Solid State Double Sintering Method Research Articles

Nanomaterials and nanotechnology for composites: synthesis, structure, properties and new application opportunities

Nanomaterials and nanotechnology for composites: synthesis, structure, properties and new application opportunities

Dielectric properties of Na and Pr doped SrBi4Ti4O15 ceramics

Bismuth Layer-Structured Ferroelectrics materials (BLSFs) are widely used for many applications like resonators, filters, sensors, actuators and are appropriate for non-volatile Ferroelectric Random Access Memory (FeRAM) applications. The additional advantage of BLSF materials is that in electrical applications in they work at high temperatures. In the case of resonator applications, piezoelectric components are used as inductors. Usually BLSF materials typically have higher Curie temperature than PZT materials, so instead of PZT materials, BLSFs are used for high temperature piezoelectric sensor applications. SrBi4Ti4O15 (SBT) compound is a member of Aurivillius family Bismuth layered structured Ferroelectrics. The dielectric properties of Sodium and Praseodymium doped SBT, Sr0.2Na0.4Pr0.4Bi4Ti4O15 (SNPBT), prepared by solid state double sintering method using planetary ball mill, and is studied in the present work. Single phase is confirmed from XRD and microstructure is studied from SEM. The temperature dependence of dielectric constant and dielectric loss are studied at different frequencies. The Curie temperature increased by doping SBT with Na1+and Pr3+. Thus this piezoelectric ceramic is suitable for high temperature sensor applications.

Synthesis and characterization of multi functional NaNbO3-KNbO3 mixed ceramics

The Ferroelectric perovskite oxides in the form of single crystals, polycrystalline ceramics and thin or thick films constitute an important class of materials widely used in capacitors, electro mechanical systems, ferroelectric memories, etc. Ferroelectric ceramic materials NaxK1-x NbO3(NKN) are synthesized by solid state double sintering method. The synthesized materials are characterized using X-ray diffraction, SEM, EDS and DSC. Dielectric properties and impedance are studied.NKN is a highly researched material as a lead-free piezoelectric ceramic. It is a mixture between ferroelectric KNbO3 and anti-ferroelectric NaNbO3 where there is a morphotropic phase boundary (MPB) for the (Na0.52K0.48)NbO3 formulation; most research, however, is conducted at an equal ratio of sodium to potassium. Like BNT, NKN is known for its sintering difficulties, and suffers from deliquescence (degradation in contact with moisture). Typical properties of NKN include Pr and Ec of 15 µC/cm2 and 13 kV/cm. Doping NKN significantly improve the density, microstructure and piezoelectric properties. In the present study NKN samples with x= 0.0, 0.4, 0.5, 0.6 and 1 compositions are synthesized and characterized. The SEM micrographs indicate a gradual change in the morphology of the samples. For NaNbO3 samples spherical grains are observed. Growth of microfibers is observed in x= 0.5 samples. For higher compositions the microfiber morphology is changed to elongated grains. DSC of the samples showed phase transitions at around 320°C temperature. The x-ray diffraction studies indicate orthorhombic structure except x = 0.4. Dielectric constant versus temperature plots indicated ferroelectric to paraelectric phase transitions. These transitions are of diffuse type. Ferroelectric hysteresis loops are observed to be lossy type without saturation. Impedance spectroscopy studies show relaxation in the samples. The relaxations are observed in the temperature region of 400-600°C. The complex impedance plots in this temperature range indicate single semi-circle. The relaxations are observed to be of non-Debye type. The equivalent circuits contain parallel combinations of resistance and capacitance elements. The mechanism of relaxation is discussed in the paper. An attempt is made to understand the results obtained in terms of possible charge accumulation mechanism.

