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The (1-x)Pb(Ni1/3Nb2/3)O3-xPb(Zr1/2Ti1/2)O3 (PNN-PZT) ceramic nanocomposites were fabricated via the bimodal particle sizes concept between nanosized PNN and micron-sized PZT powders. Crystal struc...

In this paper, the potential use of either amine-functionalized or hydroxyl-functionalized magnesium ferrite (MgFe2O4) nanoparticles (NPs) as Congo red nanoadsorbents is explored and compared. The ...

The hollow trimetallic Ag/Au/Pd nanoparticles with controllable Ag:Au:Pd ratio were successfully prepared by using a successive reduction method. Their optical properties, morphologies, structures, chemical compositions and electronic properties were carefully characterized by UV-vis, TEM, WDS, XRD and XPS techniques. The synthesized nanoparticles were also employed as catalysts for reduction of 4-nitrophenol. The results show that the trimetallic Ag/Au/Pd nanoparticles provided better catalytic activity than those obtained from bimetallic Ag/Au nanoparticles and monometallic counterparts. This study demonstrated that both atomic ratio of constituent metal and hollow interior structure strongly affect the catalytic activities of the synthesized Ag/Au/Pd nanocatalysts.

This work addresses the domain evolution processes in polycrystalline barium titanate (BaTiO3, BT)-based ceramics containing various amounts of gold nanoparticles (AuNPs) as an additive by using pi...

In this study, various sizes and chemical compositions of Au/Pd nanoparticles with core/shell structure were successfully prepared by employing a simple successive reduction method without addition of any stabilizer. The optical properties, morphologies, chemical compositions and crystal structures of the synthesized particles were fully characterized by using a combination of UV–vis spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, wavelength-dispersive X-ray spectroscopy, selected area electron diffraction and X-ray diffraction techniques. The catalytic activities of the synthesized Au/Pd nanoparticles for 4-nitrophenol reduction were also investigated and compared with monoatomic Au and Pd nanoparticles. The highest catalytic activity of bimetallic was obtained from AuPd 4 nanoparticles. With comparable size, Au/Pd nanoparticles provide better catalytic activity than those of monometallic Au and Pd. However, lower catalytic activities of Au/Pd nanoparticles are shown compared with that of smaller-size Au nanoparticles. This study also reveals that the size effect of catalysts plays important role on catalytic activity more than only changing their chemical constituents.

Lead zirconate titanate - lead zinc niobate (PZT-PZN) powders were prepared by a modified mixed-oxide synthetic route via a combination of Zn2Nb34O87 precursor and vibro-milling techniques. The effects of calcination temperature and chemical composition on phase formation were investigated by x-ray absorption spectroscopy. The Zn K-edge x-ray absorption near edge structure (XANES) was simulated with PZT-PZN in pyrochlore phase and perovskite phase. The comparison between simulated and measured XANES shows the increasing perovskite phase formation of PZT-PZN with increasing calcination temperature and the optimization of calcination temperature lead to 100% yield of PZT-PZN in perovskite phase. In addition, the Zn K-edge x-ray absorption near edge structure (XANES) was simulated with various compositions of PZT in PZT-PZN. The comparison between simulated and measured XANES shows the increasing perovskite phase formation of PZT-PZN with increasing composition of PZT. The results show the optimizati...

The potential utilization of two-stage sintering for the production of very dense and pure nickel diniobate (Ni4Nb2O9) ceramics with low firing temperature was demonstrated. The effects of the designed sintering conditions on the phase formation, densification and microstructure of the ceramics were characterized by using X-ray diffraction (XRD), Archimedes method and scanning electron microscopy (SEM), respectively. The minor phase of columbite NiNb2O6 tended to form together with the desired Ni4Nb2O9 phase, depending on the sintering conditions. Optimization of the sintering conditions may lead to a single-phase Ni4Nb2O9 ceramics with an orthorhombic structure. The ceramics doubly sintered at 950/1250 ◦C for 4 h exhibited a maximum density of ~92%. Microstructures with denser angular grain-packing were generally found in the sintered Ni4Nb2O9 ceramics. However, the grains were irregular in shape when the samples were sintered at 1050/1250 ◦C. Two-stage sintering was also found to enhance the ferroelectric behavior of the Ni4Nb2O9 ceramic.

