•PLZT comparable with PMN–PT and their hot-pressed counterparts synthesized.•HEM applied for ceramic preparation at reduced sintering temperature.•Strain value (0.27%) comparable to previous reported ...values for PLZT 8/60/40.•The electric field induced (strain) hysteresis loss was also found to be very less.
Substitution of lanthanum at the A sites of perovskite lead zirconate titanate ceramics shows an improvement in the structural and electrical properties. (Pb0.92La0.08)(Zr0.60Ti0.40)O3 (PLZT 8/60/40) was prepared using high energy mechano-chemical milling. The effect of milling on the microstructure and electrical properties of PLZT 8/60/40 has been studied. X-ray diffraction shows the phase formation after milling itself. TEM was used to measure the particle size. The SEM image of the sintered pellet shows a dense microstructure and the average grain size was found to be <1.5μm. Electrical properties of the ceramics were characterized. Piezoelectric charge coefficient (d33) was found to be 561pC/N. Resonance studies were performed on poled ceramics and the electromechanical coupling factor was calculated by the resonance method. The PLZT 8/60/40 composition showed a well saturated and uniform P–E hysteresis loop with remanent polarization (Pr) of 33.29μC/cm2 and a coercive field (Ec) of 10.57kV/cm. Electric field induced strain (S–E loop) shows a value of ∼0.27% with minimum loss.
(Pb0.92La0.08)(Zr0.60Ti0.40)O3 referred to hereinafter as PLZT 8/60/40 ceramics, near the morphotropic phase boundary region, show the ultra-high piezoelectric properties. Several attempts have been ...made and the said properties were related with processing (The combinatorial approach of mechanical activation and cold isostatic pressing), density, microstructure and MPB, however, still more clarification is required. In this study, more detailed and elaborated structural analysis was done for PLZT 8/60/40 ceramics. Slow scan X-ray diffraction data were collected from room temperature to elevated temperature and analysed by Rietveld refinement method, which confirms the coexistence of two phases at MPB, instead of the previously reported single tetragonal phase. These two phases have the tetragonal (P4mm) and monoclinic (Cm) symmetries. This monoclinic phase was supposed to be responsible for the origin of ultra-high piezoelectric properties in PLZT 8/60/40 ceramics. The changes in both phases were also studied as a function of temperature.
•It is believed that for PLZT ceramics MPB separates the tetragonal and rhombohedral phases.•A new monoclinic phase (C1m1) is found at the MPB of PLZT ceramics.•This C1m1 phase helps the rotation of polarization vector along the easy axis.•This phase is believed to be the origin of ultra-high electrical properties in PLZT ceramics.•The changes of C1m1 phase was also studied as a function of temperature.
In this paper, the polycrystalline ceramics Ba(1-x) (La, Na)xTiO30≤x≤0.08 were synthesized by microwave assisted heating of the starting materials. Room temperature X-ray diffraction along with ...Rietveld refinement analysis confirmed the formation of single-phase polycrystalline compound with the tetragonal crystal structure. A dense microstructure with several grains having different size distribution throughout the sintered pellet has been observed. The incorporation of La3+ and Na+ ions in BaTiO3 enhanced the room temperature relative permittivity. The studies of the temperature dependence of dielectric permittivity indicate ferroelectric-paraelectric phase transition with a clear shift in the Curie temperature (Tc) of BaTiO3 towards lower temperature side on co-substitution. The co-substituted sample with x = 0.08 exhibited superior dielectric constant (ɛ' = 4226) with low dielectric loss (tanδ = 0.0113) which is highly essential for the fabrication of ceramic capacitors. Resonance and antiresonance characteristics of impedance and phase for poled Ba(1-x)(La,Na)xTiO3 samples have been investigated in the frequency range of 300 kHz-1 MHz. Based on IRE standards for piezoelectric ceramics the piezoelectric response has been discussed. The room temperature P-E loop is investigated at an applied electric field of 80 kV/cm at 33 Hz frequency using Precision Premier II.
•Ba1-x(La,Na)xTiO3 (0 ≤ x ≤ 0.08) ceramic was prepared by solid state reaction method.•The permittivity increases with increasing x.•The dielectric losses and Curie temperature decrease with increasing x.•They are class II multilayer ceramic capacitor dielectrics suitable for MLCC.