Effect of Sm and Na substitution on dielectric properties of SrBi4Ti4O15

The synthesis, characterisation, density and dielectric properties of Sm and Na substituted SrBi4Ti4O15 (SBT) piezoelectric ceramics are systematically studied for possible applications at high temperatures. The existing piezoceramics have temperature limitations. Samarium (Sm) and Sodium (Na) modified Strontium bismuth titanate Sr1-x SmxNaxBi4Ti4O15 (SSNBT-Strontium Samarium Sodium Bismuth Titanate) where x = 0.1, 0.2, 0.3 ceramics are prepared by solid state double sintering method using planetary ball mill for 10 hours duration in presence of Acetone media. Single phase is formed after calcination at 800 °C for 2 hours. Pellets are made with 1 cm diameter and 1 mm thickness using uniaxial Hydraulic press at 5 tonnes/cm2 pressure. All the samples are sintered at 1160 °C for 2 hours. The entire calcination and sintering processes are done in a programmable furnace. Orthorhombic structure of compound is confirmed by XRD analysis. The lattice parameters were calculated and experimental density was found to be around 95% of theoretical density. Tolerance factor decreased with increasing concentration of Sm, Na. The plate-like structure of grains is observed using SEM images and orientation of grains is random. Dielectric properties are reported as a function of temperature at different frequencies. The Curie temperature (Tc) of SBT is enhanced by substitution of Sm and Na in place of Strontium making this material a useful piezoceramic for high temperatures applications.

Synthesis and Characterization of Sodium Potassium Niobate and Cobalt Ferrite Multiferroic Composites

ABSTRACTThe composite materials with composition xNa0.5K0.5NbO3-(1–x)CoFe2O4 with x = 0.2, 0.4, 0.5, 0.6, 0.8, 0.9 and 1.0 are combination of ferroelectric Na0.5K0.5NbO3 (NKN) and ferrimagnetic CoFe2O4 (CFO) compounds. NKN is a combination of ferroelectric KNbO3 and antiferroelectric NaNbO3, with morphotropic phase boundary and exhibits two phase transitions around 220°C and 430°C. CFO is a ferrimagnetic material with inverse spinel cubic structure. Therefore the triphasic composite is expected to be a good magneto-electric material. NKN is synthesized by solid state double sintering method. XRD studies confirm single phase formation and orthorhombic structure. The composites are fabricated by taking stoichiometric amounts of NKN and CFO powders, ground for 6 h, made into green square pellets and kept for sintering at 1000°C for 5 h. XRD studies reveal the presence of peaks corresponding to both NKN and CFO. Density of the composites increased with addition of CFO; SEM images indicate the change in shape and size of grains. EDS studies confirm the presence of estimated atomic and weight percentages of all the composites. FTIR studies reveal the presence of multiple peaks in the 1000-1600 cm–1 region due to Na-O, K-O vibrations and at ∼450 and 584 cm–1 due to Fe-O and Co-O bonds. Dielectric measurements show the variation of transition temperatures with the change in composition. Impedance studies confirm the increasing conducting behaviour of composites with increasing concentration of CFO.

Effect of synthesis methods and a comparative study of structural and magnetic properties of zinc ferrite

Zinc ferrite samples were prepared by two different routes which are chemical co-precipitation and standard solid state double sintering method. Structural properties of ZnFe2O4 were determined, and initial particle size was found as 5 nm in the samples prepared by chemical co-precipitation technique. The XRD patterns showed the single phase of ZnFe2O4 spinel structure and confirmed by the lattice parameter and the unmixed hkl values for both the synthesis techniques. M-H curves at room temperature showed superparamagnetic nature of the samples sintered from 200°C to 600°C, synthesized by chemical co-precipitation technique. The Mössbauer analysis at room temperature showed a doublet which is the signature of superparamagnetic nature, and it is in agreement with the acquired M-H curves. The magnetization of ZnFe2O4 synthesized by chemical co-precipitation method was found higher than the magnetization of ZnFe2O4 synthesized by the solid-state double sintering method in the sintering temperature from 1100°C to 1300°C.

Microfiber growth and characterization of NaNbO3-KNbO3 ceramics

ABSTRACTFerroelectric ceramic materials NaxK1-x NbO3 (NKN), with x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0 are synthesized by solid state double sintering method. The synthesized materials are characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Differential scanning calorimetry (DSC) and Fourier Transform Infrared spectroscopy (FTIR). The x-ray diffraction studies indicate orthorhombic structure except for x = 0.4 (which has monoclinic structure). The SEM micro-graphs indicate a gradual change in the morphology of the samples. Growth of microfibers is observed in x = 0.5 samples. For higher compositions the microfiber morphology is changed.DSC of the samples showed phase transitions. Dielectric constant versus temperature plots indicated ferroelectric to paraelectric phase transitions. The complex impedance plots in higher temperature range are single semi-circles. The equivalent circuits contain parallel combinations of resistance and capacitance elements.

