Narrow Results

The primary aim of the current research is to explore the impact of yttrium-doping in barium stannate titanate (Ba${}_{1-1.5x}$Y_xTi${}_{1-z}$Sn_zO₃) to investigate the variation in its structural and electrical properties. The specimens were synthesized using a solid-state method, wherein the precursors were heated together until they reacted to form the desired compounds. Subsequently, X-ray diffractometric analysis was employed to confirm the crystallographic phases. Archimedes’ method was used to determine the density of the material. An Electron Paramagnetic Resonance (EPR) study was conducted to examine the nature of defect centers and impurity ions within the synthesized ceramics. Furthermore, the impact of yttrium (Y) substitution on the system’s morphology and grain growth was evaluated through SEM micrographs. Selective compositions were found with enhanced dielectric properties of barium titanate ceramic, exhibiting a dielectric constant of 9816 at the transition point. The highest value among all studied samples had a clear indication of DC conductivity. Piezoelectric coefficient (d${}_{33}$) and P-E hysteresis loops were also investigated for these samples, indicating potential applications in electronic devices for the modified material’s improved ferroelectric properties.

The challenges in productivity of satellite mobile devices are growing rapidly to overcome the question of miniaturization. The intention is to supply the electrical and microwave properties of materials by discovering their outstanding electronic properties. Neodymium Zinc Titanate (NZT) can be a promising ferroelectric material due to its stable dielectric and microwave properties. The grain size and shape of NZT have a strong influence on overall material performances. Therefore, shape, reconstruction and property of the coming compound take an important part and can be predicted before being utilized in the devices. The significant of this research is to define ferroelectric properties of NZT and to characterize it by using Fractal Nature Analysis (FNA). FNA is a powerful mathematical technique that could be applied to improve the grain shape and interface reconstruction. The fractal structure is identified by its self-similarity. The self-similarity of an object means a repetition of shapes in smaller scales. A measure of this structure is computed using the Hausdorff dimension. It is for the first time in this investigation the Fractal analysis method is applied for the microwave materials microstructure reconstruction which makes this research an innovative work and will open the door for Curie–Weiss law fractal correction. In connection to our previous research for dielectric properties fractalization, we had some characterization and reconstruction data which include the Hausdorff dimension (HD).

Temperature and electric field dependences of the dielectric behavior and phase transition for [111]-oriented 0.23PIN–0.52PMN–0.25PT (PIN-PMN–0.25PT) and 0.24PIN–0.43PMN–0.33PT (PIN–PMN–0.33PT) single crystals were investigated over a temperature range from -100°C to 250°C using field-heating (FH) dielectric measurements. The transition phenomenon from ferroelectric microdomain to macrodomain was found in rhombohedra (R) phase region in the single crystals under dc bias. This transition temperature T_f of micro-to-macrodomain is sensitive to dc bias and move quickly to lower temperature with increasing dc bias. The phase transition temperatures in the two single crystals shift toward high temperature and the dielectric permittivities at the phase transition temperature decrease with increasing dc bias. Especially, the phase transition peaks are gradually broad in PIN–PMN–0.33PT single crystal with the increasing dc bias. Effects of dc bias on the dielectric behavior and phase transition in PIN–PMN–PT single crystals are discussed.

Yttrium Copper Titanate (Y_2/3Cu₃Ti₄O₁₂) nanoceramic is structurally analogous to CaCu₃Ti₄O₁₂ (CCTO). X-ray diffraction (XRD) of Y_2/3Cu₃Ti₄O₁₂ (YCTO) shows the presence of all normal peaks of CCTO. SEM micrograph exhibits the presence of bimodal grains of size ranging from 1–2 μm. Bright field TEM image clearly displays nanocrystalline particle which is supported by presence of a few clear rings in the corresponding selected area electron diffraction (SAED) pattern. It exhibits a high value of dielectric constant (ε′ = 8434) at room temperature and 100 Hz frequency with characteristic relaxation peaks. Impedance and modulus studies revealed the presence of temperature-dependent Maxwell–Wagner type of relaxation in the ceramic.

