Search

Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 composites have been synthesized via sol-gel chemical route. We have systematically investigated the influence of sintering temperature on the structural and electrical properties of the BZT-BCT composites. The 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 composites were prepared by combining Ba(Zr0.2Ti0.8)O3 (BZT) and (Ba0.7Ca0.3)TiO3 (BCT) powders and sintered at different temperatures 900-14000C. The electrical properties of BZT-BCT composites improve with increasing sintering temperature. The composites sintered at 1300 and 14000C exhibit enhanced ferroelectric properties with spontaneous polarization Ps ~ 11.2 μC/cm2 and 8.66 μC/cm2 respectively. The dielectric and piezoelectric properties of BZT-BCT composites also improve with increasing sintering temperature. The dielectric constant value εʹ ~ 2938, tan δ ~ 0.016 and piezoelectric co-efficient d33 ~ 278 pC/N were measured for BZT-BCT composite sintered at 14000C while observing a considerably high transition temperature of Tc ~ 1200C. The observed results are discussed in terms of structural and microstructural analysis as a function of sintering temperature.

In this work, Pb-free Ba0.85Ca0.15Hf0.10Ti0.90O3 (BCHT) ferroelectric ceramic was synthesized via the sol-gel method and its structural, dielectric, ferroelectric, electrocaloric, and energy storage characteristics have been investigated under a low electric field of 20 kV/cm. The Rietveld refinement of XRD patterns shows good agreement with the co-existence of two phases tetragonal (P4mm) and cubic (Pm3m), with each phase contribution of 58 and 42% respectively. A volumetric porosity of around 11.5% is observed. The electrocaloric temperature change ΔT and entropy change ΔS have been estimated by an indirect approach using Maxwell relations. The room temperature value of – ΔS and ΔT are 0.207 J/Kg.K and 0.157 K respectively and a wide temperature span of 50K was observed. The room temperature observed enhanced total energy density, recoverable energy density, and energy storage efficiency were 84.43 mJ/cm3, 64.38 mJ/cm3, and 76.25 % respectively. The maximum energy storage efficiency of 85.03% was observed at 80oC. The Pb-free BCHT ceramic is a promising candidate for eco-friendly cooling and energy storage technology.

Lead-free Ba1−xCaxZr0.1Ti0.9O3 thin films were deposited by sol-gel synthesis route. Dielectric studies demonstrate that the BCZT film for x = 0.15 exhibits a high dielectric constant e′∼5838 and a...

In this work, lead-free (1-x) Ba0.85Ca0.15Zr0.1Ti0.9)O3–xCoFe2O3 (BCZT-CFO, x = 00, 0.2,0.8 and 1) multiferroic composites have been prepared by chemical solution technique and sintered at 1300 °C. The article is focused on a systematic study of phase dominance effect on structure, microstructure, dielectric, magneto-dielectric, magnetic, electric, and magneto-electric properties of the BCZT-CFO composites. The XRD study confirms perovskite phase in BCZT, cubic spinal phase in CFO and mixed structural evolution in composite samples without any traceable secondary phase formation. William-Hall equation has been used to evaluate strain kinetics in pure and composite samples. The scanning electron micrographs show dispersion of smaller BCZT grains in larger CFO grains matrix. The dense microstructure has been observed for composite sample with ferrite phase dominance. The room temperature dielectric study reveals frequency-dependent dielectric dispersion characteristics for composites and pure CFO. The enhanced dielectric properties are observed for composite sample with ferroelectric phase dominance. The room temperature magneto-dielectric behavior has been observed for lead-free multiferroic composites. Under magnetic study, observed typical ferromagnetic M-H hysteresis loop reveals presence of long-range ferromagnetic ordering in pure CFO as well as in composite samples. The highest value of Ms ~ 38.2 emu/g and Mr = 1.2 emu/g has been measured for ferrite phase dominant composite sample. Higher coercive field Hc value has been observed for composite with ferroelectric phase dominance. Leakage current characteristic has been investigated at and above room temperature for prepared samples. The composite with ferrite phase dominance has shown higher leakage current characteristics. The enhanced magento-electric coupling coefficient has been measured for composite with higher ferrite phase concentration.

Multiferroic composites consisting of Na0.5Bi0.5TiO3(NBT) and NiFe2O4(NFO) phases have been synthesized by using sol-gel and metal-organic decomposition (MOD) methods. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results confirm NBT and NFO phase formation in all composite samples without the presence of any intermediate phases. The phonon vibrational modes of the composite samples are detected by Raman spectroscopy over wavenumber regions from 100 to 1000 cm−1 at room temperature. The dielectric constant and dielectric losses are measured over a wide range of frequencies from 1 kHz to 1 MHz at room temperature. Room temperature magnetization measurements confirm the ferromagnetic behavior of all the composite samples. The observed values of coercivity are significantly lower and lie between 9.5 and 49 Oe only, which signifies the soft magnetic behavior of samples. The highest leakage current density value (3.39 × 10−6) has been observed for 50NBT-50NFO composite in I–V measurements. The present study reveals that NBT-NFO composites could be potential lead-free multiferroic composites and provide an alternative for designing environment-friendly devices.

This article describes preparation of Barium (Zirconium) Titnate (BaZr0.2Ti0.8O3) ceramics by the sol–gel technique and its structural, dielectric, ferroelectric, and piezoelectric properties investigated with sintering temperature variation. The phase and microstructure analysis of the sintered ceramics was carried out by X-ray diffraction method (XRD) and scanning electron microscopy (SEM), respectively. XRD analysis revealed structural transformation from cubic to tetragonal phase with increase in sintering temperature. Dielectric properties have been measured with variation of frequency up to 1 MHz and with temperature up to 200 °C. The BZT ceramics exhibit diffuse phase transition with normal ferroelectric behavior. Hysteresis loop measurements disclosed that BZT ceramics have good ferroelectric nature with saturation at higher applied electric fields. Leakage current density show negative temperature coefficient resistance (NTCR) behavior. The highest value (261 pC/N) of piezoelectric coefficient (d33) has been obtained for BZT ceramic sintered at 1400 °C and revealed that ceramics have great potentials for electronic industry based on sensor technology.

