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.

In this paper, the impact on the structural, optical, morphological, and electrical properties of Zn${}_{1-x}$Co_xO, $x=0.0$, 0.02 and 0.04 nanoparticles (NPs) was investigated. Zn${}_{1-x}$Co_xO, $x=0.0$, 0.02, and 0.04 were synthesized by the thermal decomposition technique. XRD confirmed Zn${}_{1-x}$Co_xO to be hexagonal wurtzite with varying x, which represented a good incorporation of dopant ions in the ZnO lattice. Field emission scanning electron microscopy (FESEM) revealed the surface morphology of prepared ZnO NPs shaped as quasi-spherical. Energy-dispersive X-ray spectroscopy (EDS) provided the compositional information of prepared NPs having concentrations of Zn, Co, and O in the prepared NPs. Fourier transform infrared (FTIR) spectra confirm the contents of the sample, their purity, and their molecular structure. The bandgap of the NPs decreases from 3.25eV to 3.14eV with an increase of x from 0.0 to 0.04. The dielectric constant decreases with x, while the AC electrical conductivity increases with applied frequency. Recently, doped ZnO NPs have been used for the preparation of dyes, which are used for the formation of highly efficient dye-sensitized solar cells (DSSC).

We calculate the second-order corrections to vacuum polarization tensor of photons at low temperatures, i.e. T ≪ 10¹⁰K(T ≪ m_e). The thermal contributions to the QED coupling constant are evaluated at temperatures below the electron mass that is T < m_e. Renormalization of QED at these temperatures has explicitly been checked. The electromagnetic properties of such a thermal medium are modified. Parameters like electric permittivity and magnetic permeability of such a medium are no more constant and become functions of temperature.

Dielectric Laser Acceleration (DLA) achieves the highest gradients among structure-based electron accelerators. The use of dielectrics increases the breakdown field limit, and thus the achievable gradient, by a factor of at least 10 in comparison to metals. Experimental demonstrations of DLA in 2013 led to the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. In ACHIP, our main goal is to build an accelerator on a silicon chip, which can accelerate electrons from below 100 keV to above 1 MeV with a gradient of at least 100 MeV/m. For stable acceleration on the chip, magnet-only focusing techniques are insufficient to compensate the strong acceleration defocusing. Thus, spatial harmonic and Alternating Phase Focusing (APF) laser-based focusing techniques have been developed. We have also developed the simplified symplectic tracking code DLAtrack6D, which makes use of the periodicity and applies only one kick per DLA cell, which is calculated by the Fourier coefficient of the synchronous spatial harmonic. Due to coupling, the Fourier coefficients of neighboring cells are not entirely independent and a field flatness optimization (similarly as in multi-cell cavities) needs to be performed. The simulation of the entire accelerator on a chip by a Particle In Cell (PIC) code is possible, but impractical for optimization purposes. Finally, we have also outlined the treatment of wake field effects in attosecond bunches in the grating within DLAtrack6D, where the wake function is computed by an external solver.

Ferroelecromagnet Pb(Fe_1/3Nb_2/3)O₃ has been synthesized and its crystal structure and dielectric, electrostrictive and magnetic properties have been investigated. The structure of PFN ceramics examined by X-ray diffraction was found perovskite-like. The dielectric constant and dielectric loss as a function of temperature at different frequencies was measured. A para-ferroelectric transition at a temperature of 403 K was found and the maximum dielectric constant at a frequency of 500 Hz at the transition temperature is as high as 9050. The piezoelectric strain at room temperature was examined. The magnetization measurements as a function of temperature in the temperature region from room temperature to 648 K with different applied magnetic fields revealed that the compound is antiferromagnetic.

We report on the dielectric permittivities in 1 kHz to 4 MHz frequency region of the ferroelectric liquid crystal (FLC) material CB500 having a TGBA phase. Molecular and collective relaxation processes have been studied in bulk and in confined environment. In the bulk sample, a Goldstone mode (GM) and a molecular mode were observed in the SmC* phase and the softmode (SM) was observed in the TGBA phase. The Goldstone mode was also present in the FLC sample confined in 0.2 μm Anopore membranes. The relaxation frequency of this mode was shifted to the higher-frequency region in comparison to that observed in the bulk sample. In the Anopore confined FLC sample, another relaxation process (AP) was observed, which possibly arises due to some collective movement of the molecules attached to the cavity walls. The relaxation frequency of this process is almost independent of temperature and this process is only observed in the SmC* phase.

