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We report the mechanism to enhance the dielectric and ferroelectric behavior of polymer-ceramic composites through surface hydroxylation of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) ceramic filler-particles embedded in PVDF-HFP copolymer matrix. Varying the hydroxylated h-(BZT-BCT) filler particle-content (φ = 0–40 wt%) in PVDF-HFP copolymer matrix, composite films (of ~75 μm thickness) were prepared. We observed that, with an increase in filler content up to an optimum concentration of 15 wt%, a microstructure with gradually denser particle-arrangement and enhanced particles-polymer surface interaction is exhibited, which leads to improved dielectric and ferroelectric behavior. The energy storage density (728 mJ/cm3 at an electric field of 750 kV/cm) of the composite with 15 wt% of h-(BZT-BCT) is found to be much higher than those of the pure BZT-BCT sample, pure PVDF-HFP copolymer and their composites. Our work demonstrates the method of enhancing the functional properties through a suitable microstructure of composite materials with surface-hydroxylation of filler particles.

Multiferroic composites are promising candidates for magnetic field sensors, next-generation low power memory and spintronic devices, as they exhibit much higher magnetoelectric (ME) coupling and coupled ordering parameters compared to the single-phase multiferroics. Hence, the 3-0 type particulate multiferroic composites having general formula (1 − Φ)[PbFe0.5Nb0.5O3]-Φ[Co0.6Zn0.4Fe1.7Mn0.3O4] (Φ = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, (1 − Φ) PFN-ΦCZFMO) were prepared using a hybrid synthesis technique. Preliminary structural and microstructural analysis were carried out using XRD and FESEM techniques, which suggest the formation of 3-0 type particulate composite without the presence of any impurity phases. The multiferroic behaviour of the composites is studied with polarization versus electric field (P-E) and magnetization versus magnetic field (M-H) characteristics at room temperature. The nature of ME coupling was investigated elaborately by employing the Landau free energy equation along with the magneto-capacitance measurement. This investigation suggests the existence of biquadratic nature of ME coupling (P2M2). The magneto-electric coupling measurement also suggests that strain mediated domain coupling between the ferroelectric and magnetic ordering is responsible for the magneto-electric behaviour. The obtained value of direct ME coefficient 26.78 mV/cm-Oe for Φ = 0.3, found to be higher than the well-known single-phase materials and polycrystalline composites.

Magnetoelectric (ME) materials exhibit interesting physics with cross coupling between ferroelectric and magnetic order parameters and thus strong potential to be utilized in memory, spintronics and other multifunctional electronic/magnetic devices. Doping of suitable transition metals in ferroelectrics can induce magnetism and ME coupling and modify the physical properties. Here, we report the structural, electronic, magnetic and ME coupling of 3.5, 5 and 7.5 mol% cobalt doped BaTiO3 (BTO) ceramics. X-ray diffraction and Raman spectroscopy indicate that the samples are single phase having a tetragonal crystal structure with P4mm symmetry. The tetragonality ratio is found to decrease with increasing cobalt content. We observed a Fano-like asymmetric peak in the [A1(LO1)] Raman mode at ∼173 cm−1 in all the cobalt doped BTO samples. The cobalt dopants are shown to be uniformly distributed throughout the surface of the samples. We observed a lowering of the ferroelectric transition temperature and increasing diffusivity parameter with increasing cobalt concentration. The electrical properties of all the samples have been investigated in detail by impedance spectroscopy and ac conductivity studies before and after the ferroelectric phase transitions. All the samples show hysteretic ferroelectric behavior with a clear saturation state that decreases with increasing cobalt content. The observed ferroelectricity in these samples is intrinsic in nature. The 3.5% cobalt doped BTO sample exhibits paramagnetic behavior whereas the 5 and 7.5% cobalt doped BTO samples show ferromagnetic ordering below 43 K. The 7.5% cobalt doped BTO samples show significant ME coupling.

This work reports on the dielectric and electrical properties of a single-phase polycrystalline pyrochlore structured Gd2Zr2O7 ceramics with a highly dense and compact microstructure. X-ray diffraction along with Raman spectroscopic studies confirmed the formation of the pyrochlore phase; while the electron microscopy investigations showed the uniformly distributed and densely packed micrometer-sized grains. The relaxation phenomena and conduction processes in Gd2Zr2O7 analyzed using complex impedance spectroscopy which showed the appearance of low-frequency dielectric dispersion suggesting the dominance of conduction by oxygen ions. Observation of double semi-circular arcs in the Nyquist plots confirms that both grains and grain boundaries contribute to the electrical impedance of Gd2Zr2O7. The temperature-dependent ac conductivity studies on Gd2Zr2O7 followed the Jonscher’s power law exhibited a strong dispersive behavior at the low temperature (

Ferroelectric ceramic–polymer composites consisting of Poly Vinyledine Fluoride–Hexa Fluoro Propylene (PVDF-HFP) as polymer host and 0.5Ba(Zr0.2Ti0.8)O3−0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) ceramics as filler were prepared using solution casting technique. These composites are characterized for structural, microstructural, vibrational, optical, dielectric and ferroelectric properties at various experimental conditions. The electroactive β phase fraction (observed from XRD and FTIR analysis) increases as the filler concentration increases up to 20 wt% of BZT-BCT and above that its value decreases. FTIR results were analyzed to understand the mechanism of enhancement of β phase by the interaction between negatively surface charged ions of filler with the CH2 dipole of polymer matrix. UV–visible spectroscopy also employed to confirm polymer–ceramic filler interaction. Variation of the dielectric constant with different filler concentrations is explained using the percolation theory. Finally, the interplay between the functional properties and the β phase is discussed in detail.

