Solid-state Mixed Oxide Method Research Articles

Structural and electrical characterization of Gd and Li modified Bismuth Sodium Strontium Titanate

Structural and electric characteristics of Gd, Li and Sr modified Bismuth Sodium Titanate i.e. (Bi0.5Na0.5)0.6(Gd0.5Li0.5)0.2Sr0.2TiO3 (BNGLST) composition is demonstrated. BNGLST was synthesized by the solid-state mixed oxide method using the stoichiometrically weighed constituent oxides and carbonates. The homogenously wet mixed powder was calcined at 1000 °C for 12h and compressed pellets were sintered at 1250 °C for 2h. X-ray diffraction was carried out to confirm the phase formation. Crystallographic information was extracted from the Rietveld refinement of the XRD data. Dielectric measurement was carried out from room temperature to 300 °C at 1 kHz − 1 MHz frequencies. The a.c. conductivity associated with oxygen ion conduction is discussed in detail as a function of temperature and frequency.

Structural and electrical characterization of iron and lithium co-doped barium strontium titanate composite

This communication reports the effect of Iron (Fe) and Lithium (Li) co-doping on the structural, dielectric and electrical properties of Ba0.8Sr0.2TiO3; i.e. (Fe0.5Li0.5)0.1Ba0.7Sr0.2TiO3 (FLBST). The FLBST composite was synthesized by the solid-state mixed oxide method at 1400 °C for 12h. The crystalline phase formation has been confirmed by the X-ray diffraction technique and analyzed through the Rietveld Analysis using X’Pert Highscore plus software. From the XRD analysis, lattice parameters and the average crystallite size was calculated. The electrical properties of sintered (at 1450 °C for 2h) pellets were carried out in the temperature range of 30 °C–350 °C using impedance spectroscopy. Based on the real and imaginary part of the dielectric constant, i) the dipolar contribution which is dominant in 30 °C–150 °C is characterized by Curie-Weiss law and ii) contribution from defects and oxygen vacancies seen beyond 150 °C is described by Arrhenius equation.

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

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

Structural and Electrocaloric Investigation of the Lead and Strontium Modified Bismuth Sodium Titanate Ceramics

The Structural and Electrocaloric characteristics of Pb and Sr Modified Bismuth Sodium Titanate, i.e. Bi0.25Na0.35Sr0.3Pb0.1TiO3 (BNSPT) is reported. BNSPT Ceramics was synthesised by the traditional solid-state mixed oxide method. Stoichiometry-weighted constituent oxide and carbonates are mixed for 2 h in an acetone media and then calcined at 800 °C for 6 h. X-ray diffraction confirms the formation of a single-phase crystal structure. Further, lattice parameters were calculated using the Reitveld refined data and crystallite size was calculated by Debye-Scherrer’s equation. The dried powder was compacted in to pellets and sintered at 1250 °C for 2 h. The temperature dependence of maximum polarization was obtained from the P-E loop at a different temperature range from room temperature to 200 °C. The Electrocaloric properties of the BNSPT were measured by 500 V/cm using the Standard Thermodynamics Maxwell relation.

Effects of Ca3Co4O9 addition on physical and electrical properties of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3 ceramic

In the present work, highly dense complex perovskite oxide ceramics with the formula of (1-x)[Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3]-x(Ca3Co4O9) or (1-x)[BNKT-0.005LN]-xCCO, where x = 0, 0.010, 0.015, 0.020 and 0.025 mol fraction were fabricated by a solid-state mixed oxide method. After sintering at 1125 °C for 2 h, all ceramics were characterized in terms of physical, phase evolution, microstructure, dielectric, ferroelectric, and piezoelectric properties. XRD patterns of all samples indicated single phase of perovskite structure with good relative density value of ∼ 97 − 98%. The SEM image indicated that cubic-like shaped grains were observed in all samples. The average grain size was found to increase with increasing the modifier content. Optimum electrical properties (i.e. εr = 1485, tanδ = 0.0460, Pr = 13.13 µC/cm2, Ec =14.92 kV/cm and d33 = 145 pC/N) were found in the sample with x = 0.010 mol fraction.