The structural and dielectric properties of a PZN-PLZT solid solution were investigated. The formation of a single phase was studied by the addition of PLZT (8/60/40) in the present system. With the increase of PLZT, the content of the pyrochlore phase decreased significantly and PZN ceramics with 100% perovskite phase could be achieved with x>0.6. Dielectric properties were investigated as a function of temperature and frequency. The ferroelectric hysteresis loop shows typical characteristics of ferroelectrics.

Two batches of C₆₀ films were grown at different growth rate, using a vacuum deposition technique. X-ray diffraction patterns indicate both films have preferential (111) orientation. We measured their dielectric constant and loss factor from 80K to room temperature, and observed distinct broad and asymmetric loss peaks, attributed to orientational glass transition. The apparent activation energy was determined as 344.4 and 304.8 meV for film A and B respectively, larger than the value 280 meV in bulk C₆₀. Ngai's correlated-state model is used to simulate relaxation spectrum, and the real activation energies were calculated, which agree with the reported activation value in bulk C₆₀ very well. We propose that the structure imperfection have contributed additional dipole correlation interactions, which make the relaxation behavior of our C₆₀ films deviate from that of bulk C₆₀.

Materials with batch formula Pb_(1-x-3y/2)R_yBa_xNb₂O₆, where R=Y, (1-x)=0.73, 0.63, 0.53 and y=0.00, 0.02 have been prepared by the double sintering method. Substitution of yttrium (Y) restored tetragonal symmetry of PBN but reduced lattice parameters, cell volume and enhanced the density. Transition temperature of PBN has decreased due to the substitution of Y³⁺. Enhanced room temperature spontaneous polarization (P_s)=149.97 μC/sq. cm has been observed in PBN53, which is above MPB, whereas enhanced value of P_s=112.74 μC/sq. cm is found in Y: PBN63 at MPB region. The room temperature Pyroelectric coefficient (P_RT=1.07) has been observed in the composition where maximum volume of P_s is obtained. Similarly, enhanced values of piezoelectric coefficients K_p=0.244, K_t=0.353, K₃₁=0.131, d₃₁=60, d₃₃=159 and g₃₁=3.65 have also been found in the same material PBN53. Substitution of Yttrium enhanced the stiffness constant 13.59 in PBN 73 to 14.27 of Y: PBN73.

Dielectric structures promise to support high field, especially for short wakefield pulses produced by a high charged electron beam traveling in a dielectric tube. To push the gradient higher, we have tested two structures using recent upgraded Argonne wakefield accelerator facility that capable of producing up to 100 nC charge and bunch length of < 13ps (FWHM). Here we report on the experiment results that more than 80 nC beam passes through a 14 GHz dielectric loaded wakefield structure that produced an accelerating field of ~ 45 MV/m. The two structures consist of a cylindrical ceramic tube (cordierite) with a dielectric constant of 5, inner and outer radii of 5 mm and 7.49 mm, respectively, and with length of 102 mm and 23 mm long. We present measurements made with single electron bunches and also with two bunches separated by 1.5 ns. As a next step in these experiments, another structure, with an output coupler, has been designed and is presently being fabricated.

We have systematically studied the X-ray radiation effects on PZT thin ceramic disk provided by CTS Communications Components, Inc using the X-ray beam line in the Center for Advanced Micro-Structure and Devices (CAMD) in Baton Rouge, Louisiana. The photo energies of the X-ray range from 2000 eV to 8000 eV. The beam size is 10.0cm×1.0cm.We measure the dielectric constant in situ with different dose of the radiation in one sample and in different samples. The dielectric constants as a function of radiation dose are presented in the paper. It demonstrates the effects on the dielectric constant. Unexpectedly, we also found that X-ray radiation on the PZT disk generates charges on the surface of the samples. We measured the surface voltage due to the X-ray radiation with different radiation dose at the same temperature for these samples. This founding may have application potential for photoelectric devices. This is just a preliminary study. More thorough investigations are needed.