In this work, the core-magnesium ferrite (MgFe2O4) nanoparticles were prepared by hydrothermal technique. Completed gold (Au) shell coating on the surfaces of MgFe2O4 nanoparticles was obtained by varying core/shell ratios via a reduction method. Phase identification, morphological evolution, optical properties, magnetic properties and cytotoxicity to mammalian cells of these MgFe2O4 core coated with Au nanoparticles were examined by using a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, UV-visible spectroscopy (UV-vis), vibrating sample magnetometry and resazurin microplate assay techniques. In general, TEM images revealed different sizes of the core-shell nanoparticles generated from various core/shell ratios and confirmed the completed Au shell coating on MgFe2O4 core nanoparticles via suitable core/shell ratio with particle size less than 100 nm. The core-shell nanoparticle size and the quality of coating influence the optical properties of the products. The UV-vis spectra of complete coated MgFe2O4-Au core-shell nanoparticles exhibit the absorption bands in the near-Infrared (NIR) region indicating high potential for therapeutic applications. Based on the magnetic property measurement, it was found that the obtained MgFe2O4-Au core-shell nanoparticles still exhibit superparamagnetism with lower saturation magnetization value, compared with MgFe2O4 core. Both of MgFe2O4 and MgFe2O4-Au core-shell also showed in vitro non-cytotoxicity to mouse areola fibroblast (L-929) cell line.

This paper demonstrates the adsorption capability of silica-coated magnesium ferrite nanoparticles (MgFe2O4@SiO2 NPs) for the selective adsorption of methylene blue (MB). The MgFe2O4@SiO2 NPs were generated from MgFe2O4 NPs by coating with a thin silica shell. After fully characterizing the MgFe2O4@SiO2 NPs, selective adsorption studies were carefully investigated by using three types of representative dyes: cationic (MB, rhodamine B, and malachite green), anionic (methyl orange and Congo red), and neutral (neutral red) dyes. Efficient removal of MB by the MgFe2O4@SiO2 adsorbents was observed for both individual and mixed dye systems, demonstrating excellent selectivity for MB. To optimize the adsorption capacity for MB removal, several parameters (i.e., initial solution pH, initial dye concentration, and contact time) were carefully investigated. In all cases, the magnetoresponsive adsorbents were easily separated from the solution by using an external magnet. Regeneration of the MgFe2O4@SiO2 NPs for MB removal was also performed to investigate the stability and reusability of the adsorbent. The recycling tests revealed that the MB removal efficiencies remained high after ten adsorption-desorption cycles. On the whole, the MgFe2O4@SiO2 NPs were found to be efficient, selective, and reusable adsorbents for MB removal.

Multiferroic (1 − x)Pb(Fe0.5Ta0.5)O3–xPb(Zr0.53Ti0.47)O3 (or PFT–PZT) ceramics were synthesized by solid-state reaction method. The crystal structure and phase formation of the ceramics were examined by X-ray diffraction (XRD). The local structure surrounding Fe and Ti absorbing atoms was investigated by synchrotron X-ray Absorption Near-Edge Structure (XANES) measurement. Dielectric properties were studied as a function of frequency and temperature using a LCR meter. A vibrating sample magnetometer (VSM) was used to determine the magnetic hysteresis loops. XRD study indicated that the crystal structure of the sample changed from pure cubic to mixed cubic and tetragonal with increasing PZT content. XANES measurements showed that the local structure surrounding Fe and Ti ions was similar. Dielectric study showed that the samples underwent a typical relaxor ferroelectric behavior while the magnetic properties showed very interesting behavior with square saturated magnetic hysteresis loops.

An approach to synthesize perovskite ferroelectric 0.9Pb(Zr0.44Ti0.56)O3-0.1Pb(Zn0.33Nb0.67)O3 or 0.9PZT-0.1PZN powders with a modified mixed-oxide synthetic route via a combination of the perovskite PZT phase stabilizer and the novel intermediate phase of Zn2Nb34O87 B-site has been developed. Phase formation, morphology, particle size, chemical composition and oxidation state of the products were investigated as a function of calcination temperatures. It has been found that the pyrochlore phase of Pb3Nb4O13 tends to form together with the perovskite phase of PZT-PZN, depending on calcination temperatures. It is seen that optimization of calcination condition can lead to a 100% yield of PZT-PZN in a tetragonal perovskite phase. The tetragonality factor, degree of agglomeration, crystallite size and average particle size tend to increase with the calcination temperatures. In addition, the synchrotron X-ray absorption near edge structure (XANES) analysis showed the oxidation state of Zn2+ atoms for all cond...

