Dielectric Loss Values Research Articles

Nanocellulose-polysilazane single-source-precursor derived defect-rich carbon nanofibers/SiCN nanocomposites with excellent electromagnetic absorption performance

Ceramic SiCN nanocomposites modified with nanocellulose derived defect-rich carbon nanofibers (CNFs-SiCN) were developed by thermolysis of nanocelulose-polysilazane single-source precursors (SSPs). Multi-loss mechanisms (i.g. polarization loss and conductive loss) were established in the SiCN ceramic nanocomposites by employing the defect-rich structure of CNFs. Cole-Cole circle plots indicate that the CNFs-SiCN ceramics possess strong polarization capability due to the defect-rich structure of the CNFs. Dielectric loss values fitted by the Debye theory showed that the proportion of polarization loss reaches an unprecedented high value, accounting for 52.1% of the total dielectric loss. When the content of nanocellulose is 10 wt% of SSPs, the minimal reflection coefficient (RCmin) and effective absorption bandwidth (EABs) of CNFs-SiCN ceramic can reach −36.3 dB and 3.0 GHz, respectively. This work may contribute new ideas for establishing multi-loss mechanisms in ceramic-based materials, finding a new application for nanocellulose, and shaping the design of novel absorbents.

Dielectric properties and second harmonic generation of glycine doped bisthiourea cobalt and nickel malonates as new semiorganic non-linear optical materials

A new class of materials viz. glycine doped bisthiourea cobalt malonate (BTCoM-Gly) and glycine doped bisthiourea nickel malonate (BTNi-Gly) have been synthesized by simple solvent free mechanochemical method. The chemical composition was evaluated by chemical and elemental analysis. Incorporation of glycine in compound was confirmed by EDAX and FTIR techniques. FTIR studies also ascertained the coordination of metal ion to thiourea through sulphur atom. SEM images showed that both the compounds have linear array type morphology. Thermal stability of material has been investigated by TG and DTA showing BTNiM-Gly is more stable (74.85 °C). Transmittance spectra reveals that lower cut-off wavelength of BTCoM-Gly is 296 nm and that of BTNiM-Gly, 298 nm, indicating to have a good optical transmission in entire visible region, which is desired characteristic for non-linear optical (NLO) materials. The dielectric measurements of the compounds were accomplished with varying frequencies at ambient temperature. Dielectric constant and dielectric loss values of both compounds were decreased with the increase in frequency which ultimately enhanced the second harmonic generation (SHG) efficiency. The SHG conversion efficiency was measured by modified Kurtz-Perry powder technique and found to be 0.751 nm and 0.610 nm times higher than standard KDP for BTCoM-Gly and BTNiM-Gly respectively. The higher SHG conversion efficiency of the compounds illustrates non-linear optical nature of materials and their suitability for NLO applications.

Relaxor-Ferroelectric Films for Dielectric Tunable Applications: Effect of Film Thickness and Applied Electric Field.

The dielectric properties, tunability and figure-of-merit (FOM) of relaxor Pb0.9La0.1(Zr0.52Ti0.48)O3 (PLZT) films have been investigated. Dielectric measurements indicated that the dielectric constant (at zero-bias field), tunability and FOM are enhanced as the film thickness increases, which are mainly attributed to the presence of an interfacial layer near the film-electrode interface. Experimental results illustrated that a slight reduction is observed in both dielectric constant and tunability (−2%) in a wide-frequency range (10 kHz–1 MHz); meanwhile, the FOM value decreases significantly (−17%) with increasing frequency, arising from the higher dielectric loss value. The 1000-nm PLZT film shows the largest tunability of 94.6% at a maximum electric-field of 1450 kV/cm, while the highest FOM factor is 37.6 at 1000 kV/cm, due to the combination of medium tunability (88.7%) and low dielectric loss (0.0236). All these excellent results indicated that the relaxor PLZT films are promising candidates for specific applications in microwave devices.