There is increasing interest in novel magnetoelectric (ME) materials that exhibit robust ME coupling at room temperature (RT) for advanced memory, energy, spintronics, and other multifunctional device applications, by making use of the ability to control polarization with a magnetic field and/or magnetization via an electric field. Obtaining ME materials with strong ME coupling, understanding the origin, and manipulating its processing along with composition to realize large ME coefficients at RT constitute an important step in multiferroic research. To address this, we have investigated the multiferroic and ME properties of Ni-doped $\mathrm{Pb}({\mathrm{Zr}}_{0.20}{\mathrm{Ti}}_{0.80}){\mathrm{O}}_{3}$ (PZT). We find that the ferroelectric $({T}_{\mathrm{C}}\ensuremath{\sim}700\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ and weak ferromagnetic (\ensuremath{\sim}602 K) phase transitions of Ni-doped PZT are well above room temperature (RT), leading to a strong ME coupling coefficient (${\ensuremath{\alpha}}_{E,31}$) of $11.7\phantom{\rule{0.16em}{0ex}}\mathrm{mV}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{--1}\phantom{\rule{0.16em}{0ex}}{\mathrm{Oe}}^{--1}$ (${H}_{\mathrm{ac}}=1\phantom{\rule{0.16em}{0ex}}\mathrm{Oe}$ and $f=1\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$). While x-ray diffraction suggests a single-phase material, high-resolution transmission electron microscopy reveals regions with and without Ni present; thus magnetoelectric coupling between two phases is possible. First-principles calculations suggest the $(\mathrm{N}{\mathrm{i}}_{\mathrm{Pb}}{)}^{\ifmmode\times\else\texttimes\fi{}}$ defect is likely to be responsible for the experimental observed magnetism and ME coupling in Ni-doped PZT. We further demonstrate that Ni-doped PZT exhibits low loss tangent, low leakage current, large saturation polarization, and weak ferromagnetism. Ultimately, our work demonstrates that Ni-doped PZT is a cost-effective RT multiferroic with strong ME coupling.

Multiferroic composites consisting of a single-phase multiferroic [0.6(PbZr0.53Ti0.47O3)-0.4(PbFe0.5Ta0.5)O3] as a matrix and a magnetostrictive phase (Co0.6Zn0.4Fe1.7Mn0.3O4) dispersed in the matrix are fabricated via hybrid synthesis technique. The structure and surface morphology studies using x-ray diffraction and field emission scanning electron microscopy techniques indicate the formation of 3-0 type particulate composites. Coexistence of soft-magnetic behavior and ferroelectric characteristics are confirmed for composites from magnetization vs magnetic field (M–H) and polarization vs electric field (P–E) measurements, respectively. Magneto-dielectric (MD) measurement shows significant changes in the dielectric properties with the application of a magnetic field, indicating the existence of strong MD behavior. The biquadratic nature of magneto-electric (ME) coupling is described by the Landau free energy equation arising from the strain transfer at the interfaces between the constituent phases. The direct magneto-electric voltage coefficient measurement also confirms very strong coupling between ferroelectricity and magnetism and supports the strain-mediated magneto-electric effect in composites. The Φ = 0.3 composite exhibits the maximum ME coefficient of 20.72 mV/cm Oe with MS = 24.62 emu/g, HC = 59.66 Oe, and piezoelectric coefficient value d33 = 19 pC/N. The strong magneto-electric effect along with low dielectric loss at room temperature in these composites suggests their suitability for multifunctional magneto-electric device applications such as magnetic sensors, etc.

Magnetoelectric (ME) heterostructures can exhibit higher magnetic and ferroelectric ordering temperatures along with large ME coupling compared to single-phase multiferroic materials. We synthesized Pb(Fe0.5Nb0.5)O3 (PFN)/Ni0.65Zn0.35Fe2O4 (NZFO)/Pb(Fe0.5Nb0.5)O3 (PFN)/Ni0.65Zn0.35Fe2O4 (NZFO)/Pb(Fe0.5Nb0.5)O3 (PFN) multilayer heterostructures having dimensions of 40/10/40/10/40 nm. High quality epitaxial growth of these heterostructures was confirmed via X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns. These nanostructures show well saturated polarization (∼52 μC cm−2) and magnetization (∼62 emu cm−3) at room temperature (RT). The magnetic and ferroelectric transitions occur well above RT. These heterostructures exhibit relaxor behavior and undergo 2nd order ferroelectric phase transition. Magnetodielectric measurements show significant coupling between the magnetic and electrical order parameters at RT. These characteristics of the heterostructures make them suitable as potential candidates for ultra-low power memory, spintronics, and different multifunctional (micro)nanoscale device applications.

Single phase polycrystalline DyMnO3 (DMO) was synthesized using acrylamide polymer gel template method. We report the structural, magnetic, specific heat and dielectric properties of DMO over wide experimental conditions. Room temperature XRD pattern shows the formation of singe phase material without any impurity. The magnetic properties such as magnetization versus temperature (M vs. T) and magnetization versus magnetic field (M vs. H) were studied around the transition temperatures region. The temperature dependent magnetization data suggest two phase transitions corresponding to the lock-in temperature below which ferroelectric ordering exist (around 19 K; Tlock) and antiferromagnetic (AFM) ordering of Dy spin (around 8 K; TN (Dy)). The magnetic hysteresis obtained were fitted to extract weak ferromagnetic (FM) and antiferromagnetic/paramagnetic (AFM/PM) contribution to the magnetic data. The order of magnetic transitions were analyzed from Arrott plot. The temperature dependent specific heat measurement shows all three phase transitions corresponding to (i) AFM ordering of Mn spin (around 38 K; TN(Mn)), (ii) Tlock transition and (iii) TN(Dy) transition. The effect of magnetic field to the transitions were studied using specific heat capacity measurement. The peak intensity of TN(Dy) decreases on the application of magnetic field whereas peak intensity of Tlock increases with increase in magnetic field in specific heat measurement. Further the third anomaly, TN (Mn) remains more or less unaffected by the application of magnetic field. The intrinsic dielectric behaviour of the material was observed up to 160 K, above this temperature there is large increase in dielectric value due to the contribution from Maxwell- Wagner polarization.