Mesoporous amine-functionalized magnesium ferrite nanoparticles (MgFe2O4–NH2 NPs), with maximum magnetization of around 35 emu g−1, were successfully synthesized and simultaneously functionalized under a refluxing condition by using ethanolamine as a surface modifier. The grafting of amine groups onto the MgFe2O4 NPs was clearly confirmed by the Fourier transform infrared spectrum. Adopting the MgFe2O4–NH2 NPs as a magnetic nanoadsorbent for Pb2+ removal from simulated wastewater containing heavy metals is reported. Characterizations of the adsorption ability of MgFe2O4–NH2 nanoadsorbent as a function of aqueous solution pH, initial Pb2+ concentration and agitating time, as well as their adsorption kinetics and adsorption isotherms, were also performed. The adsorption of 25 mL of 10 mg L−1 Pb2+ initial concentration onto 25 mg of MgFe2O4–NH2 nanoadsorbent reached equilibrium within 10 min at pH 4 with 99% removal efficiency. Kinetics and isotherms of the adsorption were fitted with pseudo-second-order model and Langmuir model, respectively, indicating the strong chemisorption through coordinative bond formation between the amine groups and Pb2+ ions. This MgFe2O4–NH2 nanoadsorbent possesses a maximum capacity, calculated from Langmuir equation, of around 135.1 mg g−1, which is higher than those of typical amine-functionalized adsorbents. Also, the selectivity experiments show that the MgFe2O4–NH2 nanoadsorbent provides higher selectivity coefficient values for Pb2+ than Ca2+, Cd2+, Zn2+, Cu2+ and Ni2+.

In this work, the investigation of phase formation, crystal structure, microstructure, microchemical composition and magnetic properties of perovskite (1−x)PFN–xPZT (x=0.1–0.5) multiferroic ceramics derived from a combination of perovskite stabilizer PZT and a wolframite-type FeNbO4 B-site precursor was carried out by using a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analyzer and vibrating sample magnetometer (VSM) techniques. The addition of PZT phase and its concentration have been found to have pronounced effects on the perovskite phase formation, densification, grain growth and magnetic properties of the sintered ceramics. XRD spectra from these ceramics reveal transformation of the (pseudo) cubic into the tetragonal perovskite structure. When increasing PZT content, the degree of perovskite phase formation and the tetragonality value of the ceramics increase gradually accompanied with the variation of cell volume, the M–H hysteresis loops, however, become narrower accompanied by the decrease of maximum magnetization (Mmax), remanent polarization (Mr), and coercive field (HC).

In the present work, the processing conditions for obtaining monodispersed magnesium ferrite (MgFe2O4) nanoparticles with the desired morphology and relatively high saturation magnetization via hydrothermal technique were developed. For the first time, the effects of base type and reaction conditions (i.e. temperature and time) on phase formation, morphology and magnetic properties of the obtained products were determined by using a combination of XRD, TEM/EDX and VSM techniques. It is seen that the saturation magnetization of the particles can be increased by employing lower reaction temperature and/or shorter reaction time, while narrow size distribution of the particles can be maintained. In addition, it was found that pure phase of superparamagnetic MgFe2O4 nanoparticles with the smallest size of about 65 nm was obtained by using CH3COONa as a base at 180 °C for 14 h.

The formation of perovskite phase, microstructure and dielectric properties of nanogold-modified barium titanate (BaTiO3) ceramics was examined as a function of gold nanoparticle contents by employing a combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Archimedes principle and dielectric measurement techniques. These ceramics were fabricated from a simple mixed-oxide method. The amount of gold nanoparticles was found to be one of the key factors controlling densification, grain growth and dielectric response in BaTiO3 ceramics. It was found that under suitable amount of nanogold addition (4 mol%), highly dense perovskite BaTiO3 ceramics with homogeneous microstructures of refined grains (~0.5–3.1 μm) and excellence dielectric properties can be produced.