Preparation and characterization of low-cost wollastonite and gehlenite ceramics based on industrial wastes

Eight ceramic samples were prepared from bypass cement dust and ceramic sludge. Bypass cement dust was generated during cement industries, and ceramic sludge is produced through ceramic glaze preparation. The prepared ceramic samples contained 10-80 wt% of bypass cement dust and 90–20 wt% ceramic sludge, respectively. The samples were formed in disk-shaped specimens using the uniaxial pressing (20 MPa) and sintering temperature at 1100 °C for one hour. Various techniques were used in the present work, including X-ray diffraction, FTIR, porosity, density, SEM, and dielectric determination. The obtained ceramic materials were mainly composed of wollastonite and gehlenite phases with fine coarse-grained crystals, as shown in SEM photographs. The final product possessed density values ranging from 1.280 to 1.574 g/cm3, open porosity ranging from 43.2 to 58.1% making them suitable for building materials applications. The dielectric properties, the relative dielectric constant (ε'), and dielectric loss (ε“) were measured at 200 measuring points at the range of frequency from 50 Hz to 8 MHz. The dielectric loss and dielectric constant values are relatively low (0.595 to 0.714) and (9.141–12.125) at 50 Hz, respectively, while the electric conductivity (σ) values were indicative for insulator materials (σ ≤ 10−2 µS/cm for samples CS1–Cs5) at low electric frequencies at 50 Hz, whereas referring to semiconductor materials (σ < 109 µS/cm) at the higher electric frequencies. The materials obtained from the bypass cement dust and the ceramic sludge mixtures are characterized by low dielectric constant and dielectric loss values, making them suitable for electrical and electronic industrial applications.

Investigation of Crystal Structure, Electrical and Magnetic Properties of Spinel Mn-Cd Ferrite Nanoparticles

Cd1 − xMnxFe2O4 (x = 0, 0.25, 0.5, 0.75, 1) spinel ferrite nanoparticle samples were synthesized using a flash auto-combustion technique and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). The inspection of dielectric and magnetic properties of the prepared ferrites was carried out by using broadband dielectric spectroscopy (BDS) and vibration sample magnetometer (VSM) measurements, respectively. X-ray diffraction analysis verified the formation of the main cubic phase with space group Fd3m and a decrease in lattice constants with the increase in Mn-content. FTIR study revealed the two characteristic absorption bands of spinel ferrites and their dependence on Mn-content was investigated and explained. Elastic moduli, bulk modulus, rigidity modulus, Young modulus, and calculated Debye temperature have been studied and found to decrease with the increase in Mn-content. SEM analysis revealed nanoparticles agglomeration of uniform grains with increasing in the average grain size as Mn-content increased. The VSM measurements showed an increase in saturation magnetization accompanied by a decrease in coercivity as Mn-content increased. Dielectric investigations showed very high values of permittivity and dielectric loss at lower frequencies (between 105 and 106 @ 0.1 Hz according to the manganese content) reflecting the combination of exchange of electrons between ferrous and ferric ions and ions’ transport. The ac-conductivity showed a plateau that yields the dc-conductivity at lower frequencies followed by a characteristic frequency at which it tends out to follow a power law. The relation between these two parameters confirms the empirical BNN-relation.

Electrical and magnetic properties of nanostructured Ni doped CeO2 for optoelectronic applications