Na0.5Bi0.5TiO3 (NBT) and CoFe2O4 (CFO) ceramics were synthesized by sol–gel and metallo – organic chemical solution methods respectively. Structural, electrical, dielectric and magnetic properties of (1-x) NBT-(x) CFO (x = 0.1, 0.2) multiferroic particulate composite prepared by mixing NBT and CFO powders in required stoichiometric concentration were studied. The presence of ferroelectric (NBT) and ferrite (CFO) phases had been confirmed by X-ray diffraction analysis (XRD). Room temperature dielectric behavior was studied with varying frequencies. Ferromagnetic behavior was also confirmed by M−H hysteresis loops. The current–voltage (I–V) characteristics were studied by using Keithley 2611 Source Meter.

Na0.5Bi0.5TiO3 (NBT) and CoFe2O4 (CFO) powders have been prepared by sol-gel and metallo – organic (MOD) chemical solution methods respectively. The lead-free 50NBT-50CFO multiferroic particulate c...

Lead free Ba0.7Ca0.3O3 (BCT) ceramic has been synthesized by sol-gel method. Properties of ceramics are studied at sintering temperatures of 850 °C and 1050 °C. Structural Confirmation done...

The search for lead-free high performance magnetoelectric multiferroic materials at room temperature continues to be stimulated from the perspective of designing environmentally friendly multifunctional devices. In this context, lead-free composite thin films consisting of Ba1-xCaxZr0.10Ti0.90O3 (BCZT, x = 0, 0.10 and 0.15) as the ferroelectric/piezoelectric phase and Ni0.92(Cu0.05Co0.03)Fe2O4 (NCCFO) as the ferromagnetic/magnetostrictive component have been grown on Pt/TiO2/SiO2/Si substrates via chemical solution spin-coating method. The phase and structural evolutions of two distinct pure phases of as grown NCCFO/BCZT composite films were confirmed using X-ray diffractrometry (XRD) and field emission scanning electron microscopy (FE-SEM). The multiferroic, magneto-dielectric and magnetoelectric properties of the NCCFO/BCZT composite films have been investigated. Moreover, significant enhancement of multiferroic properties and magnetoelectric effect was observed in these composite films when compared to those reported recently for other lead-free BCZT based multiferroic composites. The magnetic studies demonstrate that the NCCFO/Ba0.90Ca0.10Zr0.10Ti0.90O3 (NCCFO/BCZT10) composite film exhibits a large saturation and remnant magnetization of Ms ∼ 346.2 emu/cm3 and Mr ∼ 73.5 emu/cm3 respectively having a coercive field of Hc ∼ 73.5 Oe. The NCCFO/BCZT10 composite film also exhibits good ferroelectric properties with saturation polarization Ps ∼26.7 μC/cm2, remnant polarization Pr ∼8.9 μC/cm2 and coercive field Ec ∼82.7 kV/cm. The observed magneto-dielectric effect is of two orders higher than those reported for other lead-free multiferroic composites. A maximum magnetoelectric voltage co-efficient of αME ∼22.4 mVcm−1Oe−1 is obtained for the NCCFO/BCZT10 composite film. The observed results suggest that the NCCFO/BCZT composite films are potential lead-free multiferroic systems at room temperature.

High performance lead-free multiferroic composites with strong magnetoelectric coupling effect are desired to replace lead-based ceramics in multifunctional device applications due to increasing environmental issues. We report crystal structure, ferroelectric, magnetic, dielectric and magnetoelectric properties of (1-x)Ba0.85Ca0.15Ti0.90Zr0.10O3-(x)CoFe2O4 (BCTZ-CFO) lead-free composites with x = 0.1, 0.3, 0.5, 0.7 and 0.9 synthesized by chemical solution method. BCTZ power was synthesized by sol-gel method while CFO was prepared by metallo-organic decomposition (MOD) method. The XRD results confirm successful formation of the BCTZ-CFO composites without presence of any impurity phase. At room temperature, the BCTZ-CFO composites show multiferroic behavior characterized by ferroelectric and ferromagnetic hysteresis curves. The composite having 10 wt% of CFO exhibited maximum polarization, remnant polarization and coercive field of Ps ∼ 5.1 µC/cm2, Pr ∼ 1.4 µC/cm2 and Ec ∼ 11.6 kV/cm respectively. The BCTZ-CFO composite with 90 wt% of CFO incorporation exhibits improved ferromagnetic properties with Ms ∼ 32 emu/g, Mr ∼ 11.7 emu/g and Hc ∼ 504 Oe. Mӧssbauer spectra analysis show two sets of six-line hyperfine patterns for BCTZ-CFO composites, indicating the presence of Fe3+ ions in both A and B sites. Increasing BCTZ content was found to decrease the hyperfine field strength at both sites and is consistent with the decreasing magnetic moment observed for the samples. The maximum dielectric constant value e′ ∼ 678 is obtained at 1 MHz for composite with 10 wt% of CFO phase. The results indicate that the BCTZ-CFO composites are potential lead-free room temperature multiferroic systems.

The room temperature and magnetic field-dependent dielectric, impedance and magnetoelectric (ME) coupling effect of polycrystalline AFe2O4/(Pb0.80Sr0.20)TiO3 (A = Mn, Ni and Co) bi-layered composite films have been investigated. The structural and microstructural analyses using the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal the presence of homogenous growth of both tetragonal and spinel phases without any extra phase and diffusion in the AFO/PST20 bi-layered composite films. Our results show that all composite films exhibit ferroelectric as well as considerable magnetic, indicating magnetoelectric coupling effect. Our results show that the dielectric and impedance properties of AFO/PST20 bi-layered composite films can be manipulated by the magnetic field at room temperature, also indicating the existence of magnetoelectric coupling. The impedance (Z′ and Z″) Nyquist plots show distinct electrical responses with the magnetic field. The maximum magnetoelectric coefficient (α) is found to be αME∼ 239 and ∼ 195 mV/cm/Oe for the MFO/PST20 and CFO/PST20 bi-layered composite films, respectively. The above results show that the AFO/PST20 bi-layered composite films are room-temperature multiferroic material that can be potentially used in magnetoelectric devices.