In this work, BaTiO 3 ceramics modified with 0.5 mol% Au nanoparticles were fabricated by using a combination of the solid-state reaction and pressureless-sintering techniques. By employing a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Archimedes principle and dielectric measurement techniques, it was found that no phases other than tetragonal BaTiO 3 were observed in all ceramics. In contrast to the tetragonality, the relative density, grain size and maximum dielectric constant at Curie temperature of the ceramics were found to increase with sintering temperature. In addition, it has been found that, under suitable sintering temperature, dense perovskite nanogold modified BaTiO 3 ceramics with fine-grained microstructure (∼1 μm) and better dielectric properties than those of gold-free ceramics can be produced.

Binary multiferroic composites (1− x )BiFeO 3 – x Pb(Mg 1/3 Nb 2/3 )O 3 (BF–PMN; x = 0.0–50 wt%) were fabricated through a traditional ceramic process. The effect of the PMN contents on the phase assemblage, microstructure, dielectric and magnetic properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), LCR meter and vibrating sample magnetometer (VSM), respectively. The results indicate that all composites show that perovskite structure and PMN phase is compatible with the BF phase. The microstructure displays the mix phases between BF, PMN, Bi-rich BF and Fe-rich BF phases. Dielectric anomalies of these composites are totally different from BiFeO 3 single phase. Moreover, the dielectric constant is found to increase as the content of PMN decreases. Magnetic transition temperatures are in the range of 270–440 °C. Interestingly, the M – H hysteresis loop measurements indicated that all composites exhibited weak ferromagnetism behavior at room temperature. The maximum remanent magnetization M r is observed for x = 30 wt% and then decreases when the PMN content is more than 40 wt%.

The Pt deposited on hollow Ag/Au nanoparticles (Ag/Au/Pt) was successfully prepared by a successive reduction method. In general, no absorption peak at UV–visible region similar to that of Pt nanoparticles was observed for these Ag/Au/Pt nanoparticles. Almost spherical nanoparticles with average size around 20 nm were revealed by TEM. The presence of constituent metal of Ag/Au/Pt was confirmed by EDS. The catalytic properties of Ag/Au/Pt for methanol oxidation were investigated by cyclic voltammetry. The peak current density of the Ag/Au/Pt nanoparticles is higher than that of Pt nanoparticles, indicating their better potential of an electrocatalytic activity for methanol oxidation.

The time dependence of dielectric charge was investigated of Ba(Ti0.99-xMn0.01Tax)O3 as a function of x = 0.0, 0.5, 0.1 and 1.5 mol% through the dependency of the dielectric permittivity on the frequency. A two part signal is considered as a behavior of aging in ferroelectrics: one is the low electric field and the other is the high electric field. Aging of dielectric has been calculated under the dielectric decay function which corresponds to observed de-polarization according to aging effect driven by charged defects with high activation energy. It was found that the aging behavior change significantly with donor dopant concentration.

Multiferroic composites containing bismuth ferrite (BF) and lead magnesium niobate–lead titanate (0.9PMN–0.1PT) phases were fabricated by solid-state reaction, with 10–50 wt% of 0.9PMN–0.1PT. The phase formation behavior and microstructural features were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Information on the oxidation state of Fe ions was determined by the synchrotron X-rays absorption near edge structure (XANES) technique. A vibrating sample magnetometer (VSM) was used to characterize the magnetic properties. The results indicated that all composites showed a perovskite structure and the PMN–PT phase was compatible with the BF phase. The microstructure displayed mixed BF, PMN and PT phases. In addition, the presence of secondary phases (Bi 2 Fe 4 O 9 and Fe 2 O 3 ) was observed by both XRD and XANES techniques. The presence of BF, Bi 2 Fe 4 O 9 and Fe 2 O 3 phases was also confirmed by the oxidation state and the local structure surrounding the Fe absorbing atom, as observed in the Fe K-edge XANES spectrum. Moreover, the composites exhibited typical magnetic hysteresis ( M – H ) loops at room temperature. The maximum saturation magnetization ( M S ) was observed for x =30 and 40 wt%.