Study of dielectric and resonance and anti-resonance property of dielectric relaxor ceramic: [Ba(Nd0.1Ti0.8Nb0.1)O3]0.50[Na0.5Bi0.5TiO3]0.40[CaTiO3]0.10

ABSTRACT[BaNd0.1Ti0.8Nb0.1O3]0.50[Na0.5Bi0.5TiO3]0.40[CaTiO3]0.10 ceramic was prepared through solid state double sintering method. The XRD results indicate that the ceramic sample have a cubic structure at room temperature. The average grain size was found to be around 4–6 μm. Dielectric studies revealed that the present materials exhibit relaxor behaviour. From piezoelectric studies, it is observed that the resonance and anti-resonance peaks was broad for ceramic sample studied under clamped state when compared to ceramic sample studied under free State. The values of Kt & Keff at room temperature for ceramic samples studied under clamped state were 0.751, 0.718 respectively. Modified Lorentz equation was used to characterize the dielectric and resonance & anti-resonance behaviour and was found to best fit to the experimental data. The activation energy for thermally activated orientation of dipoles was in the range 80–90 μeV. The piezoelectric charge constant (d33) and piezoelectric voltage constant (g33) for the ceramic sample studied under free state are 1.359 × 10−9 (m/V) and 2.526 × 10−11 (m2/C) respectively.

Structural, Dielectric and Magnetoelectric Properties of x Co0.8Ni0.2 Fe2O4 + (1-x) PbZr0.55Ti0.45O3 Composites

In this paper, we are reporting structural, dielectric, ferroelectric and magnetic properties of polycrystalline composites (ferrite and ferroelectric) of PZT (PbZr0.55Ti0.45O3) + CNFO (Co0.8Ni0.2Fe2O4). The sample with composition x CNFO + (1-x) PZT (x = 0.00, 0.05, 0.10, 0.15 and 1.00) were prepared using the solid state double sintering method. Here the ratio x: (1-x) of two components is by weight. X-ray diffraction (XRD) studies show that lattice constant and tetragonality decreases with increasing ferrite content. Dielectric constant was found to decrease with increase in amount of CNFO. The value of tangent loss (tanδ) was reasonably low (< 0.04) for all the samples. Ferroelectric and ferrimagnetic behavior was confirmed by observing P-E and M-H hysteresis loop, respectively. The room temperature magnetoelectric coupling coefficient (α = dE/dH) was measured as a function of applied DC magnetic field. The value of α was observed to be maximum (855 μV/(cm.Oe)) at DC magnetic field of 1.7 kOe for sample with 5% CNFO. Value of piezoelectric coefficient ‘d33’ decreases from 133 to 60 pC/N.

Dielectric, Ferroelectric and Piezoelectric Properties of Sr0.8Na0.1Nd0.1Bi4Ti4O15 Prepared by Sol Gel and Solid State Technique

Effect of lower ionic radii (Na and Nd) substitution in A-site on the structure, dielectric, ferroelectric and piezoelectric properties of SrBi4Ti4O15 (SBT) is investigated in this paper. The samples are prepared by solid state double sintering method and sol gel method based on pechini process. Substitution of smaller ions reduced the dielectric constant and remanent polarization values. But sol gel samples showed good dielectric and ferroelectric properties. A-site substitution has resulted in improved Curie temperature and piezoelectric properties. As a result, Na and Nd modified SBT ceramics are found to be excellent high temperature piezoelectric materials.

