombohedral perovskite structure of PZT with no BNLT phase detected. Scanning electron micrographs of fractured PZT/BNLT ceramics showed equiaxed grain shape with both transgranular and intergranular fracture modes. Addition of BNLT was also found to reduce densification and effectively limited grain growth of PZT ceramic. Optimum Hv and K IC values were found to be 4.85 GPa and 1.56 MPa.m 1/2 for PZT/0.5 wt%BNLT sample. Among PZT/BNLT samples, room temperature dielectric constant seemed to be improved with increasing BNLT content. The maximum piezoelectric coefficient values were observed in pure PZT ceramic and were slightly decreased in BNLT-added samples. Small reduction of remanent polarization and coercive field in hysteresis loops was observed in BNLT-added samples, indicating a slightly suppressed ferroelectric interaction in this material system.

Effect of Si3N4 nanoparticulates on the mechanical and electrical properties of PZT ceramics

PZT/xSi3N4 ceramics (when x=0, 0.1, 0.5 and 1 wt.%) were prepared by a solid-state mixed-oxide method and sintered at 1125 °C for 2 h. X-ray diffraction results suggested that the addition of Si3N4 nanoparticulates did not significantly affect the unit cell and tetragonality of PZT. The addition of 0.1 wt.% Si3N4 effectively increased the density and reduced the grain size of PZT ceramics. These changes played an important role in hardness and fracture toughness improvement. The maximum room temperature dielectric constant was achieved in a PZT/0.1 wt.% Si3N4 sample. Within the Si3N4-containing samples, the high-temperature dielectric values and ferroelectric properties seemed to increase with increasing concentrations of Si3N4.

Fabrication–structure–properties relations of nano-sized NiO incorporated PZT ceramics

Ferroelectric PZT/NiO ceramics were fabricated using a solid-state mixed-oxide method. Effects of sintering temperature and content of nano-sized NiO addition (i.e. 0, 0.1, 0.5 and 1 wt%) on structure and densification of the ceramics were investigated. The tetragonality in tetragonal unit cell of pure PZT was found to decrease with increasing NiO content for sintering temperatures in between 1100 and 1200 °C. At a higher temperature of 1250 °C, high degree of tetragonality was maintained regardless of added NiO concentration. Density tended to increase with increasing amount of NiO. The grain size of PZT ceramics was also significantly reduced even with only 0.1 wt% NiO addition. The densest samples sintered at 1250 °C were chosen for mechanical and electrical measurements. Addition of NiO was found to improve hardness and only slightly affect fracture toughness. The maximum room temperature dielectric constant was achieved in PZT/0.1 wt% NiO sample which seemed to be the optimized composition in this study.

Effects of SiC nanofibers addition on microstructure and dielectric properties of lead titanate ceramics

Dense perovskite ferroelectric PbTiO 3 (or PT) ceramics reinforced with SiC nanofibers have been successfully fabricated by a simple solid-state mixed oxide and conventional sintering method. Phase formation, densification, microstructure and dielectric properties of the composites were investigated as a function of SiC content. Addition of SiC nanofibers to a PT matrix did not result in unexpected reaction phase. Microstructural observations revealed that some SiC nanofibers were heterogeneously dispersed in PT matrix and at the matrix boundaries. The grain size was decreased significantly with addition of SiC nanofiber. Though the densification and mechanical strength were improved, the dielectric properties of PT/SiC composites were degraded dramatically.

Microstructures of Zirconium Titanate Powders and Ceramics Prepared by Solid-State Mixed Oxide Method

Zirconium titanate (ZrTiO4): ZT powders were prepared by solid-state mixed oxide method. The mixed powder was calcined at various temperatures for 3 h ranging from 1100 to 1400 oC with a heating rate of 5 oC/min. X-ray diffraction analysis of the powders was performed using a diffractometer with Cu Ka. Pyrochlore phase was observed for calcinations below 1300 oC. In general, the strongest reflections apparent in patterns could be matched with a JCPDS file number 74-1504. The optimum calcination temperature for the formation of ZrTiO4 phase was found to be about 1300 oC for 3 h with heating rate of 5 oC/min. The microstructures of calcined powders were examined using scanning electron microscope (SEM). The particle size of powder increased with increasing calcination temperature. The ZT ceramics sintered at 1450, 1500, 1550 and 1600 oC for 4 h with heating rate of 5 oC/min, were checked for phase formation by X-ray diffraction. The density of sintered samples was measured by Archimedes method. The microstructures of sintered samples were examined using scanning electron microscope (SEM). The average grain sizes were checked by linear interception method. It was found that, the samples sintered at 1450 and 1500 oC gave rise to high purity ZT ceramics and the peaks matched well with ZrTiO4 phase in a JCPDS file number 74-1504. Unknown phases were found in ZT ceramics sintered at 1550 and 1600 oC. The value of density was in the range of 4.32 - 4.92 g/cm3 or 84.26 - 96.12 % of the ZT theoretical density. The densification of ZT ceramics decreased with increasing sintering temperature. The ZT ceramics sintered at 1450 and 1500 oC showed the average grain size of 8.55 and 12.55 µm, respectively. At sintering temperature 1550 and 1600 oC, morphology of grains changed to plate like crystals of second phases.

Structure–property relations of ferroelectric Pb(Zr0.52Ti0.48)O3–(Bi3.25La0.75)Ti3O12 ceramics

Ceramics with formula (1 − x )Pb(Zr 0.52 Ti 0.48 )O 3 – x (Bi 3.25 La 0.75 )Ti 3 O 12 (when x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) were prepared by a solid-state mixed-oxide method and sintered at 1150 °C for 4 h. All samples had densities at least 95% of theoretical values. Phase analysis using X-ray diffraction indicated the existence of BLT – as well as PZT – based solid solutions with corresponding lattice distortion. Scanning electron micrographs of ceramic surfaces showed a plate-like structure in BLT-rich phase while the typical grain structure was observed for PZT-rich phase. Ferroelectric measurements of these samples showed that addition of small amounts of BLT into PZT increased coercive field and remanent polarization to about 18 kV/cm and 12.5 μC/cm 2 , respectively. Further increasing the amount of BLT in PZT degraded the ferroelectric properties of the ceramics. This behavior was in agreement with their microstructures and dielectric properties.

Electrical and mechanical properties of ferroelectric lead zirconate titanate/tungsten oxide ceramics

Ferroelectric PZT/ xWO 3 ceramics (when x = 0, 0.5, 1, 3 and 5 vol%) were fabricated from PZT and nano-sized WO 3 powders by a solid-state mixed-oxide method. Phase characterization suggested that the reaction between PZT and WO 3 occurred during the sintering. This reaction seemed more pronounced with increasing the content of WO 3. The maximum density at approximately 97% of the theoretical value was achieved at 1 vol% of WO 3 addition. The grain size was reduced with an addition of WO 3 particles from ∼7.8 μm for PZT to ∼1.8 μm for 0.5 vol% WO 3 and ∼0.8 μm for 1–5 vol% WO 3. Mechanical properties of PZT could be improved with an addition of WO 3 nano-particulates. The addition of 0.5 vol% WO 3 could maintain good electrical properties while increasing WO 3 significantly reduced dielectric and piezoelectric constants of the PZT.