Free standing and flexible ferroelectric ceramic-polymer composites (PVDF+ ϕ wt.% of BNBT (0.94Na0.5Bi0.5TiO3-0.06BaTiO3)) with 0–3 connectivity were synthesized by solution-casting technique. Composite nature and homogeneous distribution of ceramic filler particles in PVDF were confirmed with x-ray diffraction and scanning electron microscopic analysis. The intensity ratio of β-phase with respect to α–phase i.e., I20.2°/I18.4° (obtained from XRD analysis) and the fraction of electro-active beta phase i.e., F(β)% (obtained from FTIR analysis) are enhanced with increase in filler concentrations and peaked for 35 wt% of the ceramic filler. An enhancement of the % of crystallinity (calculated from XRD analysis) has been observed with increase in the filler concentrations. The increase of the fraction of β-phase has been explained on the basis of ion (negatively charged surface ion of the ferroelectric ceramic filler) -dipole (-CH2 dipole of the polymer matrix) interactions, as evidenced from FTIR and UV-VIS absorbance spectra. Relative dielectric permittivity (dielectric constant) and ferroelectric polarization were found to be highest for the composite with 35 wt% of ferroelectric ceramic filler. Percolation theory has been successfully employed to explain the observed trend in the dielectric properties with the compositional variation. Significant enhancement in the electro active β-phase has been correlated with the improved dielectric and ferroelectric properties of the composite.

Multiferroic composites are promising candidates for magnetic field sensors, next-generation low power memory and spintronic devices, as they exhibit much higher magnetoelectric (ME) coupling and coupled ordering parameters compared to the single-phase multiferroics. Hence, the 3-0 type particulate multiferroic composites having general formula (1 − Φ)[PbFe0.5Nb0.5O3]-Φ[Co0.6Zn0.4Fe1.7Mn0.3O4] (Φ = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, (1 − Φ) PFN-ΦCZFMO) were prepared using a hybrid synthesis technique. Preliminary structural and microstructural analysis were carried out using XRD and FESEM techniques, which suggest the formation of 3-0 type particulate composite without the presence of any impurity phases. The multiferroic behaviour of the composites is studied with polarization versus electric field (P-E) and magnetization versus magnetic field (M-H) characteristics at room temperature. The nature of ME coupling was investigated elaborately by employing the Landau free energy equation along with the magneto-capacitance measurement. This investigation suggests the existence of biquadratic nature of ME coupling (P2M2). The magneto-electric coupling measurement also suggests that strain mediated domain coupling between the ferroelectric and magnetic ordering is responsible for the magneto-electric behaviour. The obtained value of direct ME coefficient 26.78 mV/cm-Oe for Φ = 0.3, found to be higher than the well-known single-phase materials and polycrystalline composites.

Background: Sickle cell disease is the commonest inherited hemoglobinopathy. There are few reports point towards decrease incidence of diabetes mellitus in sickle cell disease patients. Materials and Methods: This cross-sectional study was conducted in VIMSAR, Burla, Odisha between Nov 2014 to Oct 2016. FBS and 2 hours OGTT reports of adult sickle cell disease patients were compared with the same reports from equal no of adult persons without sickle cell disease (controls) to found out any significant difference in prevalence of diabetes mellitus in sickle cell disease patients versus controls. Results: A total of 137 adult patients of sickle cell disease out of which males were 94 (68.61%) and females were 43 (31.38%) with an average age of (26.7 ± 10.9) years and an equal number of controls [males 87 (63.8%) and females 50 (36.5%)] with an average age of (47.6 ± 13.6) years were included in the study. We found diabetes mellitus in 2 (1.46%) out of 137 sickle cell disease patients with an average BMI 18.5 kg/m2 versus 12 (8.76%) in equal number of controls with an average BMI of 22.6 kg/m2. Conclusion: This study concludes that prevalence of diabetes mellitus in sickle cell disease patients is significantly lower than non-sickle cell disease persons. This may be due to less longevity and low BMI in sickle cell disease patients.

We report the preparation of ferroelectric Ba0.7Ca0.3TiO3 (BCT) ceramics by sol–gel auto combustion technique and its specific functional properties. The structural, dielectric and ferroelectric properties of BCT are strongly depending on the sintering temperature which also improves the phase purity and crystalline quality of the system. The formation of single-phase BCT is realized by sintering at 1450 °C for 4 h. suggesting the solubility limit of Ca2+ cation. Grain size and relative density are increased as the sintering temperature increased. The Rietveld refinement technique is employed for the detailed crystal structural analysis. The temperature and frequency dependent dielectric properties are investigated; the measured dielectric constant is er = 2680 at the transition temperature Tc=120 °C for the single phase ferroelectric BCT. Sintering and electrical poling improved the shape of the hysteresis curve and reduced the leakage current. Electrical conduction mechanism is also discussed.

Varying the substrate temperature changes structural and magnetic properties of spinel ferrite Ni0.65Zn0.35Fe2O4 (NZFO) thin films. X-ray diffraction of films grown at different temperature display only (004) reflections, without any secondary peaks, showing growth orientation along the c-axis. We find an increase in crystalline quality of these thin films with the rise of substrate temperature. The surface topography of thin films grown at different growth temperatures reveal that these films are smooth with low roughness; however, the thin films grown at 800 °C exhibit lowest average and root mean square (rms) roughness among all thin films. We find iron and nickel to be more oxidized (greater Fe3+ and Ni3+ content) in films grown and annealed at 700 °C and 800 °C, compared to those films grown at lower temperatures. The magnetic moment is observed to increase with an increase of substrate temperature and all thin films possess high saturation magnetization and low coercive field at room temperature. Films grown at 800 °C exhibit a ferrimagnetic–paramagnetic phase transition well above room temperature. The observed large magnetizations with soft magnetic behavior in NZFO thin films above room temperature suggest potential applications in memory, spintronics, and multifunctional devices.