In this work, the effects of various two-stage sintering schemes on phase formation, microstructural development and dielectric properties of Zn 3 Nb 2 O 8 ceramics were systematically determined via a combination of scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and dielectric measurement techniques. In comparison with the conventional sintered samples, it was found that single-phase Zn 3 Nb 2 O 8 ceramics with maximum density of ∼99% theoretical density, smaller average grain size (∼3 μm) and better dielectric properties can be achieved via a two-stage sintering technique.

Renewed interest in the perovskite ferroelectric barium titanate (BaTiO 3 ) has been driven by the introduction of large recoverable electrostrain in doped BaTiO 3 -based materials. Our previous work demonstrated that the potential for high-performance in Pb-free ferroelectrics based on BaTiO 3 was confirmed in Fe 3+ /Nb 5+ -doped BaTiO 3 systems. It is well documented that the electronic behavior of BaTiO 3 is intimately related to the chemical state of the constituents. However, information regarding the chemical states of the ions of the Fe 3+ /Nb 5+ -doped BaTiO 3 ceramics is currently unavailable. Consequently, this study describes the chemical state of sintered hybrid Fe 3+ /Nb 5+ -doped BaTiO 3 ceramics, compared with undoped BaTiO 3 ceramics derived from the same processing. Analysis by X-ray photoelectron spectroscopy (XPS) showed that the binding energy of Ti indicates the presence of more than one component of Ti within the doped BaTiO 3 ceramics, but only one component of Ti within the undoped BaTiO 3 ceramics. Unlike Ti, the XPS spectra indicates that more than one type of barium and oxygen species exist in both undoped and doped BaTiO 3 ceramics.

The solid-state mixed oxide method via a rapid vibro-milling technique was explored for the preparation of single-phase Zn 2 Nb 34 O 87 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 Zn 2 Nb 34 O 87 nanopowder.

In this work, perovskite relaxor ferroelectric lead zinc niobate–barium titanate (0.93PZN–0.07BT) ceramics were fabricated by using a combination of Zn 3 Nb 2 O 8 B -site precursor and reactive sintering process. The effects of sintering condition on phase formation, densification, microstructure and dielectric properties of the final products have been investigated using a combination of X-ray diffraction, Archimedes density measurement, scanning electron microscopy and dielectric measurement techniques. It is seen that pure perovskite phase of PZN-BT solid solutions can be achieved in all samples. Density and average grain size values of sintered samples increased with sintering temperatures and dwell time. With appropriate sintering at 1150 °C for 5 h, 0.93PZN–0.07BT ceramics exhibited a peak dielectric constant of 11,497 and dielectric loss of 0.05 at the Curie temperature of 99 °C measured at 1 kHz.

Nanosized zinc oxide/lead titanate (ZnO/PT) ceramic matrix nanocomposites have been studied. Under an appropriate sintering condition, ZnO/PT ceramic nanocomposites were successfully fabricated by a pressureless sintering technique. Thermal expansion and polatization behaviors were determined by using the dilatometer. This technique measures the temperature-dependent of the strain, and the magnitude of polarization can be deduced from the sets of the thermal expansion data. The calculated electric polarization values on the ZnO/PT nanocomposite ceramics show the simple approach to determine the temperature dependence of the polarization below and around the transition temperature. Various aspects on understanding the polarization behavior and other effects in the ferroelectric are discussed.

In this study, compositions in the 0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr1/2Ti1/2)O3 based systems will be developed based on the material engineering approach (processing vs. electrical properties). This work involves the fabrication of high purity PZN-PZT based in ceramic forms, and a study of La2O3 addition on phase formation, microstructures and electrical properties was investigated which are especially important from the viewpoint of the development of practical piezoelectric materials. The effect of La2O3 addition was characterized on microstructure and electrical properties of PZN-PZT. Amounts of 0.05–1 wt% La2O3 were doped on 0.2PZN-0.8PZT. All compositions of powders were uniaxially pressed in pellets and sintered at the temperature 1250°C with dwell time 2 h. Phase and microstructure development, dielectric and ferroelectric properties of ceramics were characterized by XRD, SEM, LCR meter and Modified Sawyer–Tower Circuit respectively. In addition, the values of permittivity maximum and the temperature o...