Dielectric and optical spectroscopy of new polycrystalline ceramic for device applications

The polycrystalline double perovskite Li2GdFeTiO6 was synthesized through the solid-state mixed oxide method and its preliminary crystal structure was investigated by the XRD technique. The structure of the material was identified to be tetragonal with space group P4bm using POWD and MATCH software. The morphology of the sample was investigated through a scanning electron microscope (SEM) and the average grain size was found to be 3.82 μm using the intercept technique. The investigation of the perovskite phase and various vibrational modes were carried out through FTIR spectroscopic technique. The bandgap (Eg = 1.73 eV) and visible light sensitivity of the material were identified by UV–Visible spectroscopic operation carried in the range 200–700 nm. The dielectric and related properties were investigated as a function of frequency and temperature using an impedance analyzer (LCR meter). Room-temperature dielectric investigation suggests it may be useful for storage application. The transport activities investigated through conductivity, impedance, and modulus technique illustrate the significant influence of grains on transportation of charges.

Phase composition of ceramic samples of the BaTiO3–PbTiO3–BaZrO3 system near BaTiO3

Ceramics (1 − x) Ba(Ti1 – yZry)O3·xPbTiO3 with x = 0, y = 0; x = 0, y = 0.05; x = 0.05, y = 0.05; x = 0.10, y = 0.05; x = 0.15, y = 0.05; x = 0.20, y = 0.05 were obtained by solid-state mixed oxide method at 1400 °C. Phase composition of the ceramic samples was determined by the Rietveld method using powder diffraction data. At the first stage, the refinement was done for the two most representative sections of the registered XRD patterns, namely: 2θ = 44.6 °–46.2 ° and 2θ = 55.4 °–57.2 °. At the second stage, the refinement for the full XRD patterns was performed. The quantitative content of phases and their crystallographic data is determined. All samples contain a perovskite tetragonal phase (space group P4 mm). The cubic phase (space group Pm-3 m) is present in the samples with x = 0, y = 0; x = 0, y = 0.05; x = 0.05, y = 0.05; x = 0.10, y = 0.05. The orthorhombic phase (space group Amm2) is contained in the samples with x = 0, y = 0.05; x = 0.05, y = 0.05; x = 0.10, y = 0.05; x = 0.15, y = 0.05. Substitution of Ti for Zr in the tetragonal form of BaTiO3 reduces the tetragonal distortion of the unit cell. Substitution of Ba for Pb increases the tetragonal distortion of the unit cell.

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

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

Structure, infra-red, dielectric properties and conduction mechanism of Ti and Cu–Ti co-doped bismuth ferrite (BiFeO3): a comparison study

Multiferroic compositions BiFe0.90Ti0.10O3 and BiFe0.885Cu0.015Ti0.1O3 were synthesized by solid-state mixed oxide method. XRD studies confirmed rhombohedral crystal structure for both compositions while a little change in lattice parameters was observed with Cu–Ti co-doping. SEM analysis indicate that with co-doping comparatively smaller grains were evolved in the microstructure. Fourier-transform infrared spectroscopy (FTIR) was conducted to study absorption bands of different phases. High temperature A.C. conductivity (σac) analysis revealed the hopping charge conduction mechanism. Impedance spectroscopy (IS) was employed from room temperature to 230 °C in 100 Hz–1 MHz frequency range to analyze dielectric properties. IS data indicated decline in impedance with increase in temperature and frequency which confirms negative temperature coefficient of resistance (NTCR) behavior. Owing to the resistance–temperature characteristics, these compositions are well suited for thermal sensor applications.