Single phase multiferroics BiFeO 3 (BFO), Bi 0.99 Sm 0.01 FeO 3 (Sm1) and Bi 0.99 Sm 0.01 Fe 0.99 Co 0.01 O 3 (Sm1Co1) were successively synthesized by tartaric acid assisted sol-gel method. The X-ray diffraction patterns analyzed through Rietveld refinement method confirmed substitution driven structural distortion, which was further supported by William- Hall plot. The morphological analysis of BFO and Sm1Co1 could be effectively controlled to form nanoparticles, due to the smaller ionic radii of the dopants cations. The co-doping of Sm and Co in BFO lattice significantly enhanced the magnetic properties, with the saturation magnetization being 8.4 emu/g, which is about 20 times larger than that of pure BFO (0.40 emu/g). The decrease of Neel transition temperature and irreversible behavior of FC/ZFC curves also support improved magnetic properties. With the codoping of Sm-Co, the band gap was decreased, while interestingly, the leakage current density was significantly reduced to about 10 −7 A cm −2 . A reduction of oxygen vacancies was confirmed by XPS analysis in the case of Sm1Co1 sample. The codoping leads to improved ferroelectric properties and significant enhancement of magnetoelectric coupling coefficient (9mV/cmOe). The photocalalytic activity of Sm1Co1 enhanced significantly and about 92% degradation of methylene blue dye was achieved using this catalyst under visible light irradiation.

CoFe2O4/(Pb0.6Sr0.4)TiO3 bi-layered composite film exhibits ferromagnetic and ferroelectric responses (Ms ∼ 162 emu/cm3, Hc ∼ 1.8 kOe, 2Pr ∼ 8.6 µC/cm2 and 2Ec ∼ 634 kV/cm) at room temperature. The...

Heterostructure $$\hbox {Ba}_{0.7}\hbox {Sr}_{0.3}\hbox {TiO}_{3}$$ – $$\hbox {Ni}_{0.8}\hbox {Zn}_{0.2}\hbox {Fe}_{2}\hbox {O}_{4}$$ composite thin films grown on Pt– $$\hbox {TiO}_{2}$$ – $$\hbox {SiO}_{2}$$ – $$\hbox {Si}$$ substrate were prepared by chemical solution process, where $$\hbox {Ba}_{0.7}\hbox {Sr}_{0.3}\hbox {TiO}_{3}$$ layer grew as top/bottom while $$\hbox {Ni}_{0.8}\hbox {Zn}_{0.2}\hbox {Fe}_{2}\hbox {O}_{4}$$ layer grew as bottom/top. Structural characterization by X-ray diffraction and atomic force microscopy showed the similar crystal structure, different lattice parameters, large lattice strain and small grain size in heterostructures, whatever their deposition sequences. Such heterostructures present simultaneously ferromagnetic and ferroelectric responses at room temperature. In particular, an exceptionally large saturation magnetization was observed in one heterostructures film. The growth sequences of $$\hbox {Ba}_{0.7}\hbox {Sr}_{0.3}\hbox {TiO}_{3}$$ and $$\hbox {Ni}_{0.8}\hbox {Zn}_{0.2}\hbox {Fe}_{2}\hbox {O}_{4}$$ layers on the substrate remarkably affect the magnetic properties of the composite thin films at room temperature.

Lead (Pb) based electronic materials are facing global restriction due to the toxicity of lead. Presently, there is a need for designing and studying Pb-free thin films. In the present work, we fabricated lead-free Zr-substituted BaZr0.1Ti0.9O3 (BZT10) and BaZr0.2Ti0.8O3 (BZT20) thin films on Pt/TiO2/SiO2/Si substrates by sol-gel method using spin coating technique. The major drawback of BZT solid solutions is high processing temperature (1400 °C−1500 °C). For fabrication of micro-system devices compatible with the current complementary metal oxide semiconductor (CMOS) technology, the primary requirement is fabrication of BZT thin films at lower processing temperature. So, we have developed BZT thin films at low annealing temperature 750 °C. The prepared thin films were characterized by grazing incidence X-ray diffraction (GIXRD) and Raman spectroscopy for structural study. The phase variation from tetragonal to cubic with Zr concentration has been noticed in the structural analysis and is consistent with temperature dependent dielectric study. Surface studies of thin film are related to the functionality of thin film in various technical applications. The average grain size and root mean square (RMS) roughness were calculated from Atomic Force Microscope (AFM) images. Local elastic properties have been analyzed by force modulation mode of AFM. The ferroelectric properties of BZT thin films decrease on increasing Zr content to 20 mol%. Impedance spectroscopy analysis at different bias voltages has been carried out for these lead-free BZT thin films. The high value of dielectric constant and impedance makes BZT worthy material for many technical applications.

We prepared NiFe2O4/(Pb, Sr)TiO3 (NFO/PST) bilayer films by the chemical solution method and investigated their multiferroic, magnetoelectric and magneto-impedance properties. Multiferroic properties have been observed at room temperature. The bilayer films exhibit saturation polarization P s 26.6 μC/cm2 and saturation magnetization M s 134 emu/cm3. With increasing Sr content, M s. and P s values of the NFO/PST bilayer films decrease. The variation may be ascribed to the influence of interfacial strain and decrease in tetragonality. High magnetoelectric coupling effect has been observed in the NFO/PST bilayer films with maximum value of α E = 6.35 Vcm−1 Oe−1 measured at H DC ~ 1 kOe and f ~ 10 kHz for Sr ~ 10% (NFO/PST10). The magneto-impedance measurements establish a strong dependence on magnetic field, further confirming magnetoelectric response in NFO/PST bilayer films. An alternative approach for impedance analysis of NFO/PST10 bilayer film provides direct evidence of strain mediated magnetoelectric coupling at room temperature. The results indicate that NFO/PST bilayer films can be considered as a potential multiferroic magnetoelectric material.