Employing hydrothermal technique, undoped and nickel doped cerium oxide nanoparticles (Ni doped CeO2 NPs) are synthesized with different concentration of dopant (5 M%, 10 M% and 15 M%). Prepared samples are subjected to Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), High resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV–vis), Photoluminescence spectroscopy (PL), Vibrational sample magnetometry (VSM), Dielectric and electrical conductivity studies. Formation of CeO2 NPs and Ni doped CeO2 NPs is confirmed by PXRD and EDX. The crystallite size of the samples, determined from powder XRD using Williamson-Hall (W–H) plot, diminishes with increased Ni doping. The lattice parameter variation indicates an initial lattice contraction when the doping is less and a lattice expansion with enhanced Ni doping. These variations in crystallite size and lattice parameter could be due to the replacement of Ce ions by Ni ions in the CeO2 lattice. SEM and HRTEM images show that the morphology of the NPs formed is nearly spherical. The UV–vis spectroscopic studies indicated that bandgap energy of Ni doped CeO2 NPs widens as the Ni dopant concentration is increased. Increase of oxygen vacancy (VO) with increase in Ni concentration is designated by Raman spectra. The PL studies show that the nanoparticles of CeO2 and Ni doped CeO2 exhibit luminescence in the violet-blue-green wavelengths region (400 nm–500 nm). The decrease in emission intensity with increase of Ni concentration is indicative to increase of oxygen vacancies with increase in Ni content which act as non-radiative centers. VSM studies show that all the samples exhibit paramagnetism. The saturation magnetization and the retentivity of the samples increase as the Ni dopant concentration increases. All the samples display frequency dependent dielectric properties. With increase in the concentration of Ni dopant and frequency, a reduction in the values of dielectric constant and dielectric loss and an improvement in the electrical conductivity were observed for all the samples.

Fabrication, structural, optical, and dielectric properties of PVC-PbO nanocomposites, as well as their gamma-ray shielding capability

Physical, linear optical, dielectric spectroscopy and photon shielding competence of fabricated PVC (polyvinyl chloride) doped with xPbO nanoparticles (x = 0, 2.5, 5, 10, 15, and 25 wt%) have been investigated. The density of PVC is increased from 1.4451 to 2.1014 g cm−3 by incorporation 25 wt% of PbO. The optical band gap (Egap) decreases from 5.14 to 4.54 eV for the direct transition and from 4.50 to 3.75 eV for the indirect transition as the concentration of PbO increases. Urbach energy (Eurbach) increased from 0.198 eV for the pure PVC sample to 0.673 eV for PVC loaded with 25 wt% of PbO. Refractive index (n) increased with the increase of PbO concentration. The less dielectric constant (ε′) values of all nanocomposites were obtained than that for pure PVC. Values of dielectric loss (tan δ) for all investigated samples decreases with increasing frequency up to 50 kHz and become constant for further frequency. Both linear (LAC) and mass attenuation coefficients (MAC) values of PVC were gradually increased by increase concentration of PbO while both half value layer (HVL) and relaxation length (RL) value were gradually decreased by increase concentration of PbO. Pure PVC with density (ρ = 1.4451 g cm−3) has neutron shielding characteristics better than that obtained for PVC/25 wt% PbO with higher density (ρ = 2.1014 g cm−3). The highest ∑R is 0.06252 cm2 g−1 for pure PVC, and the lowest is 0.05003 cm2 g−1 for PVC/25 wt% PbO, in contrast. Finally, the obtained results confirm that the fabricated PVC-PbO nanocomposites can be applied in optical, electronic, and radiation shielding applications.

Broadband dielectric relaxation spectroscopy and molecular dynamics simulation study of paracetamol-propylene glycol solutions

The complex permittivity ε*(ω) = ε′(ω) - ε“(ω) was studied for a series of paracetamol (PCM) – propylene glycol (PG) solutions over the broadband frequency range of 20 Hz to 20 GHz at different temperatures ranging from 293.15 K to 323.15 K. Measurements of the complex permittivity were carried out using Agilent Precision LCR meter E4980A with Agilent 16452A liquid test fixture (for 20 Hz to 2 MHz frequency region) and Anritsu Shockline Vector Network Analyser MS46322A with DAK-3.5 probe (for 200 MHz to 20 GHz frequency region). Obtained broadband frequency dependent dielectric data were analyzed to explore the interaction mechanisms and structural behavior of PCM and PG molecules in mixed state in terms of molar PCM concentration and temperature variation. Temperature dependent dc conductivity response of all solutions exhibited Arrhenius behavior from which activation energy was calculated. Microwave complex permittivity data were fitted to the Cole-Davidson model in order to determine dipolar relaxation parameters of the solutions. Dielectric constant and dielectric loss values at a spot frequency of 2.45 GHz were utilized to determine the microwave heating parameters and analyzed in view of its suitability for the microwave dielectric heating in pharmaceuticals. Molecular dynamics simulation study for selected concentrations of PCM in PG was also conducted in order to understand the actual mechanism of H-bonding interactions in the solutions and to justify the inferences derived from the experimental results.