Development of lead free magnetoelectric laminates of Na0.5Bi0.5TiO3–Tb0.3Dy0.7Fe1.95 for power generation

Lead free magnetoelectric laminates has been prepared by sandwiching Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) between two Tb0.3Dy0.7Fe1.95 (TDF) by epoxy bonding. The piezoelectric material Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) has been prepared by conventional solid state double sintering method and the magnetostrictive material, Tb0.3Dy0.7Fe1.95 (TDF) by vacuum induction melting process. NBT showed a saturated ferroelectric hysteresis behavior with the values of Ps=22.24μC/cm2, Ec=41kV/cm and Pr=27μC/cm2. The piezoelectric charge coefficient (d33) measured for NBT was 102pC/N. Magnetization versus magnetic field measurements were performed in longitudinal (L) and transverse (T) modes of TDF specimen that showed ferromagnetic hysteresis behavior. The magnetostriction of 950ppm at 4kOe and static strain coefficient of 0.37×10−6kOe−1 at 1kOe magnetic field were recorded for Tb0.3Dy0.7Fe1.95. The magnetoelectric output was measured in L and T modes for the different NBT thickness of 1.0, 1.5 and 2mm with TDF thickness of 1.5mm. The high magnetoelectric coefficient (α) was found to be 0.08mV/cmOe (L mode) and 0.13mV/cmOe (T mode) for the NBT/TDF laminates with 1.0mm thick NBT.

Interactive microwave and structural studies of C–Er2Si2O7

Abstract Er 2 Si 2 O 7 compound exists in three polymorphs, low temperature polymorph (type-B), monoclinic (type-C) and the high temperature monoclinic modification (type-D). The polymorphic Er 2 Si 2 O 7 is synthesized by solid state double sintering method. The crystal structure and surface morphology of the calcined samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The electromagnetic properties are measured through network analyzer (Agilent 8722ET). The dc electrical characterization is also performed in the microwave region and electrical transport data are analyzed according to Mott’s variable-range hopping. The activation energy (Δ E = 0.119 ± 0.001 eV) is calculated from lnρ versus 1 /k B T plot. Furthermore, the microwave electromagnetic properties of the samples were also studied at the frequency range from 20 Hz to 3 GHz on room temperature. It can be observed that C-type Er 2 Si 2 O 7 exhibit dielectric dispersion where both e′ and e′′ decrease slightly with increasing frequency up to 2.43 GHz, and then a resonance occurs around 2.85 GHz. This is the first kind of measurement on C–Er 2 Si 2 O 7 as far as our knowledge goes.

Powder synthesis and electrical, dielectric spectroscopic characterization of rare earth disilicates (D-Er2Si2O7): Transistor scaling-22 nm or beyond

Rare earth disilicates are now a day's being analyzed as a dielectric layer for transistor scaling for the advanced 22nm regime or beyond. So to explore these materials, the polymorphic powdered Er2Si2O7 (D phase) is synthesized by solid state double sintering method to study its characteristics. Structural characterization has been performed by X-ray diffraction. SEM and EDX results shows the rods like morphology of particles and composition. The dc electrical properties are evaluated by two probe method as a function of temperature. The dielectric spectroscopic measurements of D-Er2Si2O7 are performed in the temperature range 300–420K and frequency range 1kHz to 1MHz. The dc electrical transport phenomenon is analyzed using Mott’s variable-range hopping approach. The ac conductivity σac(ω) is obtained through the dielectric spectroscopic measurements.

Improved magnetoelectricity by uniaxial magnetic field pressed and sintered composites in BaTiO3 (x)–BaFe12O19 (1−x) system (x=0.8, 0.6)

A composite system BaTiO3 (x)–BaFe12O19 (1 − x) with ferroelectric BaTiO3 phase (BT) and a ferrimagnetic BaFe12O19 phase (BF), in which x varies from 0.8 to 0.6, have been prepared by solid state double sintering method. The presence of ferroelectric (BT) and ferrimagnetic phase (BF) have been confirmed from X-ray diffraction analysis, indicating the formation of composite system. Microstructure observation shows the distribution of BT and BF grains with respect to different compositions. With the variation of x in the composite system, a typical magnetic hysteresis loops have been observed at room temperature with high magnetization and coercivity values. The ferroelectric measurements have displayed hysteresis loops for x = 0.8 and 0.6 compositions. Magnetoelectric (ME) output have been recorded at room temperature for the both the compositions. The in situ magnetic field pressing at different magnetic fields followed by solid state sintering has enhanced the ME output value. Quadratic magnetoelectric signal is recorded indicating non-linearity in the system.