MnFe2O4/(Pb0.8Sr0.2)TiO3 (MFO/PST20) heterostructured composite films with three different structures have been grown on Pt/TiO2/SiO2/Si substrates by metal–organic decomposition processing via spin coating technique. The structural analysis revealed that the crystal axes of the MnFe2O4 are aligned with those of the PST20 ferroelectric matrix with obvious interfaces and no diffusions exist in all the three composite films. These composite films exhibit simultaneously multiferroic and magnetoelectric responses at room temperature. The growth structure of MFO and PST20 layers has an effect on multiferroic and magnetoelectric coupling behaviours of the composite films. The bi- and four-layered MFO/PST20 composite films exhibit superior ferroelectric properties compared to the tri-layered film. The increasing MFO and PST20 layers in the composite films enhance ferromagnetic properties and are closely related to the strain release in MnFe2O4 phase. The MFO/PST20 bi-layered composite film shows a high m...

Nanoparticles of spinel ferrites have attracted huge interest in various technological applications due to their distinct magnetic behaviour. These magnetic nanoparticles acquire surface and finite size effects. We report an improvement of magnetic characteristics in Co 2 + substituted Mg Zn nano-ferrites synthesized by co-precipitation route. Physical properties have been investigated for Mg 0.5 Zn 0.5−x Co x Fe 2 O 4 ( x = 0, 0.125, 0.250, 0.375, 0.500) nano ferrites using XRD, FTIR, FESEM, EDS, VSM, photoluminescence and UV spectroscopy. Single phase cubical spinel structure has been observed. A phase transition from superparamagnetic to ferrimagnetic behaviour for x > 0.125 has been observed. Saturation magnetization has been found to be enhanced. Frequency dependent dielectric behaviour shows normal dispersion. Absorption spectra show a shift in position of maximum absorption towards longer wavelength with increasing Co 2+ content. Photoluminescence spectroscopy has also confirmed the red shift in band edge emission with increasing Co 2+ content. Some theoretical parameters, using proposed cation distribution, like theoretical lattice parameter, oxygen positional parameter, bond length etc., have also been calculated and found to support our experimental results.

Nickel Oxide (NiO) has been synthesized by the solution combustion technique. Ni-NiO composite ceramic was prepared and annealed at 600° C and 1000° C for 2 hours. Structural, electrical, dielectric and magnetic properties were analysed which depend upon the synthesis method. Structural properties were examined by X-Ray Diffractometer (XRD), which confirmed the purity and f.c.c. phase of Ni and Ni-NiO composite. XRD data reveals the decreases in crystallite size and increase in full width half maximum (FWHM) as the annealing temperature increases. Electrical conductivity is found to decrease from 10−2 to 10−6 (Ω−1cm−1) for Ni and Ni-NiOafter annealingtill 1000° C respectively. Dielectric constant for pure Ni is observed to be 3986 and decreased from 313.72 to 303.72 when the annealing temperature of Ni-NiO composite is increased from 600° to 1000°. High value of coercive field (54.31Oe) andremanent magnetization (1.18 emu/g) is found for Ni-NiO composite annealed at 1000° C. It is observed that better magnetic properties are achievedat higher annealing temperature for Ni-NiO composite ceramic.

Lead Free Ferroelectric Na0.5Bi0.5TiO3 (NBT) Ceramic has been synthesized using sol gel method. The prepared NBT samples have been sintered at different temperatures 850°C, 950°C, 1050°C and 1150°C to achieve best sintering temperature. Structural analyses have been carried out using XRD and FTIR measurements. XRD patterns confirm perovskite structure having rhombohedral symmetry for all samples which is also supported by characteristic absorption band at ~627cm-1 in FTIR spectra. Dielectric properties of NBT samples with frequency and temperature have been studied. NBT sample sintered at 1050°C exhibit comparatively high value of dielectric constant (ε’) and phase transition temperature (Tm). Ferroelectric properties of NBT samples have been studied at room temperature. Comparatively, better ferroelectric properties are observed for NBT sample having remnant polarization (Pr)~ 14.7 μC/cm2and coercive field (Ec)~ 26.8 kV/cm sintered at 1050°C.

(Na 0.5 Bi 0.5 ) 0.99 La 0.01 Ti 0.988 Fe 0.012 O 3 (NBLTF) ceramic has been prepared by sol–gel method without and with 10 mol% excess of Na and Bi. Structural analysis of NBLTF samples has been carried out by XRD, FT-IR and Raman spectra. X-ray diffraction patterns of NBLTF samples confirm single phase perovskite structure having rhombohedral symmetry. FT-IR and Raman spectra exhibit similar characteristic bands for both NBLTF samples which confirm the formation of perovskite structure. Comparatively high intensity and shifting of Raman bands in NBLTF sample having excess mol% of Na and Bi suggest dense crystal growth which is consistent with microstructural properties of the sample and density measurements. Bi loss during sintering process and the dense crystal growth is reported to affect the dielectric, magnetic and ferroelectric properties in synthesized samples.

Zn1−x Cr x O nanoparticles with x = 0.0, 0.01, 0.03 and 0.05 were synthesized by the sol–gel technique. Powder X-ray diffraction (XRD) studies reveal that chromium (Cr) incorporates into the ZnO crystal lattice without disturbing the parent hexagonal (wurtzite) structure. Transmission electron microscopy (TEM) measurements show that the average size of these nanoparticles is in the range 15–25 nm. Optical absorption studies show that the band gap of ZnO nanoparticles varies with Cr doping. Photoluminescence (PL) studies depict the presence of defects in Cr-doped nanoparticles. Undoped ZnO exhibits diamagnetic behavior while Cr-doped ZnO samples exhibit weak ferromagnetism to anti-ferromagnetism depending on the Cr content.