Sintering Temperature, Frequency, and Temperature Dependent Dielectric Properties of Na0.5Sm0.5Cu3Ti4O12 Ceramics.

NSCTO (Na0.5Sm0.5Cu3Ti4O12) ceramics have been prepared by reactive sintering solid-state reaction where the powder was prepared from the elemental oxides by mechanochemical milling followed by conventional sintering in the temperature range 1000–1100 °C. The influence of sintering temperature on the structural and dielectric properties was thoroughly studied. X-ray diffraction analysis (XRD) revealed the formation of the cubic NSCTO phase. By using the Williamson–Hall approach, the crystallite size and lattice strain were calculated. Scanning electron microscope (SEM) observations revealed that the grain size of NSCTO ceramics is slightly dependent on the sintering temperature where the average grain size increased from 1.91 ± 0.36 μm to 2.58 ± 0.89 μm with increasing sintering temperature from 1000 °C to 1100 °C. The ceramic sample sintered at 1025 °C showed the best compromise between colossal relative permittivity (ε′ = 1.34 × 103) and low dielectric loss (tanδ = 0.043) values at 1.1 kHz and 300 K. The calculated activation energy for relaxation and conduction of NSCTO highlighted the important role of single and double ionized oxygen vacancies in these processes.

Dielectric, Thermal and Water Absorption Properties of Some EPDM/Flax Fiber Composites.

This paper deals with the dielectric and sorption properties of some flax fiber-reinforced ethylene-propylene-diene monomer (EPDM) composites containing different fiber loadings as well as their behavior after exposure to different doses of electron beam irradiation. Three relaxation processes were evinced, a weak relaxation β at sub-Tg temperatures and two α-type relaxations above the Tg. The EPDM/flax composites exhibited higher values of dielectric constant, dielectric loss and conductivity as compared to a pristine EPDM sample. Using thermogravimetric analysis (TG) coupled with Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS) (TG/FTIR/MS system), the degradation products can be identified. The water uptake increased as the flax fiber level increased in composites. The water uptake tests of irradiated composites showed that the highest water content was obtained for a flax fiber level of 20 phr.

Defect engineering for reduced large AC signal dielectric loss of PZT‐based hard piezoelectric ceramics

AbstractA low dielectric loss value under large AC electric fields is highly desired for piezoelectric ceramics in high‐power applications. However, only a few reports have focused on studying or revealing the dielectric loss behavior and mechanism of piezoelectric ceramics under an AC electric field. In this work, x (Ca, Fe) co‐doped Pb0.96Sr0.04Zr0.53Ti0.47O3 (x = 0.0, 0.25, 0.5, 1.0, 1.5 mol.%) hard piezoelectric ceramics (PSZT‐xCF) were selected for investigation. The lowest dielectric loss (@ E = 500 V mm−1) was 0.8% at x = 1.5 mol.% after aging for 30 days, which was a decrease by an order of magnitude compared with the counterpart pure PSZT. The origin of ultra‐low dielectric loss was thoroughly analyzed. Combined with Rayleigh's law, we investigated the reason behind the changes in dielectric permittivity under AC electric fields with aging time. The significant reduction in the contribution of extrinsic effect of domain wall motion dominated the reduction in dielectric loss because of the introduction of defect dipoles. This work provides a fundamental understanding of low dielectric loss piezoelectric ceramics under AC electric fields for high‐power applications.