This paper reports a systematic study of tungsten bronze morphotropic phase boundary (MPB) system Pb_2-2X-3Y/2Ba_2xRE_yK_1-xNa_xNb₅O₁₅, where, x = 0.20, 0.25, 0.30, RE = Pr and Bi and y = 0.05 and their structure, microstructure, hysteresis, dielectric, piezoelectric, and Pyroelectric properties. Enhanced piezoelectric constants k_p, k_t, k₃₁, d₃₁, d₃₃, g₃₁, g₃₃, as 30.8%, 47.6%, 18.9%, 57 × 10^-12C/N, 159 × 10^-12C/N, 6.89 × 10^-3mV/N, 19.23 × 10^-3mV/N, and 13.88 × 10^-12m²/N respectively are observed in the composition for which y = 0, and x = 0.30, which is above MPB. Also, a change in thickness, 0.0159 μm has been developed for a thickness of the sample 1.2 mm, d₃₃ = 159 × 10^-12C/N and for an applied voltage of 100 V. The same material produces a length extension, 0.0475 μm for d₃₁ = 57 × 10^-12C/N, l = 10 mm, t = 1.2 mm, for an applied voltage of 100 V. Thus the material may be useful for a piezoelectric transducer. Enhanced piezoelectric coefficients, d₃₁ = 96 × 10^-12C/N and g₃₃ = 12.95 × 10^-3mV/N are also observed in the composition for which RE = Pr and x = 0.25.

Pr-doped Pb(Zr_0.65Ti_0.35)O₃ (Pb_1-xPr_x(Zr_0.65Ti_0.35)_1-x/4O₃, PPZT) ceramic samples are prepared using conventional solid-state sintering method, and their structural, dielectric, ferroelectric, and piezoelectric properties are investigated, focusing on the effects of Pr-doping. Upon increasing Pr doping level x, a transition of the crystallographic structure from rhombohedral symmetry to tetrahedral and finally to pseudocubic symmetry is observed at x ~ 0.08. The detailed dielectric measurements present a clear indication of relaxor-like behaviors at x = 0.08, while the samples at x < 0.08 offer slightly improved ferroelectric properties compared with pure Pb( Zr_0.65Ti_0.35)O₃. In spite of the dielectric relaxor behaviors induced by Pr-doping, both the ferroelectric and piezoelectric properties of PPZT are degraded at x = 0.08. The physics underlying the Pr-doping induced relaxor behaviors is then discussed.

Perovskite structured ferroelectric (Na_1/2 Bi_1/2)_0.945Ba_0.055TiO₃ (BNBT-5.5) material has been synthesized by the conventional sintering technique. X-ray analysis on the material showed a single phase compound with rhombohedral structure with lattice parameters a = 3.89 Åand α = 89.893 Å. Frequency and temperature dependence of dielectric permittivity, impedance, modulus and conductivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595^°C, respectively. The observed low frequency dielectric dispersion (LFDD) in the material could be explained by Jonschers power law and evaluated activation energies at different temperature regions. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.

In this paper, we study the preparation of titanate/polypyrrole core-shell rod-like composite particles. The mere titanate rod-like particles were prepared as core material and PPy was polymerized on their surface in different amounts. Rheological measurements showed that under an applied external electric field, shear stress of these materials significantly increased with amount of PPy in the shell layer. The yield stresses obtained from the Cho-Choi-Jhon model were correlated with dielectric properties of suspensions. Polarizability as a measure of particle polarization obtained from Havriliak–Negami model of dielectric spectra increases with the content of PPy in the samples. Furthermore, role of particle concentration and silicone oil viscosity was also investigated.

Detailed first-principle calculations of properties in zinc blende quaternary alloy ${\mathrm{\text{B}}}_x{\mathrm{\text{Al}}}_y{\mathrm{\text{In}}}_{1-x-y}\mathrm{\text{N}}$ at various concentrations are investigated using density functional theory (DFT) within virtual crystal approximation (VCA) implemented in alchemical mixing approximation. The calculated bandgaps show direct transitions at $\mathrm{\Gamma }$–$\mathrm{\Gamma }$ and indirect transitions at $\mathrm{\Gamma }$–$X$, which are opened by increasing boron concentration. The density of state (DOS) revealed upper valence band (VB1) domination by $p$-states atoms, while $s$-states dominate the lower valence band (VB2); also, the DOS shows the contribution of $d$-states to the conduction band. The first critical point in the dielectric constant ranges between 0.07–4.47 eV and is due to the first threshold optical transitions in the energy bandgap. Calculated static dielectric function (DF) ${𝜖}_1(0)$ is between 5.15 and 10.35, an indication that small energy bandgaps yield large static DFs. The present results indicate $\mathrm{\text{ZB}}$-${\mathrm{\text{B}}}_x{\mathrm{\text{Al}}}_y{\mathrm{\text{In}}}_{1-x-y}\mathrm{\text{N}}$ alloys are suitable candidates of deep ultraviolet light emitting diodes (LEDs), laser diodes (LDs) and modern solar cell since the concentrations $x$ and $y$ make the bandgap and lattice constant of $\mathrm{\text{ZB}}$-${\mathrm{\text{B}}}_x{\mathrm{\text{Al}}}_y{\mathrm{\text{In}}}_{1-x-y}\mathrm{\text{N}}$ quaternary alloys tunable to desirable values.