Silicon (Si) is the most commonly used substrate material for fabricating integrated circuit; Si has very little fatigue effect. In the present work we developed pure NiFe2O4 and Cu, Co substituted NiFe2O4 thin films on Si substrate by metallo-organic decomposition (MOD) method using spin coating technique. The prepared thin films were characterized by XRD and Raman spectrometer for structural and phase identification. The topography and grain distribution of the prepared samples were analyzed by atomic force microscope (AFM). Magnetic hysteresis loops were measured at 10 K and 300 K using Superconducting quantum interference device (SQUID). The magnetization and coercive field increased with Cu, Co substitution. Temperature dependent magnetization (M-T) was carried out by zero-field cooled (ZFC) and field – cooled (FC) method. ZFC measurements revels that blocking temperature of the thin films is above 350 K.

In the present work, we report on structural, dielectric, multiferroic, magnetoelectric properties and impedance spectroscopic studies of 0.20(Co 1− x Zn x Fe 2− y Mn y O 4 )–0.80(Pb 0.70 Ca 0.30 TiO 3 ) ( x = 0.4, y = 0; x = 0, y = 0.2 and x = 0.4, y = 0.2) composites. The composites were prepared by metallo-organic decomposition (MOD) route. The coexistence of a cubic spinel phase and a tetragonal phase in the composites is confirmed by the X-ray diffraction measurement. Scanning electron micrographs show well distributed ferrite and ferroelectric phases in the composites. The dielectric properties of the composites have been studied in a wide range of frequency at different temperatures. The temperature dependent dielectric properties of the composites reveal that the ferroelectric–paraelectric transition temperature lies in the range of 499–546 °C. The impedance spectroscopic measurements of the composites indicate non-Debye type dielectric relaxation. The grain and grain boundary contributions in the composites have been separated using impedance spectroscopy analysis. The magnetization hysteresis (M−H) loop of the composites shows ferrimagnetic behavior with saturation magnetization values M s ∼12–13.4 emu/g and coercive field H c ∼71–273.5 Oe. The Curie temperature of the composites as determined from the inverse susceptibility vs. temperature curves is in the range of 297–480 °C. All the composites exhibit typical ferroelectric hysteresis loops indicating the presence of spontaneous polarization. A maximum value of magnetoelectric coupling co-efficient α ∼17.4 mV/cm Oe has been observed for the composite with x = 0.4 and y = 0.

Pure ZnO and 2 % Cr-doped ZnO nanoparticles were synthesized by sol–gel technique. Powder X-ray diffraction reveals that Cr incorporates into the ZnO crystal lattice without disturbing the original hexagonal structure. Transmission electron microscopy measurements show that the average size of these nanoparticles is in the range 20–25 nm. Pure ZnO nanoparticles exhibit diamagnetism while Cr-doped ZnO exhibit saturated hysteresis loop at room temperature indicating ferromagnetic behavior. Nitrogen co-doping along with Cr in ZnO shows enhanced ferromagnetism with small antiferromagnetism.

In the present study we prepared NiFe2O4, Ni0.95Cu0.05Fe2O4and Ni0.94Cu0.05Co0.01Fe2O4thin films by metallo-organic decomposition method (MOD) using spin coating technique. The samples were characterized by XRD. XRD patterns of thin films confirmed the formation of cubic spinel structure without any secondary phase. For microstructural analysis we characterized samples by Scanning Probe Microscope (SPM). From Atomic force microscopy (AFM), we analyzed surface morphology, calculated grain size, roughness and porosity. It has been found that grain size and roughness affected by Cu, Co substitution. After this we carried out magnetic force microscopy (MFM) on the samples. Effect of substitution on magnetic grains was observed from MFM.

In this study we report the synthesis of Bi1−xInxFe1−yTiyO3 (0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.05) nanoparticles by a simple cost effective solution combustion method. Pure BFO samples shows distorted rhombohedral perovskite structure with space group R3c which is also supported by Fourier transform infrared spectra study. The codoping of In and Ti at A–B sites of BFO (BIFTO) partially distorts the crystal structure, increases the lattice strain, reduces the average particle size (14 nm), and increases the Fe3+/Fe2+ ratio which significantly affect the observed results. The saturation magnetization increases significantly upon codoping (4.60 emu/gm) by about 12 times than that of pure BFO (0.4 emu/gm). The improved ferromagnetic properties upon codoping is further manifestated in large value of linear magnetoelectric coupling coefficient (4.8 mV/cmOe) which further provides an indirect evidence for the collapse of space modulated spin structure. The activation energy increases with codoping (0.68 eV), although less than 1 eV which indicates that the conduction is still dominated by charged defects.

Multiferroic BaFe0.01Ti0.99O3 (BFT) thin films were prepared by sol–gel combined metallo-organic decomposition method using spin-coating technique with polyethylene glycol (PEG) conditions [BFT coating solution was prepared by adding PEG (in volume) 3% (BFT3) and 5% (BFT5)]. X-ray diffraction confirms the formation of polycrystalline BFT of tetragonal phase. Atomic force and scanning electron microscopy shows nanoparticles in BFT3 and nanorods in BFT5 sample. The coexistence of ferromagnetism and ferroelectricity show more enhancement in case of BFT nanorods than nanoparticles. The observed ferromagnetism depends upon the oxygen vacancy and ferroelectric polarization on nanostructures, tetragonal phase and epitaxial strain. The magnetoelectric coefficient as the function of applied dc magnetizing field under ac magnetic field 10 Oe and frequency 847 Hz is measured.