Samarium modified strontium bismuth niobate: Synthesis and ferroelectro-magnetic property evaluation

SrBi 2Nb 2O 9 (SBN) is an attractive ferroelectric material that is being considered in non-volatile random access memory cells. This study reports the effects of doping SBN at the Bi sites by the rare earth element Sm in the concentration range corresponding to x = 0–1 in the formula of SrBi 2− x Sm x Nb 2O 9. A solid-state double sintering method is adopted to synthesize and sinter the compounds starting from raw materials. It is shown that the crystal structure of SBN is retained but with slight changes to the lattice parameter. The sintered density, electric polarization and magnetization are enhanced by Sm addition. This system could be considered ferroelectromagnetic in nature.

Magneto-Electric Effect in Piezoelectric 0–3 Composites of Barium Titanate and Lithium Ferrite

Magneto-electric effect in piezoelectric 0–3 composites of Lithium ferrite/Barium titanate is studied. Composites are synthesized using two techniques (1) the solid-state double sintering method and (2) the sol-gel method. Magneto-electric coefficient is found to depend on the physical, electrical and magnetic properties of the constituent phases. Magneto-electric coefficients are obtained in the case of composites prepared by sol-gel method. An effort is made to relate the observed magneto-electric output to the properties of the individual phases and their connectivity.

Magnetostriction in composites of LiFe 5O 8–BaTiO 3

Polycrystalline lithium ferrite, LiFe 5O 8 was prepared by adopting two preparation techniques, the solid-state double sintering method and the sol–gel method. This ferrite powder was thoroughly mixed with barium titanate, BaTiO 3 for preparation of di-phasic composites of lithium ferrite and barium titanate. X-ray diffraction study of these composites revealed the presence of both the phases. Magnetostriction of these composites was measured in varying magnetic fields. The value of magnetostriction for the composites prepared by the sol–gel method was found to be higher than the values obtained in case of composites prepared by the solid-state method. Magnetostriction was found to decrease with increasing content of barium titanate. The saturation field was found to increase with the introduction of barium titanate.

Studies on electrical properties of SrBi4Ti4−3x Fe4x O15

The system SrBi4Ti4−3x Fe4x O15 belonging to bismuth layer structured ferroelectric (BLSF) materials withx = 0, 0.1 and 0.2 has been prepared through solid-state double sintering method. Increase of iron content in SrBi4Ti4O15 resulted in densification of the samples. The normal puckering observed in the sample has been found to decrease and the lattice distortion increased. Dielectric measurements indicate the ferroelectric transition temperature of the samples to be 530°C, 560°C and 606°C. The increase of transition temperature with increasing iron content is correlated with lattice distortion. Conductivity measurements show two slopes and the activation energies have been found to increase with the iron content. Impedance spectroscopy measurements confirm insulating behaviour at lower temperatures. With increase in temperature the samples become conducting and show relaxational effects. The Cole-Cole plots at higher temperatures are found to be semicircles. The relaxation times decrease with the increase of iron content.

Effect of HIPing on conductivity and impedance measurements of DyBi5Fe2Ti3O18 ceramics

X-ray diffraction, a.c. impedance and conductivity (a.c. and d.c.) have been used to characterize DyBi5Fe2Ti3O18. Samples were prepared by solid state double sintering method. A few samples were also subjected to hot isostatic pressing (HIP) at 800°C for 2 h at 100 MPa pressure. The data on XRD, impedance and conductivity of two sets of samples are compared to understand study of effect of HIPing on the properties of DyBi5Fe2Ti3O18

Synthesis and Electrical Properties of SmBi5Fe2Ti3O18

SmBi 5 Fe 2 Ti 3 O 18, a five layered bismuth oxide compound is synthesized using a solid-state double sintering method. DC conductivity, impedance, and AC conductivity are studied in the temperature range 30–500°C and frequency range 1 kHz–1 MHz. Complex impedance plots are used to separate grain and grain boundary contributions to electrical impedance. Activation energy for DC conductivity was found to be around 1.0 eV. The results are analyzed to understand the conductivity mechanism.