Electrical properties of a series of nanocrystalline aluminium-substituted cobalt ferrite CoAl${}_x$Fe${}_{2-x}$O₄ (CAFO) with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 have been explored. The electrical parameters have been measured by employing impedance and techniques. The impedance has measured as a function of frequency and temperature for all the samples. The impedance increases with the increase in Al concentration in CAFO. Cobalt ferrite is yet to be verified as a ferroelectric material. However, the electrical properties reported here are similar to conventional ferroelectric materials. Multiple (two) electrical phase transitions have been observed, the two transition temperatures are identified as T${}_D$ and T${}_M$ i.e., one is dipole relaxation transition (T${}_D$) and other one is electrical phase transition temperature. Both AC and DC measurements indicate the transition temperatures.

The multiferroic magnetoelectric materials have gained intensive research interest in the recent years due to their prospective applications. In this perspective, the thermally tunable complex impedance, dielectric behavior and room-temperature magnetoelectric coupling of xCo${}_{0.5}$Ni${}_{0.5}$Fe₂O₄–(1 - x)PbZr${}_{0.58}$Ti${}_{0.42}$O₃ (x = 0.2, 0.3 and 0.5) nanocomposites have been investigated. A series of samples have been prepared by chemical pyrophoric reaction process. The structural characterization confirms the coexistence of two different types of phases, there is no phase segregation. The temperature-controlled complex impedance analysis reveals that grain boundaries and grain of the nanocomposites are playing a dominating role. The existence of Maxwell–Wagner interfacial polarization of the nanocomposites causes a high dielectric constant at low frequency. The calculated AC conductivity values with frequency at different temperatures follow the Jonscher’s power-law. A small polaronic hopping contributes largely to the conduction process of the decorated composite. The magnetostriction properties lead to the AC and DC magnetic field-dependent magnetoelectric coupling of the nanocomposites. The magnetoelectric coupling coefficient depends on the concentration of the piezomagnetic phase of the composites.

For the first of its kind, Cr${}^{3+}$-substituted calcium hexaferrite (CaCr_xFe${}_{12-x}$O${}_{19}$ ($x=1$, 3, 5 and 7)) nanoparticles (NPs) were synthesized via a facile, economical, eco-friendly lemon juice extract mediated green solution combustion method. The samples were calcined followed by characterization. The Bragg reflections confirm the formation of a single phase M-type hexaferrite crystal structure. No other impurity or mixed phases are observed even after the substitution of Cr${}^{3+}$ to the host matrix. Meanwhile, the crystallite size decreases from 29.44 to 19.92nm with an increase in the substitution of Cr${}^{3+}$ ions. The surface morphological analysis shows the presence of agglomerated irregularly shaped NPs. The direct energy band gap estimated using Wood and Tauc’s relation depicts the decrease in energy band gap from 2.98 to 2.74eV with an increase in the substitution of Cr${}^{3+}$ ions. These Cr${}^{3+}$-substituted calcium hexaferrite NPs were predicted to be useful in high-frequency applications based on structural, dielectric, and magnetic studies.

Calcium ferrite nanoparticles (NPs), doped with Zinc in the range of 10–50mol%, were synthesized through a solution combustion method using citrus Limon extract as a reducing agent, followed by calcination at 500^∘C. The synthesized samples are characterized with different techniques. Bragg reflections confirmed the formation of orthorhombic crystal structure. The shifting of the peak toward higher angle side is observed with increase in the dopant concentration. The surface exhibited irregular shapes and sized NPs with pores and voids in their morphology. The direct energy band gap increases from 2.91 to 2.97eV with increase in Zinc concentration. Further, magnetic and dielectric properties were carried out to know their importance in the high-frequency devices. Magnetic parameters, such as saturation magnetization (M_s), remanence (M_r), and coercivity (H_c) values, are discussed. M_s, M_r and H_c increase with increase in dopant concentration upto 30mol% and thereafter decreases. The dielectric studies revealed a decreasing dielectric constant from 2.98 to 1.84 as the dopant concentration increased. These findings suggest the potential use of these samples in memory devices and high-frequency applications.