Breakthroughs can be expected in multi-component ceramics by adjusting the phase assembly and the micro–nanostructure. Controlling the architecture of multi-materials at different scales is still challenging and provides a great opportunity to broaden the range of functionalities in the field of ferroelectric-based ceramics. We used the potentialities of Spark Plasma Sintering (SPS) to control a number of key parameters regarding the properties: anisotropy, interfaces, grain size and strain effects. The flexibility of the wet and supercritical chemistry routes associated with the versatility of SPS allowed designing new ferroelectric composite ceramics at different scales. These approaches are illustrated through various examples based on our work on ferroelectric/dielectric composites.

xPb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(xPIN–yPMN–zPT) ternary ceramics with morphotropic phase boundary (MPB) composition were synthesized by columbite precursor method. xPIN–yPMN–zPT phase diagram was investigated by x-ray diffraction and dielectric measurements. According to the results of dielectric measurements, the Curie temperatures (T_c) and rhombohedral to tetragonal phase transition temperature (T_r−t) were found to be in the range of 173–212°C and 114–155°C, respectively, indicating that the T_r-t was increased with adding PIN component. In the MPB region, the highest T_r-t = 155°C was found in 0.32PIN–0.38PMN–0.30PT ceramic, that greatly expanded temperature usage range.

The dielectric integrity has been one of the major obstacle in bringing out capacitor devices with suitable performance characteristics at high temperatures. In this paper, B_xN_yO_z dielectric films for high temperature capacitors solutions are investigated. The films were grown on silicon substrate by using ion source assisted physical vapor deposition technique. The as-grown films were characterized by SEM, XRD, and XPS. The capacitor structures were fabricated using B_xN_yO_z as a dielectric and titanium as metal electrodes. The elaborated devices were subjected to electrical and thermal characterization. They exhibited low electrical loss and very good stability when subjected to high temperature for a prolonged period of time.

The temperature coefficient of permittivity ($\mathrm{\text{TC}}\epsilon$) of BaTiO₃–Bi(Me)O₃ solid solutions were investigated. It was determined that as the tolerance factor was decreased with the addition of Bi(Me)O₃, the $TC\epsilon$ shifted from large negative values to $\mathrm{\text{TC}}\epsilon$ values approaching zero. It is proposed that the different bonding nature of the dopant cation affects the magnitude and temperature stability of the permittivity. This study suggests that the relationship between tolerance factor and $\mathrm{\text{TC}}\epsilon$ can be used as a guide to design new dielectric compounds exhibiting temperature-stable high permittivity characteristics, which is similar to past research on perovskite and pyrochlore-based microwave dielectrics.

Conductor–dielectric 0–3 nanocomposites using spherical nickel nanoparticles as filler and poly(vinylidene fluoride–trifluoroethylene) 70/30mol.% as matrix are prepared using a newly developed process that combines a solution cast and a hot-pressing method with a unique configuration and creates a uniform microstructure in the composites. The uniform microstructure results in a high percolation threshold ${\phi }_c$ ($>55$ vol.%). The dielectric properties of the nanocomposites at different frequencies over a temperature range from $-$70${}^{\circ }$C to 135${}^{\circ }$C are studied. The results indicate that the composites exhibit a lower electrical conductivity than the polymer matrix. It is found that the nanocomposites can exhibit an ultra-high dielectric constant, more than 1500 with a loss of about 1.0 at 1kHz, when the Ni content (53 vol.%) is close to percolation threshold. For the nanocomposites with 50 vol.% Ni particles, a dielectric constant more than 600 with a loss less than 0.2 is achieved. It is concluded that the loss including high loss is dominated by polarization process rather than the electrical conductivity. It is also found that the appearance of Ni particles has a strong influence on the crystallization process in the polymer matrix so that the polymer is converted from a typical ferroelectric to a relaxor ferroelectric. It is also demonstrated that the widely used relationship between the dielectric constant and the composition of the composites may not be valid.