This study focuses on the effect of anatase titania acting as nanofiller on the relaxation dynamics and ionic conductivity behavior in polymer nanocomposite electrolyte based on PEO20–LiCF3SO3–TiO2. Using broadband dielectric spectroscopy, the dynamics of ion transport mechanism is studied over a wide range of temperature and frequency. Polymer salt complex exhibit the direct current (dc) conductivity σdc = 3.760 × 10–7 S cm–1 at 303 K. But with the addition of 8 wt % TiO2, a 2-order increase in the magnitude of dc conductivity is observed at the same temperature. Ion conduction mechanism is analyzed employing a complex relative permittivity as well as modulus formalisms. Isotherms of real part of conductivity spectra and dielectric loss spectra are analyzed to explain the observed first and second universalities in the ion conduction mechanism. Kramer–Kronig approach is used to discuss the crossover between the two universalities. Ratner’s classical approach in combination with modified Nernst–Einstein r...

Complex impedance spectroscopic technique has been implemented to study the detailed electrical transport properties of Lead free ferroelectric ceramic solid solutions of (1 − x) Na0.5Bi0.5TiO3–x BaTiO3 (NBT–BT) (0.00 ≤ x ≤ 0.10). The NBT–BT ceramics have been synthesized by sol–gel auto combustion method and sintered via microwave sintering technique. Room temperature X-ray diffraction patterns confirmed the formation of the single phase materials with perovskite structure. The surface morphology of the samples has been studied using field emission scanning electron microscopic (FESEM) technique. The FESEM micrographs confirm that the grain size decreases with increasing BaTiO3 (BT) concentration. Complex impedance, complex electric modulus formalism, and frequency dependent ac conductivity analysis have been used to study the relaxation and conduction mechanism in these materials. The presence of grain- and grain boundary contribution to impedance spectra in NBT–BT ceramics were analyzed using complex impedance plot in association with complex modulus plot. The grain- and grain boundary contributions were discerned in NBT–BT ceramic through least-squares fitting of the experimental data with a suitable equivalent circuit model. Complex impedance and complex electric modulus spectroscopic analysis indicate that the dielectric relaxation in these materials are of non-Debye type. A negative temperature coefficient of resistance (NTCR) behavior of our NBT–BT ceramics was seen from the temperature dependent conductivity studies. We have obtained similar activation energies from the conduction and relaxation process.

Here, we have studied the phase transition and magneto-electric properties of a 70 wt. % Pb(Fe0.5Nb0.5)O3–30 wt. % Co0.6Zn0.4Fe1.7Mn0.3O4 (70 wt. % PFN–30 wt. % CZFMO) multiferroic composite that exhibits a maximum magneto-electric (ME) coefficient of 26.78 mV/cm Oe at room temperature. Raman analysis confirms the formation of composite and development of strain with the shifting of Raman modes. The local symmetry breaking of end members of the composite is observed by the splitting of Raman modes. The first-order derivative of magnetization with temperature (dM/dT vs T) shows anomalies across 140 K due to the PFN phase, whereas the anomaly around 250 K is due to the spin glass transition of the CZFMO phase. The magnetization vs magnetic field (M–H) study at different temperatures reveals the existence of superparamagnetic behavior above 300 K. The temperature-dependent dielectric behavior of the composite shows an anomaly around ferroelectric phase transition (Tm) for the PFN phase along with the broad relaxation peak arising due to the CZFMO phase. The linear behavior of magnetocapacitance (MD%) with the square of magnetization (M2) suggests the existence of biquadratic ME coupling. The ME study on the composite suggests the existence of both direct and converse ME effects.

Single phase lead-free ferroelectric ceramic Na0.5Bi0.5TiO3 (NBT) is synthesized using sol-gel method and sintered using microwave sintering technique. The structural, microstructural, and electrical properties are investigated in detail. Rietveld refinement technique is used to analyse XRD pattern. SEM micrograph shows the densely packed micrometre sized grains. Ferroelectric hysteresis loops for unpoled and poled samples confirm its ferroelectric nature. The characteristic ferroelectric properties like remanent polarization and coercive field are found to be 84.8 mC/cm(2), 71.8 mC/cm(2) and 58.8 kV/cm, 58.6 kV/cm respectively for the unpoled and poled samples. The current versus voltage curve of the NBT follow the bulk-limited space-charge conduction mechanism.

We report the structural and magneto-dielectric properties of 0.95 Pb(Fe0.5Nb0.5)-0.05 Co0.6 Zn0.4Fe1.7Mn0.3O4 (0.95PFN-0.05CZFMO, PC5) particulate composite prepared using a hybrid synthesis technique. Rietveld refinement on the XRD patterns of the end compounds i.e. PFN and CZFMO were performed using monoclinic crystal structure with space group Cm and cubic crystal structure with space group Fd-3m respectively. The dual phase space group Cm+Fd-3m was taken to refine the XRD pattern of PC5 sample which confirms the formation of composite. The changes in the dielectric parameters by the application of magnetic field suggest existence of magneto-electric coupling behavior in the composite at room temperature (RT). The quantitative changes of the magneto-dielectric properties i.e. MC% (magneto- capacitance), ML% (magneto-loss), MI% (magneto-impedance) and MP% (magneto-phase) were calculated and discussed their dependence with magnetic fields at RT.

The physical and chemical properties of soft polymer–ceramic composites with 50 MeV swift heavy, Li3+ ion irradiation were studied. A solution-casting technique was employed to synthesize free standing, flexible composite films of ferroelectric polymer PVDF and ferroelectric ceramic BNBT mixtures with 0–3 connectivity. However, only 35 wt% ceramic was chosen for the study as it showed the highest dielectric constant and enhanced ferroelectric properties without irradiation. The effects of ion irradiation on the structural, microstructural, morphological, dielectric and ferroelectric properties of this particular composition were systematically investigated and conclusions were drawn. The mechanism for the enhancement of the electroactive β-phase due to the swift heavy ion irradiation was discussed and the enhancement was well correlated with its ferroelectric and dielectric properties.