Structural, dielectric, impedance and ferroelectric properties of lead-free Bi(Fe0.85Dy0.15)O3 ceramic

Nowadays, several research groups are extensively trying to develop by synthesizing and characterizing single/co-doped single-phase bismuth ferrite (BFO) in order to get a highly efficient eco-friendly multifunctional devices. In this process, this report is an attempt to provide the detailed studies of structural, dielectric, impedance and ferroelectric properties of Bi(Fe0.85Dy0.15)O3 ceramic fabricated via the solid-state reaction method. Analysis of X-ray diffraction (XRD) data confirms a single phase of orthorhombic symmetry. The average crystallite (particle) size is found to be in the order of ~ 41 nm. The field emission scanning electron microscopy (FE-SEM) spectrum shows a homogeneous grain distribution of the sample. The elemental composition examined by means of energy dispersive X-ray spectroscopy (EDXS) shows the existence of constituent elements of the sample. The electrical measurements and analysis, carried out using a computer-controlled phase sensitive multimeter (PSM) in a frequency range of 1 kHz–1 MHz at different sets of temperature (25–325 °C), provide many interesting features to explain further conduction mechanism. The dielectric analysis exhibits high value of dielectric constant (ɛr) and small value of dielectric loss (tanδ). Due to the effect of electronic and space charge polarization, the ɛr value falls with an increasing frequency. The frequency–temperature dependence of impedance and electrical modulus analysis reveals the presence of semiconductor nature and non-Debye type of relaxation process in the sample. The analysis of ac-conductivity (σac) with respect to frequency and temperature obeys the universal Jonscher’s power law. The electric polarization study shows an enhancement in ferroelectric property of the material. Hence, based on the significant enhancement in electrical and ferroelectric properties of the Bi(Fe0.85Dy0.15)O3 material, the material may be considered for some applications.

Enhancement of Dielectric Properties via Crystal Structure and Microstructure Control in the (K0.5Na0.5)NbO3-SrTiO3 System

Solid solutions and composites of a mixture of (K0.5Na0.5)NbO3 (KNN) and SrTiO3 (ST) were respectively synthesized by different process routes using a conventional solid state reaction. All starting materials were mixed simultaneously and calcined at 800 &lt;sup&gt;o&lt;/sup&gt;C for 4 h to obtain the solid solutions of KNN-ST. Meanwhile, the composites of KNN-ST were obtained by mixing the synthesized KNN and synthesized ST, respectively. KNN-ST calcined powders were sintered at 1150, 1250 and 1300 &lt;sup&gt;o&lt;/sup&gt;C for 2 h. The calcined powders, in which all starting materials were mixed at once, showed a single-phase pseudo-cubic structure after sintering. On the other hand, the powders with the mixture of KNN and ST had two phases of cubic ST and orthorhombic KNN as composites. The dielectric loss values of all samples decreased as the sintering temperature increased because of increased densification. The dielectric constants of the solid solutions were increased as the sintering temperature increased, however, the dielectric constants of the composites decreased with increasing sintering temperature. It was concluded that, for enhanced dielectric properties, the dielectric materials should be synthesized as solid solutions.

Space charge induced augmented dielectric permittivity and improved energy harvesting ability of nano-Ag decorated ZnSnO3 filled PVDF based flexible nanogenerator

Here we report the effect of conducting Ag decoration on ZnSnO3 filler surface on the dielectric and mechanical energy harvesting performance of the resulting PVDF based composite films. The room temperature dielectric permittivity significantly enhanced for Ag@ZnSnO3 loaded PVDF compared to that of the ZnSnO3 loaded PVDF films through the effect of improved space charge polarization after Ag decoration on ZnSnO3 filler. The dielectric permittivity of the composite films was found to be increased gradually with the increase in the Ag concentration on ZnSnO3 filler surface. All the films exhibited low value of dielectric loss (˂0.05 at 10 kHz) which proved their good applicability in flexible dielectrics. The improved polarization enhanced the mechanical energy harvesting performance of the composite films. The output peak to peak open circuit ac voltage (VOC) for Ag@ZnSnO3-PVDF (5A10ZS) (with maximum Ag concentration on ZnSnO3 in the present experiment) film after repeated human finger tapping on it was found to be increased to ~ 20 V from a value of ~3.5 V and 11 V for neat PVDF and ZnSnO3-PVDF (5ZS) films, respectively. A 10 μF capacitor was charged to ~3.8 V dc after rectification of output VOC from 5A10ZS sample by 270 s of applied stress on it. During discharging, this dc electrical signal was able to light up some LEDs (connected in parallel) together instantaneously which proved the real life applicability of the nanogenerator device in self-powered flexible electronics.