This work prepares (Ba${}_{0.5}$Sr${}_{0.5}$)TiO₃ (BST)-doped (Bi${}_{1∕2}$Na${}_{1∕2}$)TiO₃ (NBT) lead free ceramics through conventional solid reaction method and analyzes the doping effect of BST on phases, microstructure, dielectric and ferroelectric properties. The phase and structure of the NBT-BST ceramics were investigated through X-ray diffractometer (XRD) and Raman. The XRD results showed that BST has diffused into the NBT lattices to form a stable solid solution; while, Raman spectrum showed the bands at low frequency are different with that of pure NBT and divided into two ranges around 247cm${}^{-1}$ and 303cm${}^{-1}$. Relative dense and homogeneous ceramic microstructures could be achieved, with the observation of a slight decrease in average grain size with the increase of BST doping content. The dielectric and ferroelectric properties were also investigated. The dielectric constant increases gradually with increasing the temperature to $T_{\mathrm{\text{m}}}$, and then decrease. The temperature dependence property showed diffused phase transition near $T_{\mathrm{\text{m}}}$. The polarization-electric field ($P$-$E$) hysteresis loops of BST-doped NBT ceramics showed typical ferroelectric or relaxor nature. Both the $E_{\mathrm{\text{c}}}$ and $P_{\mathrm{\text{r}}}$ increased first, then decreased with respect to the increase of the BST content.

Lead-free sodium–potassium niobate-based piezoelectric materials are most intensively studied in order to replace the widely used Pb-based ones. In this work, the effects of modification of compositions by donor and acceptor dopants in the A- and B-sites of perovskite lattice on structure, dielectric, ferroelectric, and piezoelectric properties of ceramics from Morphotropic Phase Boundary in the ($1-x$)(K${}_{0.5}$Na${}_{0.5}$)NbO₃–$x$BaTiO₃ system and in compositions with $x=0.05$ and 0.06 additionally doped by Ni${}^{3+}$ cations have been studied.

In this work, we report the dielectric properties of Single wall Carbon Nanotubes (SWCNTs)-based phantom that is mainly composed of gelatin and water. The fabricated gelatin-based phantom with desired dielectric properties was fabricated and doped with different concentrations of SWCNTs (e.g., 0%, 0.05%, 0.10%, 0.15%, 0.2%, 0.4% and 0.6%). The dielectric constants (real ${\epsilon }^{\prime }$ and imaginary ${\epsilon }^{\prime \prime })$ were measured at different positions for each sample as a function of frequency (0.5–20GHz) and concentrations of SWCNTs and their averages were found. The Cole–Cole plot (${\epsilon }^{\prime }$ versus ${\epsilon }^{\prime \prime })$ was obtained for each concentration of SWCNTs and was used to obtain the static dielectric constant ${\epsilon }_s$, the dielectric constant at the high limit of frequency ${\epsilon }_{\infty }$ and the average relaxation time $\tau$. The measurements showed that the fabricated samples are in good homogeneity and the SWCNTs are dispersed well in the samples as an acceptable standard deviation is achieved. The study showed a linear increase in the static dielectric constant ${\epsilon }_s$ and invariance of the average relaxation time $\tau$ and the value of ${\epsilon }_{\infty }$ at room temperature for the investigated concentrations of SWCNTs.