•Ba(1−x)LixNix/2TiO3 (0 ≤ x ≤ 0.08) ceramic was prepared by solid state reaction method.•Electron interactions are strongly affected by increasing x.•The co-substituted ceramics show ferroelectricity ...and ferromagnetism simultaneously.
The structural, magnetic and ferroelectric properties of nickel and lithium co-substituted barium titanate were investigated in this work. Ba(1−x)LixNix/2TiO3 (x = 0, 0.02, 0.04 and 0.08) ceramics were synthesized via solid-state reaction with the assistance of microwave heating of the starting materials. The tetragonal structure has been observed in all samples, and it is confirmed by the Rietveld refinement study. The morphological study has been carried out by FE-SEM. Electron spin resonance (ESR) has been used to study the electron interaction and to verify the magnetism behavior of present samples. No resonance signal was observed in pure BaTiO3 samples. However, the resonance signal has appeared in the co-substituted samples. The result shows that the electron interactions are strongly affected by Ni2+ and Li+ concentrations. M-H loop was traced using VSM at room temperature. The results confirm that the sample with x = 0 shows an anti-ferromagnetic response. However, a ferromagnetic hysteresis loop arises with co-substitution. The emergence of M-H loops confirms the appearance of magnetic properties in Ni2+ and Li+ co-substituted BaTiO3 ceramics. The origin of magnetic behavior could be due to the carrier-mediated exchange interactions. Room temperature P-E hysteresis loop has been investigated at an applied electric field of 35 kV/cm and 33 Hz frequency. Measurements of room temperature ferroelectric and magnetic hysteresis loops indicate that the Ni2+ and Li+ co-substituted BaTiO3 ceramics show ferroelectricity and ferromagnetism simultaneously.
Samarium substituted SBTi (SrBi3.25Sm0.75Ti4O15) thin films were deposited in the temperature range of 675–750 °C on amorphous substrates using radio frequency (RF) sputtering technique. Amorphous to ...preferred crystalline nature and single phase formation was identified by X-ray diffraction analysis. Atomic force microscopy was used to capture the surface morphology and calculate the grain size. Microwave dielectric properties of SrBi3.25Sm0.75Ti4O15 thin films were investigated at 10 & 20 GHz. The highest dielectric constant (∼118 @ 10 GHz, 104 @ 20 GHz) was obtained for films deposited at 725 °C with preferred orientation. Nanoindentation and scratch tests were performed using nanoindentation technique in order to evaluate the nanomechanical properties of the SrBi3.25Sm0.75Ti4O15 thin films. The best hardness ∼9.6 GPa and Young's modulus ∼120 GPa was observed for the films deposited at 750 °C. This study explored that the films with preferred orientation have potential applications in ferroelectric random access memories and actuators.
Since the discovery of an effective role for defects in improving the performance of ceramic materials in practical application, investigation of defects and their impact on the development of ...optical properties in condensed matter physics have received widespread attention. In this work we synthesized a lead free (Ba0·60Sr0.40)(1-x)(Bi,Li)xTiO3 (BST6:BLx%); (0%≤x ≤ 8%) ceramics using a conventional solid-state reaction method. X-ray diffraction patterns along with Rietveld refinement, Micro-Raman (MR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), UV–visible, Electron Spin Resonance (ESR) and photoluminescence (PL) measurements are utilized to characterize these ceramics. XRD, and Raman analysis have proven cubic phase symmetry with a contraction in bond length as the Bi and Li concentrations increased. XPS and ESR results confirm the presence of Ti3+ surface defects (TSD) and oxygen vacancies (VO) on the co-substituted samples sintered at high temperature. The optical results show a decrease in the bandgap energy from 3.14 eV to 2.76 eV and a wide-PL band emission on the green band, caused by recombination of the radiative free electrons and holes trapped around the surface oxygen vacancies. Defect levels created within the bandgap might act as recombination centres, and this can give the possibility of using BST6:BLx as a green light emission source in future practical applications.
•Successful preparation of (Ba0·60Sr0.40)(1-x)(Bi,Li)xTiO3 (BST6:BLx%); (0%≤x ≤ 8%) ceramic.•The T3+ Surface defects (TSD) and oxygen vacancies (VO) were formed in these samples.•Decreasing the bandgap energy from 3.14 eV to 2.76 eV.•Successful correlation between the bandgap tuning and (TSD) and (VO).•This work may give a possibility to use these sample as green light emission source in future practical applications.