Effect of concentration of Nd3+ on the photoluminescence and ferroelectric properties of Bi4-xNdxTi3O12 films

Lead-free films of Bi4-xNdxTi3O12 were deposited on Pt(111)/Ti/SiO2/Si(100) substrate via spin-coating methods. It is shown that there are no secondary phases in the films of Bi4-xNdxTi3O12 and clear interfaces between the films of Bi4-xNdxTi3O12 and substrates when the films are annealed at 700 °C. And the films of Bi4-xNdxTi3O12 also exhibit a blue light emission peak at 437 nm and a yellow light emission peak at 580 nm. There are narrower band gaps, greater values of dielectric constant and lower values of dielectric loss when the concentration of Nd3+ varies from 0 to 0.85. And the films of Bi4-xNdxTi3O12 possess the minimum of band gap energy (2.67 eV). Moreover, the films of Bi4-xNdxTi3O12 exhibit minimal leakage current density and maximal remanent polarization, which is highly beneficial for the potential applications in multi-functional devices.

Investigation of photoluminescence and dielectric properties of europium-doped LaOCl nanophosphor and its Judd–Ofelt analysis

Present Phosphor La1−xEuxOCl (0 ≤ x ≤ 0.09) was synthesized via conventional solid-state method at a temperature of 700 °C for a duration of 2 h. The compound crystallized in the tetragonal structure with space group P4/nmm (No. 129). The intensity of transition 5D0 → 7F2 (617 nm) was found to be more intense in the photoluminescence spectra. Intensity parameters and radiative properties like radiative lifetime, transition probabilities, and branching ratio are evaluated employing of the Judd–Ofelt theory. At room temperature for a frequency range of 10 Hz—8 MHz, AC conductivity, dielectric properties of La1−xEuxOCl (0.01 ≤ x ≤ 0.09) are studied. Studies indicate that above 30 kHz till100 kHz, the AC conductivity establishes slowly and at 300 kHz increases rapidly. Greater values of dielectric constant and loss were exhibited towards lower frequencies which then declined significantly with increasing frequency making the phosphor suitable for microwave device applications. The CIE color coordinates results of Eu3+-activated LaOCl phosphor (0.642, 0.358) were closer to the commercial red phosphors such as Y2O3:Eu3+(0.645, 0.347), Y2O2S:Eu3+ (0.647, 0.343) and National Television System Committee (NTSC) (0.67, 0.33) resulting in making LaOCl:Eu3+behaves as a promising material for red phosphor materials.

Fabrication of basalt cotton/polytetrafluoroethylene (BC/PTFE) composite fiberboards with excellent dielectric properties over a wide frequency range

To expand the field of application of basalt cotton (BC) and BC-based composites, BC/PTFE (polytetrafluoroethylene) composite fiberboards were prepared by embedding a PTFE filler into a BC matrix using a wet method. The mechanical and dielectric properties of the composites were investigated. The experimental results indicate that the composites prepared using a concentration greater than 4 wt% PTFE could maintain the structural stability of the fibers in BC under high stress. The dielectric constant of BC/PTFE composites exhibited good frequency stability over a wide frequency range. The PTFE filler facilitated a decrease in the dielectric constant and dielectric loss, and the dielectric loss values of all composites remained below 0.007. The dielectric constants of the BC/PTFE composites were stable over a wide temperature range, and when PTFE content increased, the constant values were large within a stable temperature range.