Zinc substituted cobalt ferrite nanoparticles with elemental composition Co${}_{1-x}$Zn_xFe₂O₄ ($x=0.0$, 0.2, 0.4, 0.6) were prepared by the sol-gel auto-combustion technique using Co, Fe, Zn nitrate as a precursor where nitrates to citrate was 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 900^∘C for 3h. Structural, morphological, dielectric and magnetic properties were studied by x-ray diffractometer (XRD), scanning electron microscope (SEM), high precision impedance analyzer and vibrating sample magnetometer (VSM), respectively. The peaks obtained from the XRD confirmed samples having crystallite ($\sim$32–36nm) single phase inverse spinel structure without any traceable impurity. Lattice parameters were calculated from XRD and it increases with Zn content. SEM revealed irregularly shaped grains ($\sim 0.5$–0.7$\mu$m) morphology with heterogeneous distribution. The dielectric constant (${\epsilon }^{\prime }$) and dielectric loss ($tan\delta$), have been measured as a function of frequency at room temperature. The dependence of ${\epsilon }^{\prime }$ and $tan\delta$ with frequency showed the normal dielectric behavior in accordance with the Maxwell-Wagner type of interfacial polarization and electron hopping change between Co${}^{2+}$ and Co${}^{3+}$ as well as between Fe${}^{2+}$ and Fe${}^{3+}$ ions at octahedral sites.

The study aims to investigate the structural and dielectric properties of perovskite La${}_{1-x}$Sr_xFeO₃ ($x$ = 0.1, 0.2, 0.3, and 0.4) synthesized by sol–gel and sintering methods. X-ray diffraction (XRD), transmission electron microscopy (TEM), and LCR-Meter were used to identify the phase, crystallography parameters, morphology, particle size, and electrical behavior of the synthesized perovskite materials. The samples showed a single-phase orthorhombic crystal structure with Pbnm space group. Sr-substitution induced the volume unit cell and crystallite size to decrease. The synthesized nanoparticles were uniform and homogeneous with the particle size less than 200nm. Impedance spectroscopy (IS) was used to explain the electrical behavior as a function of frequency (100Hz to 1MHz) at various temperatures (300–373K). The presence of small polarons as charge carriers within the grain and grain boundary were elucidated from the electrical conductivity experiments. Sr-substitution caused the dielectric constant and electronic conductivity to increase with the highest values obtained from La${}_{1-x}$Sr_xFeO₃ ($x=0.4$).

CaO doped 0.5Na${}_{0.5}$Bi${}_{0.5}$TiO₃ (NBT)-0.5SrTiO₃ (ST) were prepared by a traditional solid-reaction method under various sintering temperatures. X-ray diffraction (XRD), electron scanning microscopy (SEM), and electrical measurements were employed to check the phases, microstructures, and energy storage properties. The doping of CaO can deeply affect the relaxation nature of NBT-ST ceramics. So the energy storage performance could be modified. Specially, sample with 1 at.% CaO exhibits a high energy storage density of 1.51J/cm³. Any further details can be found within this study.

Polycrystalline NiCuZn ferrite (Ni_xCu${}_{0.3}$Zn${}_{0.7-x}$Fe₂O₄; $x=0.2$, 0.3, 0.4 and 0.5) were prepared through sol–gel auto combustion method applying double sintering technique. Structural, morphological, elemental analyses (EDS), Fourier-transform infrared spectroscopy (FTIR), Direct Current (DC) electrical resistivity, dielectric, magnetic and optical properties of prepared samples were analyzed. XRD profiles reveal the formation of simple cubic spinel structure without any traceable impurity. The average crystallite size lies within the range of 22–29nm. Lattice parameter decreases with increasing Ni concentration. Room temperature DC resistivity was recorded from $6.39\times 10^5$ to $3.79\times 10^5$$\mathrm{\Omega }$cm. Both dielectric constant ($\dot{\epsilon }$) and loss factor (tan$\delta$) were decreased with increase of frequency while AC conductivity increases. FTIR absorption peak occurred at three different frequency ranges at 570–577cm${}^{-1}$, 1635–1662cm${}^{-1}$ and 3439–3448cm${}^{-1}$. Magnetic properties were investigated by using vibrating sample magnetometer (VSM). Decreasing trends were observed for saturation magnetization ($M_s$), magnetic coercivity ($H_c$) and remanant magnetization ($M_r$) with the increase of Ni content. Optical band gap ($\sim$2.70–2.79eV) were calculated from diffuse reflectance data by using Kubelka–Munk function.