Multiferroic composites with enhanced magneto-electric coefficient are suitable candidates for various multifunctional devices. Here, we chose a particulate composite, which is the combination of multiferroic (PbFe0.5Nb0.5O3, PFN) as matrix and magnetostrictive (Co0.6Zn0.4Fe1.7Mn0.3O4, CZFMO) material as the dispersive phase. The X-ray diffraction analysis confirmed the formation of the composite having both perovskite PFN and magnetostrictive CZFMO phases. The scanning electron micrograph (SEM) showed dispersion of the CZFMO phase in the matrix of the PFN phase. The temperature-dependent magnetization curves suggested the transition arising due to PFN and CZFMO phase. The temperature-dependent dielectric study revealed a second-order ferroelectric to the paraelectric phase transition of the PFN phase in the composite with a small change in the transition temperature as compared to pure PFN. The magnetocapacitance (MC%) and magnetoimpedance (MI%) values (obtained from the magneto-dielectric study at room temperature (RT)) at 10 kHz were found to be 0.18% and 0.17% respectively. The intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm−1Oe−1, which is comparable to other typical multiferroic composites in bulk form. The composite PFN-CZFMO exhibited a converse magneto-electric effect with a change in remanent magnetization value of −58.34% after electrical poling of the material. The obtained outcomes from the present study may be utilized in the understanding and development of new technologies of this composite for spintronics applications.

The conduction mechanism of polymer nano-composite electrolytes are studied using broadband dielectric spectroscopy over a wide range of frequency and temperature. The polymer nano-composites consisting of polyethylene oxide as polymer host, lithium trifluoromethanesulfonate as salt, and nano-crystalline zirconia as filler are prepared using solution casting method. Formation of polymer salt complex and nano-composites are confirmed from x-ray diffraction studies. The electrical conductivity and relaxation phenomena of the polymer salt complex as well as the composites are studied using broadband dielectric spectroscopy. At room temperature, the dc conductivity of the polymer nano-composites are found higher by two orders of magnitude than that of corresponding polymer salt complex. Temperature dependence of dc conductivity is following Vogel-Tamman-Fulcher trend, suggesting strong coupling between ionic conductivity and segmental relaxation in polymer electrolytes. Relaxation phenomena are studied with dielectric and modulus formalism. Frequency dependent ac conductivity show universal dielectric response and nearly constant loss features at high and low temperature regions respectively. The origin of universal dielectric response and nearly constant loss are analysed and discussed using different approaches. Kramer - Kronig approach suggests the origin of nearly constant loss is due to caged ion dynamics feature.

We report on structural, microstructural, spectroscopic, dielectric, electrical, ferroelectric, ferromagnetic, and magnetodielectric coupling studies of BiFeO3–GdMnO3[(BFO)1–x –(GMO) x ], where x is the concentration of GdMnO3 (x = 0.0, 0.025, 0.05, 0.075, 0.1, 0.15, and 0.2), nanocrystalline ceramic solid solutions by auto-combustion method. The analysis of structural property by Rietveld refinement shows the existence of morphotropic phase boundary (MPB) at x = 0.10, which is in agreement with the Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) studies. The average crystallite size obtained from the transmission electron microscopy (TEM) and x-ray line profile analysis was found to be 20–30 nm. The scanning electron micrographs show the uniform distribution of grains throughout the surface of the sample. The dielectric dispersion behavior fits very well with the Maxwell-Wagner model. The frequency dependent phase angle (θ) study shows the resistive nature of solid solutions at low frequency, whereas it shows capacitive behavior at higher frequencies. The temperature variation of dielectric permittivity shows dielectric anomaly at the magnetic phase transition temperature and shifting of the phase transition towards the lower temperature with increasing GMO concentration. The Nyquist plot showed the conduction mechanism is mostly dominated by grains and grain boundary resistances. The ac conductivity of all the samples follows the modified Jonscher model. The impedance and modulus spectroscopy show a non-Debye type relaxation mechanism which can be modeled using a constant phase element (CPE) in the equivalent circuit. The solid-solutions of BFO-GMO show enhanced ferromagnetic-like behavior at room temperature. The ferroelectric polarization measurement shows lossy ferroelectric behavior. The frequency dependent magnetocapacitance and magnetoimpedance clearly show the existence of intrinsic magnetodielectric coupling. The (BFO)1–x –(GMO) x solid solutions with x = 0.025–0.075 show significantly higher magnetocapacitance and magnetoimpedance compared to the pure BFO.

Magnetoelectric (ME) composite thin films are promising candidates for novel applications in future nanoelectronics, spintronics, memory, and other multifunctional devices as they exhibit much higher ME coupling and transition temperatures (Tc) than well-known single phase multiferroics discovered to date. Among the three types of multiferroic composite nanostructures, (2–2) layered and (1–3) vertically aligned composite nanostructures exhibit comparatively smaller ME coupling due to different shortcomings that restrict their use in many applications. Here, we study the morphological, piezoresponse force microscopic (PFM), ferroelectric, magnetic, and magnetodielectric properties of 0–3 [magnetic nanoparticles (0) homogeneously distributed in ferroelectric matrices (3)] multiferroic composite thin films. The Pb(Fe0.5Nb0.5)O3 (PFN)–Ni0.65Zn0.35Fe2O4 (NZFO) particulate composite films were synthesized by pulsed laser deposition. These particulate composite thin films are completely c-axis oriented with very low surface roughness. We observed magnetic and ferroelectric Tc above room temperature (RT) for all composite thin films. The PFN–NZFO 0–3 composites exhibit large polarization, high saturated magnetization with low coercive field, and low dielectric loss along with magnetodielectric coupling at RT. These nanocomposites might be utilized in next generation nano/microelectronics and spintronic devices.