(x)CoFe2O4−(1 − x)Pb0.7Ca0.3TiO3 (CFO–PCT) magnetoelectric composites with x = 0.2, 0.4, 0.6 and 0.8 were synthesized using metallo-organic decomposition (MOD) chemical method. The structural, microstructural, dielectric, ferroelectric, magnetic and magnetoelectric properties of these composites were investigated. The structural and microstructural results indicate that CFO and PCT phases can coexist in the composite without any secondary phase. The dielectric constant and loss factor of the composites were studied as a function of frequency and temperature. The temperature dependent dielectric properties show two dielectric maxima one at below ∼385 °C and another at above ∼510 °C. The dielectric anomaly below 385 °C and that above 510 °C correspond to the transitions of ferroelectric and ferrite respectively of the magnetoelectric composites. The composites show both ferroelectric and ferromagnetic behaviors at room temperature with strong dependence on ferrite concentration. The magnetoelectric voltage coefficient increases linearly with increase in applied dc magnetic-bias field up to 8 kOe. The maximum value of the magnetoelectric (ME) voltage coefficient α ∼ 86 mV/cm Oe was measured for CFO–PCT composite having 80% ferrite content. The high ME voltage coefficient of CFO–PCT composites may be suitable for storage device applications.

Substituted lead titanate PbTi 1− x Ni x O 3 nano-particles (1 and 4 mol% Ni content) were synthesized by simple metallo-organic decomposition (MOD) method annealed at 700 °C for 3 h. Such type of doping will generally generate oxygen vacancies in the ceramic material and have application in microwave and solar cell devices. Structural properties were studied from XRD pattern and it confirms the formation of single tetragonal phase. Increased tetragonal distortion in crystal structure with the doping of Ni ions is depicted from XRD pattern and was the consequence of ionic radii mismatching between substituting atoms. Calculated average crystallite size values were 28 nm and 37 nm for PNT1 and PNT4 respectively. This pattern was supported by TEM images having a particle size 33 nm and 42 nm for PNT1 and PNT4 respectively. Absence of organic functional groups and formation of M–O bonds was illustrated from FTIR spectrum. Frequency dependent dielectric properties were studied in the range≈0.075–10 MHz at 300 K. Its results revealed the improvement in dispersion less behavior up to high frequency range∼6 MHz. The slight increase in dielectric loss value (tan δ ≈0.0011) for PNT4 attributed to occurrence of oxygen vacancies in ceramic material due to Ni doping. The temperature dependent dielectric response was measured maximum at 100 KHz. Values of DC resistivity ( ρ ) for PNT1 and PNT4 were measured 258.5 and 181.6 Ω-cm×10 9 respectively.

(PbTiO 3 ) 0.5 –(Co 0.5 Zn 0.5 Fe 2 O 4 ) 0.5 composite has been prepared by the chemical solution method using metallo-organic precursors. The composite solution has been dried at ∼300 °C and post-annealed at 700 °C for 3 h to realize ferroelectric–ferrite mixed phase. The X-ray diffraction pattern shows the formation of mixed phase of spinel and tetragonal perovskite structure in the composite without the presence of any impurity phases. The structure of the composite indicates polycrystallinity in nature. The variations of dielectric constant with frequency at room temperature and also with varying temperature at different frequencies (from 1 kHz to 1 MHz) have been studied. The multiferroic behaviour of the composite is evident from coexistence of room temperature ferromagnetism and polarization hysteresis loop in the system. For this composite, the observed value of saturation magnetization is M s ∼4 emu/g, coercive field is H c ∼164 Oe and P s ∼2.5 μC/cm 2 . The present study demonstrates the possibility of the (PbTiO 3 ) 0.5 –(Co 0.5 Zn 0.5 Fe 2 O 4 ) 0.5 system as an important multiferroic composite for wide investigation.

Bi1−xSmxFe1−yMnyO3 nanoparticles were successfully synthesized by cost effective ethylene glycol based solution combustion route. The XRD patterns confirm the formation of pure phase rhombohedral structure in BFO. The Sm and Mn co-doping at A- and B-site of BFO results in structural distortion, improves particles surface morphology and reduces the average particles size to around 15 nm. The presence of two absorption IR bands around 438 cm−1 and 558 cm−1 supports the formation of perovskite structure in co-doped sample. The saturation magnetization (Ms) increases significantly with co-doping at room temperature which is about 13 times larger than that of pure BFO, and is attributed to size effect. The hysteresis loss (coercivity) decreases with co-doping due to decrease in magnetocrystalline anisotropy. The increased value of ME coefficient at room temperature provides indirect evidence for the collapse of space modulated spin structure and subsequently improved magnetic properties of co-doped BFO.

We have studied the effect of hydrothermal conditions at constant temperature of 180 °C, varying preparation time for 15, 30 and 45 h on nanostructures of diluted magnetic semiconductor Sn0.95Co0.05O2 (SC5). X-ray diffraction pattern confirm the tetragonal SnO2 rutile phase. The transmission and scanning electron microscopy shows the resulting nanostructures i.e. nanospheres and nanorods. The proposed reaction mechanism is given. The Raman spectra show the formation of tetragonal rutile structure of SC5 nanostructures. Fourier transform infrared spectrum has been used to verify the existence of Sn–O bond. The photoluminescence spectra show that the emission spectral intensity increases gradually with decreasing grains size, increasing hydrothermal heating time of SC5 samples and exhibits an intense blue luminescence centered at a wavelength of 531 nm. The optical absorbance measurements revealed that the nanometric size of the materials influences the energy band gap. All the prepared SC5 samples exhibit room temperature ferromagnetism.

Polarization switching behaviours of polycrystalline (Pb0.60Ca0.40)TiO3 thin films deposited on Pt/Ti/SiO2/Si substrate by metallo-organic decomposition technique have been studied in detail. The switching time dependence of the polarization demonstrates the effect of charge injection on the ferroelectric properties of the film. Typically, the upper limit of the polarization switching time of these films free from charge injection is ∼20 ms. The (Pb0.60Ca0.40)TiO3 film with simple Pt top and bottom electrodes exhibits ferroelectric properties with spontaneous polarization Ps∼19 μc/cm2, remanent polarization Pr∼11.8 μc/cm2 and coercive field Ec∼167 kV/cm and fatigue free behavior up to ∼5.3 × 105 read/write cycles. Although the observed value of Ec and fatigue free behavior up to 105 read/write cycles of these (Pb0.60Ca0.40)TiO3 films are not promising for their use in memory devices, no systematic study of the polarization switching properties of (Pb0.60Ca0.40)TiO3 films has been discussed earlier in the ...