Lead lanthanum zirconate titanate ceramics (PLZT) are well known for their excellent dielectric, piezoelectric and ferroelectric properties and electro-optic characteristics. The solid solutions of compounds are expected to possess very interesting properties, making them promising candidates for electromechanical devices. This study describes processing and sintering conditions and electrical properties of the PLZT ceramics (9/65/35) that were successfully prepared from the respective starting materials by vibro-milling mixed-oxide method at various soaking time conditions for optimized properties. A composition and microstructure of the ceramics were investigated using X-ray diffraction and scanning electron microscopy. The dielectric properties of the densified samples were examined as a function of temperature and frequency to verify the relationships between soaking time conditions, phase formation, densification, microstructural development, dielectric, and ferroelectric characteristics.

Influences of a combination between the two-stage sintering and the reaction sintering techniques on phase formation, microstructure and dielectric properties of relaxor perovskite 0.93Pb(Zn1/3Nb2/3)O3–0.07BaTiO3 or 0.93PZN-0.07BT ceramics were determined via X-ray diffraction, scanning electron microscopy and dielectric measurement techniques, respectively. Under suitable two-stage reaction sintering schemes, it was found that dense and pure perovskite 0.93PZN-0.07BT ceramics with fine grain size can be successfully achieved with better dielectric properties than those of ceramics from single-stage reaction sintering.

The aging behavior of 3 mol% Nb2O5Pb(Zr0.52Ti0.48)O3with addition of 0.1–3 mol% Cr2O3prepared via the solid-state reaction technique have been investigated. The aging rate increased with increasing Cr concentration from 0.1 to 0.6 mol%. Further increase in Cr concentration, the aging rate decreased dramatically. From ferroelectric hysteresis loops measurements, the decrease of polarization existed in all of concentrations.

In this work, the effects of a two-stage sintering technique on phase formation, microstructure and dielectric properties of perovskite relaxor ferroelectric lead nickel niobate-lead zirconate titanate 0.2PNN-0.8PZT ceramics were investigated by using composition of X-ray diffraction (XRD), scanning electron microscopy (SEM) and dielectric measurements techniques. It was found that the density and grain size values were observed to increase with decreasing the first sintering temperature (T1 ) in two-stage sintering method. Under suitable sintering scheme (850/1150°C for 2 h), highly dense and pure-phase perovskite 0.2PNN-0.8PZT ceramics with maximum dielectric constant of about 22016 at 1 kHz were obtained.

The simple mixed-oxide method via a rapid vibro-milling technique is explored in the preparation of pure zinc niobate (Zn3Nb2O8) nanopowders. The formation of the phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM/TEM and EDX techniques. It has been found that the minor phase of ZnNb2O6 tends to form together with the Zn3Nb2O8 phase, depending on calcination conditions. More importantly, it is seen that optimization of calcination conditions can lead to a single-phase Zn3Nb2O8 in a monoclinic phase.

xPb(Zr1/2Ti1/2)O3-(1−x)Pb(Zn1/3Nb2/3)O3 or xPZT-(1−x)PZN (x = 0.85–0.95)powders were prepared by a modified mixed-oxide synthetic route via a combination of Zn2Nb34O87 precursor and rapid vibro-milling techniques. Effects of calcination temperature on phase formation, morphology, particle size and chemical composition of perovskite ferroelectric powders in the solid solution of PZT-PZN system were investigated. Perovskite phase transition from a tetragonal to a coexistence of tetragonal and rhombohedral phases occurred as composition and firing temperature change. The tetragonality factor and degree of spherical grain shape were observed to increase with increasing PZT content. Moreover, the degree of agglomeration and averaged particle size of the PZT-PZN powders were also found to increase at higher calcination temperatures.

The aging of dielectric properties of Cr-Doped Pb(Zr0.52Ti0.48)O3 were investigated. The composition of Pb(Zr0.52Ti0.48)O3 with 0.1, 0.2, 0.4, 0.6, 1.0 and 3.0 mol% of Cr2O3 addition were prepared by conventional mixed oxide technique. The aging has been measured at room temperature after quenching from high temperatures above the Curie temperature. The dielectric aging of all compositions revealed relaxor aging behavior. The aging rate of stable stage obeyed a logarithmic time dependence, while the aging rate decreased with increasing Cr2O3 at low concentration (0.1–0.6). Further increase in Cr2O3 concentration, the aging rate turned to increase.