We report the structural, magnetic and dielectric properties of lightly Gd-substituted DyMnO3 (Dy0.95Gd0.05MnO3) prepared by acrylamide polymer gel template method. Rietveld refinement on powder X-ray diffraction (XRD) data were carried out using orthorhombic crystal structure with Pnmaspace group, which suggest the formation of single phase material. The temperature dependence magnetic susceptibility data indicates the existence of antiferromagnetic transition due to rare-earth ion and lock-in transition temperature. The magnetic properties study reveal the signature of antiferromagnetic behavior along with the existence of weak ferromagnetic component in low temperature region. The intrinsic dielectric behavior of the material was observed up to 160 K and above 160 K there is large increase in dielectric behavior, which may be due to contribution from extrinsic Maxwell-Wagner polarization phenomena.

Lead-free ferroelectric 0.7Ba(Zr0.2Ti0.8)O3-0.3(Ba0.7Ca0.3)TiO3 (BZT-BCT) ceramics have been prepared by sol-gel auto combustion technique. XRD pattern reveals the realization of single phase material. Rietveld refinement of the XRD patterns confirms the rhombohedral structure having space group R3m. FESEM micrograph shows a highly dense microstructure. The effect of electrical poling on ferroelectric properties and leakage current behavior discussed in detail. The variation of leakage current with the electric field is in consistent with the space charge conduction mechanism.

Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of well-regulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1 - x) Na

Multiferroic materials have attracted considerable attention as possible candidates for a wide variety of future microelectronic and memory devices, although robust magnetoelectric (ME) coupling between electric and magnetic orders at room temperature still remains difficult to achieve. In order to obtain robust ME coupling at room temperature, we studied the Pb(Fe0.5Nb0.5)O3/Ni0.65Zn0.35Fe2O4/Pb(Fe0.5Nb0.5)O3 (PFN/NZFO/PFN) trilayer structure as a representative FE/FM/FE system. We report the ferroelectric, magnetic and ME properties of PFN/NZFO/PFN trilayer nanoscale heterostructure having dimensions 70/20/70 nm, at room temperature. The presence of only (00l) reflection of PFN and NZFO in the X-ray diffraction (XRD) patterns and electron diffraction patterns in Transmission Electron Microscopy (TEM) confirm the epitaxial growth of multilayer heterostructure. The distribution of the ferroelectric loop area in a wide area has been studied, suggesting that spatial variability of ferroelectric switching behavior is low, and film growth is of high quality. The ferroelectric and magnetic phase transitions of these heterostructures have been found at ~575 K and ~650 K, respectively which are well above room temperature. These nanostructures exhibit low loss tangent, large saturation polarization (Ps ~ 38 µC/cm2) and magnetization (Ms ~ 48 emu/cm3) with strong ME coupling at room temperature revealing them as potential candidates for nanoscale multifunctional and spintronics device applications.

We show the ability to map the phase diagram of a relaxor-ferroelectric system as a function of temperature and composition through local hysteresis curve acquisition, with the voltage spectroscopy data being used as a proxy for the (unknown) microscopic state or thermodynamic parameters of materials. Given the discrete nature of the measurement points, we use Gaussian processes to reconstruct hysteresis loops in temperature and voltage space, and compare the results with the raw data and bulk dielectric spectroscopy measurements. The results indicate that the surface transition temperature is similar for all but one composition with respect to the bulk. Through clustering algorithms, we recreate the main features of the bulk diagram, and provide statistical confidence estimates for the reconstructed phase transition temperatures. We validate the method by using Gaussian processes to predict hysteresis loops for a given temperature for a composition unseen by the algorithm, and compare with measurements. These techniques can be used to map phase diagrams from functional materials in an automated fashion, and provide a method for uncertainty quantification and model selection. The functional response of piezoelectrics for arbitrary compositions and conditions cannot be fully obtained using local probes. Although the ferroelectric to paraelectric phase transition temperature can be measured, this is only for a limited number of data points. Now, a team led by Rama Vasudevan at Oak Ridge National Laboratory and colleagues in Puerto Rico, the United States, and India demonstrate that machine learning can be used to obtain the full ferroelectric phase diagram, with functional response. From measurements on four samples of a material, they use a machine-learning technique called Gaussian processes to reconstruct piezoelectric properties for continuously varying voltages and temperatures, which with more commonly used approaches accurately predicts ferroelectric phase diagrams. This could be used to generate piezoelectric phase diagrams, highlighting material compositions with optimal properties that can then be targeted by synthesis.

We report studies of the ferroelectric and magnetic phase transitions of (1 – x)Pb(Fe0.5Nb0.5)O3 – xCo0.65Zn0.35Fe2O4 (x = 0.2) composite with emphasis upon the nature of magnetoelectric coupling at room temperature. The presence of all cationic elements with their required stoichiometry have been confirmed by SEM and XPS studies. The composite shows well-saturated ferroelectric and ferromagnetic (multiferroic) behavior at room temperature. A ferroelectric-paraelectric phase transition has been confirmed from the temperature dependent dielectric spectra along with DSC and Raman spectroscopic studies. Antiferromagnetic, ferromagnetic, and relaxor paramagnetic states have been observed in this composite. This composite shows strong bulk biquadratic magnetoelectric coupling at room temperature, which can be useful for potential multifunctional device applications.

Nanocrystalline orthorhombic gallium ferrite (GFO) has been synthesized by a sol–gel method. The synthesized powder has been characterized by TG/DTA, XRD, TEM, FTIR and nitrogen adsorption isotherm. In the present study we report an excellent ethanol vapour sensitivity of nanocrystalline GaFeO 3 at concentrations down to 1 ppm making the sensors suitable for application in food industries. Interestingly in contrast to the market available consumers breath analyser based on tin dioxide, GaFeO 3 -based sensor is immune to moisture (present in breath) and acetone vapour (an interfacing agent for diabetics). Such gallium ferrite based sensors can be used to make potential interference free breath analyser for real-life applications. In addition, such sensors being highly selective and do not show any cross-sensitivity towards moisture, methanol and carbon monoxide like those based on tin dioxide.