PbTiO 3 (PT) nanoparticles have been prepared by chemical route using polyvinyl alcohol (PVA) as an efficient surfactant. The effect of PVA to reduce the particle's sizes of PT has been observed. X-ray diffraction (XRD) pattern shows that the PT nanoparticles are tetragonal with distortion ratio, c/a ~1.061. The average particle's size calculated from XRD and transmission/scanning electron microscopy is ~24 nm for PT powder sintered at 700°C. The nanostructured grains were also observed in PT pellet sintered at 1000°C. The dielectric properties of PT pellet have been measured from room temperature to 200°C and in the frequency range of 0.075 to 10 MHz. The values of room temperature dielectric constant and tanδ are 117 and 0.05 respectively, measured at 0.5 MHz. It is found that the dielectric constant of PT nanoparticles can be controlled up to higher frequency region of 5 MHz.

Nanostructured (Pb1 − xSrx)TiO3 (PST) (x = 0.1, 0.2 and 0.3) thin films have been prepared by chemical solution deposition process using spin coating technique. The solution as such was deposited on Pt/Ti/SiO2/Si substrates and annealed at 650 °C/3h. Nanograins dependent dielectric properties of PST films show dielectric constant up to the higher frequency region, low losses, large tunability and phase transition at small temperature. The impedance data has been fitted by Cole–Cole model to study the effect of grain boundaries on the dielectric properties. The current–voltage characteristics have been measured to study leakage current in PST films and described by Poole–Frenkel emission model. It is suggested that the key carrier transport process in PST films is emission of electrons from a trap state near the metal–film interface into a continuum of states associated with each conductive dislocation. The activation energy value for carrier transport in PST films is obtained from temperature-dependent current–voltage characteristics.

Intrinsic magnetoelectric (ME) coupling due to anomal phase transition temperature of multiferroic Pb 1− x Sr x (Fe 0.012 Ti 0.988 )O 3 (PSFT) has been studied. The average particle size of PSFT specimens was measured from X-ray diffraction peaks and scanning electron microscopy. The ferromagnetic phase transition temperature ( T p m ) was evaluated by temperature dependent heat flow, initial permeability ( μ i ) and magnetic susceptibility ( χ ) . However, ferroelectric phase transition temperature ( T p e ) was observed from temperature dependent relative permittivity ( e ) , and dc resistivity ( ρ d c ) . The doping of Fe in PbTiO 3 (PSFT0) has greatly reduced T p e , while the doping of Sr in PSFT0 has reduced T p m . The higher frequency dependent dielectric constant is explained in terms of higher dc resistivity of the PSFT nanoparticles involving Variable-Range-Hopping (VRH) conduction. The observed VRH mechanism shows low value of activation energy (i.e., in the order of meV) of fermi gap giving large ME output.

The ferroelectric polarization switching and fatigue behavior of (Pb, Ca)TiO3 thin films with a high calcium concentration of 50% deposited by metal-organic decomposition technique have been studied. The as-grown (Pb0.5 Ca0.5)TiO3 thin films exhibit good ferroelectric properties with spontaneous polarization Ps = 12.3 , remanent polarization Pr = 6.3 and coercive field Ec = 137 kV/cm. It is found that at a high-applied voltage and switching time, charge injection influences the polarization switching behavior of the film. The film also exhibits good fatigue endurance up to ∼107 switching cycles even without the oxide electrodes.

Nanocrystalline Pb0.8Sr0.2TiO3 (PST20) thin films have been synthesized by metallo-organic decomposition (MOD) technique and deposited on Pt/Ti/SiO2/Si substrates at different annealing temperatures of 550–750 °C. The X-ray diffraction (XRD) confirms the distorted tetragonal perovskite phase in PST20 films. The average grain's size varies from 35 nm to 46 nm as the annealing temperature increases from 650 °C to 750 °C as revealed by atomic force microscopy. At 550 °C, the film shows low crystallization with incomplete perovskite structure. The study of dielectric properties of PST20 films is aimed at electrically tunable applications and to observe ferroelectric behaviors of PST20 films. The film annealed at 650 °C shows large dielectric constant and higher tunability than the films annealed at 550 °C and 750 °C. The values of dielectric constant and tan δ at 1 MHz are 272 and 0.005, respectively, and tunability is ∼66% for PST20 film annealed at 650 °C. The dispersionless dielectric properties are observed up to high frequency ∼8 MHz. The results suggest that the growth of uniform, dense and nano-sized grains in PST film makes it suitable for higher frequency device applications and electrically tunable devices.

The effect of nanosize grains to enhance dielectric tunability in chemically prepared (Pb1−xSrx)TiO3 (PST) (x=0.1 to 0.5) thin films has been observed. The grain size is evaluated from X-ray diffraction patterns and atomic force microscopy. The average grain size lies in the range of 80–23 nm with varying Sr content. The nanosize grains in the PST films control the dielectric behavior up to the higher frequency region and exhibit large tunability with low loss factor at room temperature. The current–voltage characteristics show a large tunability as electron transport takes place within a highly resistive Fermi gap.