In this work, comparative studies of three different mixed-oxide synthetic routes i.e. the conventional, the B-site precursor and the combination of B-site precursor and perovskite phase stabilizer on phase formation, microstructure and dielectric properties of ferroelectric lead zinc niobate-based ceramics were demonstrated via a combination of X-ray diffraction, scanning electron microscopy and dielectric measurement techniques. It was found that dense, pure perovskite ceramics with homogenous microstructure and better dielectric properties can be obtained via the B-site precursor technique.

In this study, phase formation and the magnetic properties of bismuth ferrite–lead titanate multiferroic composites were investigated. Multiferroic composites consisting of antiferromagnetic bismuth ferrite (BiFeO3 or BF) and ferroelectric lead titanate (PbTiO3 or PT) were synthesized by the solid-state sintering method. The presence of pure phase in these composites was confirmed by X-ray diffraction (XRD). The microstructure and magnetic properties were investigated by means of a scanning electron microscope (SEM) and vibrating sample magnetometer (VSM), respectively. Structural transformation from rhombohedral in pure BF to mixed-phase between rhombohedral and tetragonal when added with 50 wt% PT has been revealed from XRD analysis. The magnetic properties are generally seen to reduce with an increase in the content of the PT phase. Interestingly, the M–H hysteresis loop measurements indicated that the composites exhibited superparamagnetic behavior at room temperature for all compositions, a noticeable contradiction to the magnetic behavior earlier reported for the BF–PT solid–solution.

Thermal expansion properties have been measured for the ceramic lead zirconate titanate–lead zinc niobate [(1 − x)PZT–(x)PZN] in the temperature range of −100 to +450 °C. For all ceramics examined, the deviations from the straight line below Burns temperature were observed. The dynamic polarization fluctuations in their relaxor compositions are believed to play a role in this deviation. Burns temperature was determined and the local polarization (P d) was calculated from the thermal expansion data. Various aspects of understanding the polarization behavior and other effects in this ferroelectric system were examined and discussed.

In this work, Li-modified KNN ceramic compositions ((K 0.5 Na 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 0.5 Na 0.5 )NbO 3 ceramics.

Despite the many previous studies of the synthesis and characterization of several perovskite ferroelectric materials which have potential applications in electronic and medical diagnostic devices, the synthesis and phase formation of the whole series in the solid solution of (1 − x )Pb(Ni 1/3 Nb 2/3 )O 3 – x Pb(Zr 1/2 Ti 1/2 )O 3 (PNN–PZT) system has rarely been studied. In this work, the phase formation, morphology, particle size and chemical composition of perovskite powders in the (1 − x )PNN– x PZT system were investigated. Powders were prepared by a modified mixed-oxide synthesis route for various chemical compositions under different calcination temperatures. It is found that the perovskite phase undergoes a pseudo-cubic to tetragonal transition as composition changes. The degree of spherical shape and agglomeration were observed to increase with increasing PZT content.

Effects of compressive stress on the dielectric properties of complex perovskite PZBT-PMNT ceramic were investigated. The dielectric properties measured under stress-free condition showed a composite nature with two distinct temperatures of dielectric maximum associated with PZBT and PMNT end members. The dielectric properties under the compressive stress were observed at stress levels up to 230 MPa using a home-built compressometer. The results clearly showed that the compression load significantly reduced both the dielectric constant and the dielectric loss tangent in every measuring frequency. The change of the dielectric constant with stress was attributed to competing influences of the intrinsic contribution of non-polar matrix and the extrinsic contributions of re-polarization and growth of micro-polar regions, while the clamping of the domain walls contributed to the stress-dependent changes of the dielectric loss tangent. Finally, a large drop of the dielectric constant after a stress cycle was likely caused by the stress induced decrease in switchable part of spontaneous polarization.