The present study discusses about the preparation and characterization (thermal, mechanical, and electrical) of the genipin-crosslinked gelatin emulgels. Emulgels have gained importance in recent years due to their improved stability than emulsions and ability to control the drug release. Mustard oil was used as the representative oil. A decrease in the enthalpy and entropy of the formulations was observed with the increase in the oil fraction. The mechanical studies suggested formation of softer emulgels as the oil fraction was increased. As the proportion of the oil fraction was increased in the emulgels, there was a corresponding increase in the impedance. The drug release properties from the emulgels were also studied. Ciprofloxacin was used as the model antimicrobial drug. The drug release was higher from the emulgels whose electrical conductivity was higher.

Conductivity relaxation using modulus formalism has been used to explore the coupling of ionic conductivity to dielectric relaxation in polymer electrolyte based on polyethylene oxide complexed with various content of LiAsF6. The temperature dependence of conductivity followed the VTF behavior suggesting close correlation between conductivity and the segmental relaxation process in polymer electrolytes. The coupling of conductivity to the segmental process has been discussed in terms of coupling index. For all compositions studied, the coupling index was within the range of 1–11 in the temperature range of investigation, which was in agreement with the coupled systems.

A solution casting method was successfully used to realize polymer nanocomposite electrolytes consisting of polyethylene oxide as polymer host, lithium hexafluoroarsenate as salt, and dodecylamine modified mont- morillonite clay as filler. Structural studies confirm the inter- calation of polymer-salt complex into the silicate layers of the clay and lithium hexafluoroarsenate salt solvate very well in polyethylene oxide matrix. The electrical conductivity of the polymer-salt-clay composite was higher by more than one order of magnitude than that of the corresponding polymer- salt complex at ambient temperature. Temperature depen- dence of the conductivity was studied using broadband di- electric spectroscopy, it followed Vogel-Tamman-Fulcher trend, which suggests strong coupling between ionic conduc- tivity and segmental relaxation in polymer electrolytes. This phenomenon is correlated with coupling index. Relaxation processes are studied using both dielectric and modulus for- malisms. Additionally, conductivity spectra showed nearly constant loss and universal Jonscher's power law at low and high temperatures, respectively. Crossover from nearly con- stant loss to ion hopping conductivity region is also observed.

Preparation and characterization of soy lecithin (SL) and palm oil (PO) based organogels have been reported in this study. The optimization of the composition of the organogels was carried out by varying the proportions of SL, PO and water. Microscopic studies suggested the presence of aqueous phase either as spherical droplets or fluid filled fibers or both, depending on the composition of the organogels. FTIR study indicated strong intermolecular hydrogen bonding among the organogel components. The release of metronidazole (model drug, MZ) suggested diffusion mediated drug release. MZ loaded organogels showed good antimicrobial property against B. subtilis and E. coli.

Sols of starches have been reported to form phase-separated systems when mixed with the gelatin solution. This has been attributed to the thermodynamic incompatibility of the starch-gelatin systems. The current work has been designed to study the effect of processed starches on the properties of the gelatin-starch based phase-separated physical hydrogels. The hydrogels were prepared using corn starch, soluble starch and boiled starch. The hydrogels were characterized by FTIR spectroscopy, thermal studies, textural studies and impedance spectroscopy. Metronidazole was incorporated within the hydrogels. The drug-loaded gels have shown good antimicrobial activity against Escherichia coli and Bacillus subtilis.

A series of lead-free perovskite solid solutions of (1 − x) Na0.5Bi0.5TiO3(NBT)—x BaSnO3(BSN), for 0.0 ≤ x ≤ 0.15 have been synthesized using a high-temperature solid-state reaction route. The phase transition behaviors are studied using dielectric and Raman spectroscopic techniques. The ferroelectric to relaxor phase transition temperature (TFR) and the temperature corresponding to maximum dielectric permittivity (Tm) are estimated from the temperature-dependent dielectric data. Dielectric studies show diffuse phase transition around ~335°C in pure NBT and this transition temperature decreases with increase in x. The disappearance of x-dependence of A1 mode frequency at ~134 cm−1 for x ≥ 0.1 is consistent with rhombohedral-orthorhombic transition. In situ temperature dependence Raman spectroscopic studies show disappearance and discontinuous changes in the phonon mode frequencies across rhombohedral (x

Bacterial vaginosis (BV) is a condition often associated with the overgrowth of pathogenic microbes with a subsequent decrease in lactic acid producing bacteria in vagina. BV is predominant in reproductive women. It has been reported not only to cause pre-term labor but is also one of the major causes of fetal morbidity and mortality. There is an increase in the vaginal discharge in BV. Due to this reason, the locally applied drug formulations are quickly washed off. It is expected that the mucoadhesive delivery vehicles will improve the bioavailability of the drug for prolonged periods. Keeping this in mind, gelatin/PEG based composite hydrogels were developed and characterized as vaginal delivery systems for the treatment of BV. The hydrogels were prepared by varying the concentration of gelatin and PEG. The hydrogels were thoroughly characterized using SEM, FTIR, DSC, and impedance spectroscopy techniques and swelling, mucoadhesive, and texture analysis studies. The in vitro release behavior of metronidazole from the hydrogels was analyzed in-depth. The antimicrobial efficiency of the MZ-loaded hydrogels was tested against E. coli, occurrence of which is predominant in BV. The properties of the hydrogels were found to be dependent on the composition of the hydrogels. The hydrogels were found to be mucoadhesive and the MZ-loaded hydrogels have shown effective antimicrobial activity against E. coli. Based on the preliminary studies, the composite hydrogels were found to be suitable for controlled drug delivery for vaginal applications.