Effects of Sintering Temperatures on Structural, Electrical and Mechanical Properties of BNKT Piezoelectric Ceramics

This research investigated the effects of sintering temperatures on the structural, dielectric, ferroelectric, piezoelectric and mechanical properties of lead-free Bismuth Sodium Potassium Titanate (BNKT) piezoelectric ceramics. The BNKT ceramics were prepared by solid-state mixed oxide method and sintering at temperature ranging from 1100 to 1150°C for 2 h. All ceramics sample showed highly density and reach a maximum at sintering temperature 1125°C of 5.81 g/cm3. X-ray diffraction patterns exhibited pure perovskite structure with coexisting of rhombohedral-tetragonal phases for all compositions. The microstructure was characterized by Scanning Electron Microscope (SEM), from SEM image the ceramics showed cubic-like grain shape. The average grain size increased with increasing sintering temperature. The dielectric permittivity showed the optimum sintering at 1125°C with reach a maximum dielectric constant of 4,194. Furthermore, at sintering temperature 1125°C present highest strain (Smax = 0.14%) with a large normalized strain coefficient (d*33 = Smax/Emax) of 233 pm/V.

An empirical model for B-site cation ordering in Ba(Mg1/3Ta2/3)O3

Processing-structure models are needed in both the lab and industry; however, few exist for cation ordering in perovskites. The perovskite Ba(Mg1/3Ta2/3)O3 in its ordered form is one of the best known high-Q dielectric materials but requires extended high-temperature annealing to achieve high degrees of order; so an empirical model which describes the ordering as a function of an easily obtainable processing parameter would be useful. In this work, powders of Ba(Mg1/3Ta2/3)O3 were synthesized using a conventional solid-state mixed-oxide method. The as-calcined compound had a cubic (lacking long-range B-site cation order) structure but contained short-range-ordered nanodomains. Upon annealing at 1500 °C for up to 40 h an increasingly ordered arrangement of Mg2+ and Ta5+ on the B site was generated, with the ordering causing a trigonal distortion. Empirical modeling as well as first-principles calculations via density functional theory showed that this ordering process was accompanied by a volume decrease despite the fact that ordered planes stack less efficiently. An empirical model was developed to describe the ordering parameter as a function of either annealing time or effective B-site contraction. The implication of this modeling method is that it may be possible to predict the degree of cation ordering in complex perovskite systems from ionic-radii data and experimentally-derived pseudocubic lattice constants alone. Conversely, it may also be possible to predict the degree of volume expansion/contraction upon ordering, which has implications for functional properties like ionic conduction.

Electrical transport in lead-free (Na0.5Bi0.5)1–xSrxTiO3 ceramics (x = 0, 0.01 and 0.02)

ABSTRACTLead-free (Na0.5Bi0.5)1xSrxTiO3 (x = 0, 0.01 and 0.02) ceramics were manufactured through a solid-state mixed oxide method and their ac (σac) and dc (σdc) electric conductivity were studied. It is shown that the low-frequency (100 Hz–1 MHz) ac conductivity obeys a power law σac ∼ ωs characteristic for disordered materials. Both the dc and ac conductivities have thermally activated character and possess linear parts with different activation energies. The calculated activation energies are attributed to different mechanism of conductivity. Frequency dependence of σdc and exponent s is reasonably interpreted by a correlated barrier hopping model. The NBT-ST system is expected to be a new promising candidate for lead-free electronic materials.

Effect of Li and Bi co-doping and sintering temperature on dielectric properties of PLZT 9/65/35 ceramics

In the present study, lead-lanthanum-zirconate-titanate (PLZT) ceramics were prepared by a solid-state mixed oxide method. Different amount of lithium carbonate and bismuth oxide (0.15mol%, 0.45mol% and 0.75mol%), where the ratio of Li:Bi =1:1 by mole, was added to PLZT to investigate the effect of Li and Bi co-doping. The ceramic samples were sintered at the temperatures of 1000, 1050, 1100, 1150 and 1200°C for 4h. After that, all samples were subjected to phase identification, physical property determination (sintered density and microstructure) and dielectric property measurement. It was found that doping of 0.15mol% Li and Bi resulted in maximum dielectric constant (εr =7819) when sintered at 1200°C. Grain size of PLZT ceramics was dependent on sintering temperature and dielectric properties were affected by the chemical composition rather than the grain size of the ceramics. Therefore, co-doping of Li and Bi was useful as it could improve the dielectric properties of PLZT ceramics.