Polycrystalline Pb1−xSrx(Fe0.012Ti0.988)O3 (0.2≤x≤0.4) (PSFT) thin films have been grown on fused quartz substrates by metallo-organic decomposition technique. The grown films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), source meter and UV–Vis–NIR spectrophotometer to determine the structural, microstructural, dc resistivity and optical properties. The XRD pattern confirmed that the PSFT films has distorted tetragonal single phase, which close to cubic at higher Sr concentration. AFM analysis revealed that the grains size reduces with increasing Sr concentration and their average values lies in the range of 26–9 nm. The higher values of dc resistivity of PSFT nano grains indicate that the transmission of light occurs within these grains up to short wavelength. The refractive index and the extinction coefficient were determined from the optical transmission spectrum in the wavelength range of 200–1100 nm and compared with that theoretically calculated, when fitted to a single oscillator model. The values of optical band gap were determined from Tauc’s extrapolation fitting and suggests that the transformation of electrons during transmission of light through local states within Fermi gap.

BiFeO3–PbTiO3(BFPTO) ferromagnetoelectric (FME) material, with improved resistivity (∼109 Ω cm) and high relative density (∼0.95) is successfully prepared by sol-gel method. The microstructures, dielectric and magnetic properties are investigated by mean of X-rays diffraction, Scanning electron microscope, impedance analyzer and Vibrating sample magnetometer. A well crystalline powder was obtained after annealing in air at 825 ∘C for 20 min. The average particle size of sample calcined at 825 ∘C is 1–2 μm. Structural transformation from rhombohedral ( x = 0.0 ) to tetragonal ( x = 0.3 ) has been revealed from XRD analysis. Dielectric constant and resistivity of BFPTO is found to be increase as the content of PbTiO3 (PTO) increase and tangent loss are reduced by increasing the content of PTO in BFPTO composites. The study of M–H curve reveals that BiFeO3 (BFO) is antiferromagnetic with small residual magnetism (0.012 emu/g) due to canting of the spin. For composites with x = 0.1 and 0.3, a large induced magnetization was observed than that of BiFeO3 single Crystal. Hence BFPTO prepared in study can be leads to ferromagnetic state that has remanent magnetization, unlike that of the earlier reported BiFeO3.

(Pb,Ca)TiO 3 (PCT) thin films have been deposited on Pt/Ti/SiO 2 /Si substrate by metal-organic decomposition (MOD) technique. The film processing parameters such as drying and annealing temperatures have been optimized to obtain good-quality PCT films. Compositional analysis of the film has been studied by X-ray photoelectron spectroscopy (XPS). The effect of the annealing temperature on the crystalline structure, microstructure and electrical properties have been investigated by X-ray diffraction, atomic force microscopy (AFM) and impedance analyzer, respectively. Amorphous PCT films form at 350 °C and crystallize in the perovskite phase following the isothermal annealing at ⩾650 °C for 3 h in oxygen ambient. Typical tetragonal structure of the PCT film is evidenced from X-ray diffraction pattern. The grain size in the PCT films increases with an increase in annealing temperature. Significant improvement in the dielectric constant value is observed as compared to other reported work on PCT films. The observed dielectric constant and dissipation factor at 100 kHz for 650 °C annealed PCT films are 308 and 0.015, respectively. The correlation of the film microstructural features and electrical behaviors is described.

Synthesis of ferroelectric (Pb1−xCax)TiO3 (PCT) thin films over Pt/Ti/SiO2/Si substrates by metallo-organic decomposition (MOD) technique using a new chemical precursor route is described. The Ca composition dependent changes in the structural, dielectric and ferroelectric properties of the PCT films have been investigated. Typical tetragonal structure of the PCT films is evidenced with Ca ≤ 40% and at higher Ca concentration ∼50% a transformation to a pseudocubic structure is observed. Dependence of the ferroelectric properties on the Ca substitution is related to the combined effect of reduction in internal stress in the films, decrease in the grain size and dielectric anisotropy.

Using standard microwave X-band technique and by following Gopala Krishna's single frequency (9.90 GHz) concentration variational method, the dielectric relaxation times (τ) and the dipole moments (μ) of dilute solution of N-methylacetamide (NMA), N-methylformamide (NMF) and NMA + NMF binary mixtures in benzene solutions have been calculated at different temperatures. The energy parameters for the dielectric relaxation process for NMA + NMF binary mixture containing 30 mol% NMF have been calculated at 25, 30, 35 and 40°C and compared with the corresponding viscosity parameters. A good agreement between the free energy of activation from these two sets of values shows that the dielectric relaxation process like the viscous flow process can be treated as the rate process. From relaxation time behavior of NMA and NMF binary mixture in benzene solution, solute–solute types of the molecular association has been proposed.

Using standard standing wave microwave X-band techniques, and by following Gopala Krishna’s single frequency (9.90 GHz) concentration variational method, the dielectric relaxation times (τ) and dipole moments (μ) of binary mixtures of different molar concentrations of ethanol (EtOH) in binary mixtures of N-methylacetamide (NMA) and ethanol in benzene solutions at 25, 30, 35 and 40 ◦C have been calculated. The activation parameters (ΔHε , ΔFε , ΔSε ) for the dielectric relaxation process of binary mixtures containing 30 mol% of EtOH have been calculated at 25, 30, 35 and 40 ◦C and compared with the corresponding viscosity parameters. A good agreement between the free energy of activation from these two sets of values shows that the dielectric relaxation process, like the viscous flow, can be treated as a rate process. From relaxation time behaviour of NMA and EtOH binary mixtures in benzene solution, solute-solute and solute-solvent types of the molecular association have been predicted.

The dielectric relaxation times τ and dipole moments μ of N-methylacetamide (NMA) mixed with N,N-dimethylformamide (DMF) in benzene solutions have been obtained using standard standing wave microwave techniques and Gopala Krishna’s single frequency (9.90 GHz) concentration variational method at 25, 30, 35, and 40 ◦C. The energy parameters (ΔHε , ΔFε , ΔSε ) for the dielectric relaxation process of mixtures with equal amounts of NMA and DMF have been calculated and compared with the corresponding energy parameters (ΔHη , ΔFη , ΔSη ) for the viscous flow. On the basis of the observations it is found that the dielectric relaxation process can be treated as a rate process like the viscous flow. Solute-solute and solute-solvent types of the molecular associations have been predicted