Preliminary structural and detailed dielectric and electrical properties of zirconium (Zr) modified-sodium bismuth titanate (i.e., Na 0.5 Bi 0.5 Ti 1− x Zr x O 3 (NBZT)) ceramics were studied. Structural analysis of the materials with room temperature X-ray diffraction data confirmed the formation of compounds in the rhombohedral crystal system. SEM micrographs of the compounds showed the abnormal grain growth but with better densification and homogeneity on substitution of Zr at the Ti site. Dielectric and complex impedance spectroscopic studies were carried out in a wide frequency (i.e., 10 2 –10 6 Hz) and temperature (30–500 °C) range. The maximum permittivity (at transition temperature) was found to be decreased on increasing Zr concentration in NBZT but the diffuseness of dielectric peak increases. The nature of frequency dependence of ac conductivity of NBZT follows the Jonscher power law, and calculated dc conductivity follows Arrhenius behavior. Detailed studies of complex impedance spectroscopy have provided better understanding of: (i) relaxation process and (ii) microstructure-properties relationship in the materials. Complex impedance and modulus spectra confirm the significant contribution of both grain and grain boundary to electrical response of the materials. It is observed that relaxation processes in the materials are of non-Debye type.

The study has been designed to develop and evaluate the in vitro sustained-release capability of sorbitan monopalmitate (SMP) and castor oil (CO) based organogels. Organogels were prepared by heating the mixture of SMP-CO at 60°C either with or without using distilled water (DW). The heated mixture was subsequently cooled to room-temperature to allow the formation of a gelled structure. Characterization of organogels was carried out by microscopy (light, fluorescent, electron, and atomic force), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), rheological study, pH, impedance spectroscopy, hemocompatibility, and antimicrobial studies. The properties and stability of the gels was dependent on the composition of the organogels. FTIR studies indicated the presence of strong intramolecular/intermolecular hydrogen bonding amongst the gel components. XRD studies suggested amorphous behavior of the gels. The gels showed a shear thinning behavior. Metronidazole (MZ) loaded gels showed good antimicrobial property to be used as an antimicrobial formulation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1503–1515, 2013

Multiferroic composite structures, i.e., composites of magnetostrictive and piezoelectric materials, can be envisioned to achieve the goal of strong room-temperature ME coupling for real practical device applications. Magnetic materials with high magnetostriction, high Neel temperature (TN), high resistivity and large magnetization are required to observe high ME coupling in composite structures. In continuation of our investigations on suitable magnetic candidates for multiferroic composite structures, we have studied the crystal structure, dielectric, transport, and magnetic properties of Co0.65Zn0.35Fe2O4 (CZFO). Rietveld refinement of X-ray diffraction patterns confirms the phase purity with a cubic crystal structure with the (Fdm) space group; however, we have found a surprisingly large magneto-dielectric anomaly at the Neel temperature, unexpected for a cubic structure. The presence of mixed valences of Fe2+/Fe3+ cations is probed by X-ray photoelectron spectroscopy (XPS), which supports the catonic ordering-mediated large dielectric response. Large dielectric permittivity dispersion with a broad anomaly is observed in the vicinity of the magnetic phase transition temperature (TN) of CZFO suggesting a strong correlation between dielectric and magnetic properties. The evidence of strong spin-polaron coupling has been established from temperature dependent dielectric, ac conductivity and magnetization studies. The ferrimagnetic–paramagnetic phase transition of CZFO has been found at ∼640 K, which is well above room temperature. CZFO exhibits low loss tangent, a high dielectric constant, large magnetization with soft magnetic behavior and magnetodielectric coupling above room temperature, elucidating the possible potential candidates for multiferroic composite structures as well as for multifunctional and spintronics device applications.

A series of ion conducting polymer–clay composites has been prepared using a solution casting technique. Relaxation dynamics and the ionic transport mechanism are systematically studied employing broadband dielectric spectroscopy over a wide frequency and temperature range. Among different phenomenological and theoretical models for ion conduction in disordered ionic conductors, conductivity isotherm spectra are analysed using the modified Almond–West and random free energy barrier model. Conductivity scaling suggests that the ionic transport mechanism is independent of temperature, and a similar inference is also obtained using scaled electrical modulus spectra. DC conductivity along with conductivity and segmental relaxation time following the Vogel–Tammann–Fulcher relationship suggests coupling between the ionic transport and segmental relaxation processes. Electrical modulus and dielectric formalism are used to understand the conductivity and segmental relaxation processes, respectively. The presence of first and second universality in the ionic transport mechanism is discussed using the real part of conductivity spectra and dielectric loss spectra. The crossover between the first and second universality is explained using the Kramer-Kronig approach. The ion diffusion coefficient is investigated using Ratner's classical approach in combination with the modified Stokes–Einstein relationship to correlate the coupled nature of the ion conduction mechanism and polymer segmental motion.

Bismuth ferrite is doped with a dilute concentration of cobalt, BiFe1� X CoX O3 ;X ¼ 0, 0.01, 0.02 is prepared by sol-gel auto combustion technique. X-ray diffraction data refined via Reitveld method shows single phase and shrinkage in cell volume for Co doped BiFeO3. Various magnetic ground states viz. superparamagnetic, glassy antiferromagnetic and glassy ferrimagnetic behavior is observed for X¼ 0, 0.01, 0.02, respectively. A first-order magnetic transition is observed in the Arrott plot data of cobalt doped BiFeO3. Possibility of thermally induced magnetic transition is also seen in the magnetization data of cobalt doped BiFeO3. A model based on the existing spinoidal cyclic arrangement of spins is proposed to explain the observed data. Finally, a very dilute concentration of Co þ 3 in BiFeO3 is found sufficient to tailor the magnetic properties.