Electrical Properties of Modified BNT Based Lead-Free Ceramics

The properties of modified Bi0.5Na0.5TiO3 (BNT) based lead-free ceramics were investigated. The BNT-based ceramics were prepared by a solid-state mixed oxide method Phase formation was determined by X-ray diffraction technique (XRD). The X-ray diffraction analysis of the ceramics suggested that all samples exhibited a perovskite structure without second phase. The value of dielectric constant increased with increasing in sintering temperature. Moreover, high sintering temperatures could improve ferroelectric properties of BNT base lead-free ceramics.

Influence of Al2O3 Nanoparticles' Incorporation on the Structure and Electrical Properties of Pb0.88Sr0.12Zr0.54Ti0.44Sb0.02O3 Ceramics

In this research, the effects of an Al2O3 nanoparticle additive on the structure and electrical properties of Pb0.88Sr0.12Zr0.54Ti0.44Sb0.02O3 (PSZST) ceramics were investigated. The PSZST ceramics with the addition of 0 – 2.0 vol % Al2O3 were fabricated via a solid-state mixed oxide method and sintering at 1250°C for 2 h to obtain dense ceramics. X-ray diffraction indicated that all compositions exhibited a single perovskite structure. Phase identification showed coexisting mixed rhombohedral and tetragonal phases for the modified ceramics, while the unmodified ceramics showed a rhombohedral-rich phase. The addition of Al2O3 nanoparticles was also found to improve the densification and the electrical properties of the PSZST ceramics, such as dielectric constant and polarization. The 2.0 vol% sample showed the highest low-field piezoelectric coefficient (d33) value of 646 pC/N, which was 90% higher than that of the unmodified sample, suggesting that this composition had the potential to be one of the prom...

X-ray Photoelectron Spectroscopy Analysis and Electrical Properties of Bi0.5(Na0.80K0.20)0.5TiO3-LiNbO3 Lead-Free Piezoelectrics

Lead-free piezoelectric ceramics with formula of (1-x)Bi0.5(Na0.80K0.20)0.5TiO3-xLiNbO3 or (1-x)BNKT-xLN (when x = 0, 0.005, 0.010, 0.015 and 0.020 mol fraction) were produced by a solid-state mixed oxide method. The ceramics with density ranging 5.38 - 5.68 g/cm3 were obtained by sintering at 1100°C. X-ray diffraction pattern showed that (1-x)BNKT-xLN ceramics exhibited pure perovskite structure. X-ray photoelectron spectroscopy analysis was used to identify of chemical composition, chemical state and binding energy of ionic species in the ceramics. Dielectric, ferroelectric and piezoelectric properties of all ceramics were investigated and found to be optimized at the composition of x = 0.005.

Effect of Bi3.99Ti2.97Nb0.03O12 Addition on Dielectric and Ferroelectric Properties of PZT Ceramics

In this study, bismuth niobium titanate Bi3.99Ti2.97Nb0.03O12; BNbT which is known as a bi-layer structured ferroelectric material was added into lead zirconate titanate (Pb(Zr0.52Ti0.48)O3; PZT). The ceramic with formula (1-x)PZT-xBNbT (x = 0.03, 0.05, 0,07, 0.15 and 0.20) were prepared by a solid state mixed oxide method. Phase analysis using XRD indicated that the pattern of the ceramic showed the single phase tetragonal of PZT, however, a BNbT peak appeared as BNbT content (x = 0.20) was increased. The microstructure of ceramic x = 0.03–0.15 had an equiaxed grain. With the addition of BNbT up to 0.20BNbT, the SEM micrographs also showed that plate-shaped grains started to dominate. The 0.97PZT–0.03BNbT ceramic showed the maximum dielectric constant (ϵr ∼ 679). With increasing amount of BNbT content, the dielectric constant and dielectric loss tangent gradually decreased. An addition, small amounts of BNbT content could improve normalized polarization (Pr ∼ 14.97 µC/cm2) of the ceramic.