In this work, the surface composition and chemistry of perovskite PNN ceramics obtained from a columbite precursor were investigated using X-ray photoelectron spectroscopy. The PNN ceramics were bombarded with argon ions, after which the chemical state and composition were determined. The results show that the sputtering technique caused substantial changes in the chemical states of Pb and Nb, but no detectable change in the chemical state of Ni. Notably, ion bombardment led to the removal of absorbed oxygen species. Furthermore, the chemical composition of the PNN ceramics was altered by the sputtering process, where decreases in the atomic percentages of Pb and oxygen were observed, while increases in the atomic percentages of Ni and Nb were observed.

Hybrid-doped ferroelectric ceramics have recently been of great interest. Their electrical properties; however, remained mysterious, particularly the aging behavior. Therefore, the dielectric aging characteristics of the A-site hybrid-doped Na 1+ /Sm 3+ BaTiO 3 perovskite ceramics were investigated in this study. With the concentration of acceptor dopant (Na 1+ ) fixed at 1 mol%, while that of the donor dopant (Sm 3+ ) varied from 0.0 to 1.5 mol%, the hybrid-doped BaTiO 3 ceramics were prepared successfully by a conventional mixed-oxide method via vibro-milling technique. The results showed that the dielectric properties of all de-aged samples decreased noticeably with time. In all the samples with 0.5, 1.0 and 1.5 mol% Sm 3+ obviously the aging of dielectric constant and dielectric loss did not follow the conventional logarithmic law. The stretched exponential decay was found to suitably represent the aging behavior of these A-site hybrid-doped BaTiO 3 ceramics. A possibly cause of such behavior lies in the nature of relaxor-like behavior of these ceramics induced from a disruption of dipole ordering from Na 1+ /Sm 3+ substitution.

Zinc niobate, Zn3Nb2O8, dielectric ceramics were fabricated by sintering Zn3Nb2O8 nanopowders derived from a rapid vibro-milling technique at various temperatures. Phase formation, densification, microstructure and dielectric properties of the ceramics were investigated as a function of sintering temperatures (1000-1200°C), using a combination of X-ray diffraction, Archimedes density measurement, scanning electron microscopy and dielectric measurement, respectively. It has been found that single-phase Zn3Nb2O8 ceramics with maximum density of ~98% theoretical density can be successfully produced with appropriate firing temperature, without any firing additives. Moreover, it is seen that the dielectric properties are found to enhance with increasing sintering temperature and grain size.

A novel approach to synthesis cubic pyrochlore lead zinc niobate-based Pb1.88Zn0.3Nb1.25O5.305 nanopowders with a modified mixed-oxide method has been developed. To ensure a pure phase pyrochlore formation, an intermediate phase of Zn3Nb2O8 was employed as key precursor. The formation of pyrochlore phase in the calcined lead zinc niobate powders has been examined as a function of firing temperature by a combination of TG-DTA and XRD techniques. The morphology evolution has been examined by SEM technique. It has been found that the unreacted PbO and Zn3Nb2O8 phases tend to form together with lead zinc niobate, with the latter appearing in cubic phase. It is seen that optimization of firing temperature can lead to a single-phase Pb1.88Zn0.3Nb1.25O5.305 powders with average particle sizes ranging from 75-400 nm.

In this paper, we report on the dielectric properties of PbTiO 3 /ZnO ceramic nanocomposites prepared by a conventional solid-state reaction method with improvement in densification by the addition of ZnO nanowhiskers. Phase formation, densification, microstructure and dielectric properties of the composites were investigated as a function of the content of ZnO nanowhiskers. Densification behavior of the ceramic nanocomposites was significantly enhanced, as compared to pure PbTiO 3 ceramics. Moreover, the dielectric constant of the composites was higher than that of the pure PbTiO 3 ceramics.

Perovskite relaxor ferroelectric PMN ceramics, Pb (Mg1/3Nb2/3O3), have been fabricated using a two-stage process employing a corundum-type Mg4Nb2O9 as a key precursor. The 100% perovskite PMN ceramics was revealed by X-ray diffraction analysis. The SEM image of the PMN ceramic shows irregular shape PMN grains on the porous surface. The surface chemical composition of the PMN ceramics could be characterized by X-ray photoelectron microscopy technique. The XPS results indicate most of the elements consist of more than one chemical species. The important of XPS studies here can reveal small amount of species which could not detected by XRD.