Facile fabrication of novel nanostructured Au@PbI2 thin films and their structure, optical and NLO studies for higher order nonlinear applications

Herein, a facile fabrication of gold (Au) doped lead iodide (PbI2) (Au@PbI2) thin films have been achieved via spin-coating process from the microwave-synthesized Au@PbI2 nanosheets for the first time. Phase was confirmed from X-ray diffraction and FT-Raman spectroscopy analyses and approved 2H-Polytype of PbI2. The grain sizes were estimated via atomic force microscopy (AFM) and noticed between 13.5 and 9.2 nm for PbI2 and Au@PbI2 sample respectively. The Au doping in PbI2 was seen in EDX spectra and its homogeneity in SEM e-mapping. The nanostructured films fabrication was confirmed by SEM/AFM images. The transmittance of grown films is quite good in the visible region and reduction was seen in Au@PbI2 film compare to pristine. The energy gaps were estimated ~2.41 eV for pure and 2.45 eV for Au@PbI2 films. The value of refractive index was noticed ~2 in lower wavelength region. Dielectric constant and loss values were also determined. The highest values of nonlinear parameters like χ1, χ1 and n2 are found to be 0.68, 3.5 × 10−11 (esu) and 4.3 × 10−10 (esu) respectively at 1.11 eV of energy.

Composition Dependent Electrical Properties of (Ba1−xCaxZr0.1Ti0.9)O3 Ceramics, Near Morphotropic Phase Boundary (0.140 ≤ x ≤ 0.160)

In this work, pellet samples of (Ba1−xCaxZr0.1Ti0.9)O3, (0.140 ≤ x ≤ 0.160) were prepared using solid-state reaction route with double sintering. The dielectric and structural properties of the prepared samples were measured, from room temperature to 250 °C, at different frequencies, in the range 10–1000 KHz. A peak shifting anomaly in the X-ray diffraction peaks patterns, an anomalous change in the slope of c/a vs x plot, and the observed minimum values of dielectric constant, loss and conductivity of the prepared compositions show a strong compositional dependent dielectric and structural properties, indicating a morphotropic phase transition type behavior, at the composition with x = 0.150.

Effect of Fe Substitution on Dielectric, Electrical and Photocatalytic Behavior of ZnO Nanoparticles

Aims: To develop a simple and cost effective synthetic strategy for the preparation of Fe substituted ZnO nanoparticles. Background: The optoelectronic, electrical, dielectric, optical and magnetic properties of nanocrystalline transition metal substituted ZnO are being explored worldwide for a variety of applications in optoelectronic devices, solar cells, transparent thin film transistors, ultraviolet photodetector, piezoelectric devices, light emitting diodes as well as in the biomedical field. Fe substituted ZnO nanoparticles are being looked upon as promising material in dilute magnetic semiconductor system. Objective: To establish chemical identity and purity in order to ensure the complete substitution of Fe3+ in ZnO lattice and study the effect of Fe substitution on dielectric, electrical and photocatalytic behavior of ZnO nanoparticles. Methods: The nearly spherical ZnO and Fe substituted ZnO nanoparticles were synthesized at a low temperature via solution combustion synthesis employing metal nitrate and sucrose. Results: The powder X-ray diffraction measurement has revealed the monophasic character and complete substitution of Fe in the wurtzitic ZnO lattice. The lattice constants and aspect ratio of Fe substituted ZnO were nearly constant and comparable to that of pristine ZnO. The average crystallite size was found to decrease with increasing Fe substitution. SEM images revealed porous spongy network like morphology. TEM measurements revealed a nearly spherical particle with narrow size distribution between 10 nm - 25 nm. Conclusion: The dielectric constant and dielectric loss decrease upto x = 0.04 and increases with further increase in Fe concentration. The lower value of dielectric loss in the higher frequency region indicates the less lossy nature of Fe substituted samples. AC conductivity behaviour suggests small polaron hopping type of conduction mechanism. The RT DC resistivity was found to decrease with increasing Fe substitution. Pristine ZnO displayed very high degradation efficiency for photodegradation of MB dye. The photodegradation efficiency was found to decrease considerably with increasing Fe substitution.