Effect of Titanium Nitride on Properties of Hydroxyapatite-Based Composites for Biomedical Applications

Hydroxyapatite (HA) is widely used in biomedical applications as an artificial bone due to its excellent biocompatibility. In this work, the high purity HA powders were synthesized from natural bovine bone by a sequence of thermal processes. Then, the HA-based composites containing titanium nitride (TiN) at various compositions were fabricated by a solid-state reaction mixed oxide method. The green compacts were subsequently pressed and then sintered at 1200-1250°C for 2 hours. Surface morphology, compositions and phases of the as-prepared HA-based composites were analyzed by means of scanning electron microscopy (SEM) utilizing energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD), respectively. The results showed that the physical and mechanical properties and also the aesthetic performance of HA-TiN composites were substantially varied through the changes in the microstructure and volume fraction of the reinforcing particulates. The maximum hardness value of 3.5 GPa was obtained for HA-2wt%TiN ceramic sintered at 1250°C.

Effects of Dy Substitution for Bi on Phase, Microstructure and Dielectric Properties of Layer-structured Bi4-xDyxTi3O12 Ceramics

Bi4-xDyxTi3O12 (when x = 0, 0.25, 0.5, 0.75 and 1.0) powders and ceramics were prepared by solid-state mixed oxide method. The calcination was carried out at 900°C for 4 h with heating/cooling rate 5°C/min. The ceramics were then sintered at a temperature between 950–1100°C for 4 hrs. The optimum sintering temperature was found to be 1000°C. X-ray diffraction indicated the existence of orthorhombic phase for all sintering temperatures. Scanning electron micrographs of ceramic surfaces showed a plate-like structure with different grain size. The results of room temperature dielectric constant revealed that Dy dopant could dielectric constant of Bi4Ti3O12 ceramic where it was optimized at x = 0.25.

Phase-formation, microstructure, and piezoelectric/dielectric properties of BiYO3-doped Pb(Zr0.53Ti0.47)O3 for piezoelectric energy harvesting devices

Abstract This paper proposes a method for the composition and synthesis of lead zirconate titanate (PZT) piezoelectric ceramic for use in energy harvesting systems. The proposed material consists of (1− x )Pb(Zr 0.53 Ti 0.47 )O 3 – x BiYO 3 [PZT–BY( x )] ( x =0, 0.01, 0.02, 0.03, 0.04, and 0.05 mol) ceramics near the morphotropic phase boundary (MPB) region, prepared by a solid-state mixed-oxide method. The optimum sintering temperature was found to be 1160 °C, which produced high relative density for all specimens (96% of the theoretical density). Second phases were found to precipitate in the composition containing x ≥0.01 mol of BY. It is shown that the addition of BY inhibits grain growth, and exhibits a denser and finer microstructure than those in the un-doped state. Fracture surface observation revealed predominant intergranular fracture for x =0 and x =0.01, while a mixed mode of transgranular and intergranular fracture appeared for x ≥0.02. The optimal doping level was found to be x =0.01, for which a dielectric constant ( K 33 T ) of 750, a Curie temperature ( T C ) of 373 °C, a remnant polarization ( P r ) of 50 µC/cm 2 , a piezoelectric constant ( d 33 ) of 350 p C/N, and an electro-mechanical coupling factor ( k p ) of 65% were obtained. In addition, the piezoelectric voltage constant ( g 33 ), and transduction coefficient ( d 33 × g 33 ) of PZT–BY( x ) ceramics have been calculated. The ceramic PZT–BY(0.01) shows a considerably lower K 33 T value, but higher d 33 and k p . Therefore, the maximum transduction coefficient ( d 33 × g 33 ) of 18,549×10 −15 m 2 /N was obtained for PZT–BY(0.01). The large ( d 33 × g 33 ) indicates that the PZT–BY(0.01) ceramic is a good candidate material for energy harvesting devices.