The modification of the structure lanthanum orthoferrites (LaFeO${}_3)$ to obtain ceramic materials with enhanced structural, optical, and electrical properties constitutes an active area of research. The preparation of La${}_{0.8}$Pb${}_{0.2}$(Fe, Ti)${}_{0.5}$O₃ (LPFTO) ceramic nanoparticles by following a cation substitution approach from LaFeO₃ using sol–gel and sintering methods is described. The electrical and dielectric properties of the obtained material are investigated. The contribution of grain and grain boundary in the conduction mechanism is demonstrated by complex impedance analysis. The LPFTO ceramic nanoparticles exhibit a giant dielectric constant of the order of 10⁸. The conductivity analysis suggests the occurrence of thermally activated semiconductor behavior. Moreover, the ferromagnetic–paramagnetic semiconductor transition temperature is observed at 385K. The ac conductivity behavior satisfies the nonoverlapping small-polaron tunneling (NSPT) model.

Solid solutions of the lead-free 0.88(${\text{Na}}_{0.5}$${\text{Bi}}_{0.5})$TiO₃-0.12(${\text{Ba}}_{1-x}$${\text{Sm}}_x)$TiO₃ (NBT-BT: $x$Sm) ferroelectric ceramics were synthesized by solid state reaction. The doping of Sm promotes the structure of the ceramics to transform toward morphotropic phase boundary, and it decreases the grain size of the ceramics. With the increase of Sm content, the ferroelectric properties are improved gradually, where the ferroelectric polarization increases and the coercive field decreases. Sm doping induces a dielectric anomaly with obvious frequency dispersion at a low temperature, exhibiting the transition from the ferroelectric to relaxor state. Moreover, the photoluminescence spectra of NBT-BT:$x$Sm ceramics exhibit a strong orange emission upon blue light excitation of the 400nm to 500nm. The emission intensities are strongly dependent on the Sm doping concentration, which reached the optimal value as the doping concentration is 0.7%. These results suggest that the NBT-BT:$x$Sm ceramics may have significant technological promise in novel multifunctional devices.

SrTiO₃/ZnTiO₃ heterolayered thin films were fabricated by spin coating Sr–Ti and Zn–Ti sol–gel precursors on fused silica substrate. The SrTiO₃ and ZnTiO₃ were coated alternatively to form ABAB heterolayered thin films. The thickness of individual layers was tailored by controlling the coating layers. The structure characterization of the thin films showed independent structure of each layer while the microwave dielectric properties and optical band gaps can be tuned by changing the layer configuration. The effects of the layer configuration on the dielectric and optical properties were studied.

The perovskite (${\text{La}}_{0.7}$${\text{Ba}}_{0.3})$(${\text{Mn}}_{0.5}$${\text{Fe}}_{0.5}{){}_{1-}}_x$${\text{Zr}}_x$O₃, where $x$ = 0.1, 0.2 and 0.3, ceramics were synthesized by solid-state reaction method. The introductory structural studies were followed through by X-ray diffraction technique and the results have disclosed that all the samples were crystallized into an isolated phase. The Zr substitution in the resulting solid solutions increases the electrical conductivity and the maximum value of ac conductivity has been found to be $\sim$118.8 S ${}^{.}$ cm${}^{-1}$ for $x$ = 0.3 at 200${}^{\circ }$C (at 1 MHz). The frequency dependence of ac conductivity data follows Jonscher’s power law. The variation of the exponent $n$ versus temperature follows the nonoverlapping small polaron tunneling (NSPT) model. The dielectric relaxation has been observed to be of non-Debye nature for all measuring temperatures (50–200${}^{\circ }$C). The impedance spectroscopy reveals that all the samples exhibit negative temperature coefficient of resistance (NTCR) behavior. The prepared samples (for $x$ > 1) are supposed to be suitable for cathode materials in SOFCs.