•Microwave absorption of prepared M-type Ba0·5Sr0.5CoxYxFe12-2xO19 ferrite compositions have been explored from 8.2 to 12.4 GHz.•Composition x = 0.2 owes reflection loss of −28.72 dB at 11.64 GHz and ...1.5 mm.•Compositionx = 0.8revealed a bandwidth to thickness ratio of 3.6 at 10.55 GHz.•The absorption characteristics were governed by primarily magnetic and dielectric loss, a quarter wavelength, and input impedance mechanism.•The investigated results exhibit absorber applications of prepared ferrites.
This work investigated the microwave absorbing characteristics of Co-Y doped BaSr Hexaferrites prepared by the ceramic method. X-ray analysis confirmed M-phase at low doping level compositions x = 0.0, 0.2 and traces of spinel phase for x > 0.2, and micrographs depicted the increase in grain size with dopants. The electromagnetic parameters were measured by a vector network analyzer at 8.2–12.4 GHz frequency band. Doping reduced the geometrical thickness of composition and increased the bandwidth/microwave absorption. The obtained results depicted that x = 0.2 composition has reflection loss (RL) of −28.72 dB at 11.64 GHz and 1.5 mm thickness and −10 dB absorption bandwidth of 3.11 GHz at 1.6 mm. x = 0.8 revealed a bandwidth to thickness ratio of 3.6 at 10.55 GHz. The role of the secondary phase and morphology in absorption enhancement has been discussed. The obtained results have the potential of compositions for designing a lightweight and wide bandwidth electromagnetic noise suppressor/absorber.
1 mm thick flexible few-layered graphene (FLG)/poly vinyl alcohol (PVA) composite sheets containing 0.1 and 0.5 vol.% of FLG are prepared using an easy solution mixing process followed by a simple ...casting process. As-synthesized FLG is used as the filler. The morphology, structure and phase characteristics clearly showed the formation of a composite. A maximum electromagnetic interference (EMI) shielding effectiveness (SE) of ∼19.5 dB (in the X-band, 8.2-12.4 GHz) was obtained in the case of the composite with 0.5 vol.% of FLG. Absorption is found to be the dominant mechanism for EMI shielding. The high EMI SE is attributed to the network-like features formed by FLG in the PVA matrix. EMI SE and absorption are understood by analyzing the dielectric behaviour, ac-conductivity and transparency to visible light of the composite sheets.
An excellent electromagnetic interference shielding effectiveness of ∼19.5 dB was measured for a 1 mm thick flexible few-layered graphene (FLG)/PVA composite sheet owing to the formation of network-like features by FLG in the PVA matrix.
Carbon fiber (Cf) reinforced reaction bonded silicon nitride (RBSN) composites with various amounts of fiber (5, 10, 15 and 20 vol %) are fabricated at 1400 °C using the direct nitridation method. ...The effect of Cf on the phase formation, microstructure evolution, mechanical and dielectric properties has been investigated. The XRD analysis using Rietveld refinement shows the presence of alpha and beta silicon nitride with a trace amount of tungsten disilicide. Microstructural analyses show the uniform dispersion of Cf in the RBSN matrix and the different toughening mechanisms operated in the composites. Mercury intrusion porosimetry results show unimodal to the multimodal distribution of pores with the increase in the quantity of Cf. The porosity of the composites varies from 30 to 38% with the addition of Cf. The addition of Cf has enhanced the fracture toughness of the composites only with 5 vol % Cf and the maximum toughness achieved is 2.5 MPa m1/2. There is no interface reaction on the Cf, which indicates the stability of fibers in the nitrogen atmosphere at 1400 °C. The dielectric performance of the composites in the X-band frequency range (8.2–12.4 GHz) is found to increase with Cf content.
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•Short carbon fiber reinforced silicon nitride composites were fabricated by reaction bonding method.•The increase of carbon fiber content has increased the porosity of the composites.•Pore size was varied from monomodal to multimodal distribution with the addition of carbon fibers.•Carbon fiber addition has enhanced the mechanical and dielectric properties of the composites.
