Search

The work presents coherent manipulation of wavelength interrogation sensitivity of surface plasmon polariton waves (SPPs) with respect to refractive index dλ/dnd. Significant control in sensitivity is reported with probe and control field detunings and Rabi frequency as well as decay rates. The order of diffraction and grating period of the slide play an important role in the manipulation of wavelength interrogation of sensitivity. The sensitivity increases with increasing grating period and decreases with increasing order of diffraction. The sensitivity is oscillation function of probe field detuning and Rabi frequency. A maximum value of sensitivity is reported to 800nm/RIU with probe field detuning and Rabi frequency, while minimum value of sensitivity is investigated up to 60nm/RIU with probe field detuning and decay rates. The reported results might have benefits in biomedical and optical technologies.

The combination of low dielectric constant (er) and a high-quality factor (Q × f) in MgO ceramics makes them attractive for 5G applications. However, the large negative temperature coefficient of resonance frequency (τf) impedes these applications. In this paper, the composite ceramics of MgO–xMTiO3 (M = Ca, Sr; x = 0, 2.5, 5, 7.5, 10 wt%) with the addition of 4 mol% LiF as a sintering aid were fabricated by the traditional solid-state reaction method. The coexistence both MgO and MT phases can be observed in XRD and SEM in the 4 mol% LiF–MgO–wt%MTiO3 systems under the high-temperature sintering process. With the addition of MT, the grain size of MgO decreased, the er value improved with τf value gradually increasing from negative to positive value. Optimized microwave dielectric properties were achieved for 4 mol%LiF–MgO–10wt%SrTiO3 ceramics sintered at 1300 °C for 6 h, yielding er = 11.2, Q × f = 46, 815 GHz, and τf = + 3.51 ppm/°C. Based on it, a prototype of microstrip patch antenna was designed and fabricated with a center frequency at 5.64 GHz for 5G–Sub6GHz communication applications.

In this paper, (1-x)LiWVO6-xK2MoO4 (LWVO-KMO, x = 60, 65, 70, 75, 80, 90 wt%) composite ceramics with >92% relative density were prepared by cold sintering at 160 °C under a uniaxial pressure of 300 MPa for 1 h. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman spectroscopy demonstrate that LWVO and KMO coexist without other impurities. (1-x)LWVO-xKMO composite ceramics exhibit relative permittivity (er) ranging from 6.8 to 8.5, microwave quality factor (Q × f) ranging from 2050 to 7182 GHz, and temperature coefficient of resonant frequency (τf) ranging from −49 to +25 ppm/°C. Based on cold sintered 30 wt%LWVO-70 wt%KMO composite ceramic with er ~7.8, Q × f ~4514 GHz, and near zero τf ~1.3 ppm/°C, a prototype microstrip patch antenna was designed and manufactured. Through testing, it shows excellent antenna performance with a center frequency of 6.58 GHz, a bandwidth of 170 MHz (−10 dB) and a total efficiency of up to 89.5%.

Over the last two decades, perovskites have attracted researchers’ attention due to their fascinating physical properties for different components in the electronic industry. Here, we have investigated the electronic structure and thermoelectric properties of KPdX3 (X = F, Cl, Br, I) perovskites using Density Functional Theory (DFT). Initially, the structure of all the compounds was relaxed, and the optimized lattice parameters were obtained using the PBE functional. The phonon dispersion spectrum obtained for all compounds indicated a dynamically stable nature for these perovskites. The analysis of the electronic band structure showed metallic nature for KPdX3. The calculated elastic properties offer elastic stability and ductility for KPdX3. The appropriate values of thermoelectric parameters show the potential of these KPdX3 for thermoelectric applications. Moreover, the thermoelectric performance of these compounds can be further improved by tuning the thermal conductivity by selecting an appropriate cation as a dopant. The thermoelectric properties of KPdX3 can guide future experimental and theoretical studies.

Bismuth is considered as one of the most promising candidates to replace Pb in the organo-lead halide perovskite, a classical material for various optoelectronic applications. When utilized in a photovoltaic cell, the performance of the cell drops due to deterioration in the absorber film and the changes in its crystal structures. In this work, a small amount of dodecylammonium chloride, C12H25NH3Cl (DCl) is added into Cs3Bi2I9 (CBI), resulting in a pinhole-free high-quality perovskite (PVK) film via a single-step solution processability, also confirmed by FTIR and XPS analyses. Structural, optical, and microscopic analyses showed that the quality, surface features, and crystallinity of the CBI films are significantly improved by adding DCl. The prepared films are successfully demonstrated in a solar cell and exhibited considerably improved photovoltaic (PV) characteristics (VOC by ~47%, JSC by ~33%, FF by 13%, and PCE by 115%) over pure CBI-based devices. Moreover, the PV device retained more than 95% of its initial PCE in the ambient laboratory environment (relative humidity 55±5%). To the best of our knowledge, this is the highest PCE along with extended environmental stability reported for solution processed CBI-based perovskite solar cells.

In this study, Ca4−xLa2+xTi5−xBxO17 (B = Al, Ga; x = 0, 1) ceramics were processed via a mixed oxide solid state sintering route and characterized using XRD, SEM, EDS and Vector Network Analyzer. Phase analysis of the samples showed single phase formation for the sample x = 0 while secondary phases formed for Ca4−xLa2+xTi5−xBxO17 (B = Al, Ga; x = 1) ceramics. Ca4La2Ti5O17 exhibited ∈r = 74, Q×fo = 14,116 GHz and τf = 157 ppm/°C. The substitution of Ga or Al for Ti at the B-site of Ca4La2Ti5O17 ceramics significantly improved the microwave dielectric properties i.e. Ca3La3Ti4GaO17 and Ca3La3Ti4AlO17 have ∈r = 44, Q×fo = 16,128 GHz and τf = 7.3 ppm/°C and ∈r = 46, Q×fo = 13,754 GHz and τf = −2 ppm/°C, respectively. The microwave dielectric properties of these materials are suitable for high frequency microwave applications.

Owing to their high efficiency and extended environmental stability, hybrid 2D/3D-perovskites (HPVKs) are gaining an increasing interest in the field of organometal halide perovskite solar cells (PSCs). In HPVKs, the 3D component acts as an active material, where its 2D-counterpart provides protection against environmental factors. Here in, we add dodecylammonium-chloride (DACl) into the precursor solution of 3D-perovskites (FAMAPbI3) to achieve HPVKs. The formation of HPVK is confirmed by XRD, optical absorption, and Fourier-transform infrared (FTIR) spectroscopies. The structural and optical analysis affirmed that in the case of HPVKs, not only the crystallinity of perovskites is improved significantly but also a variation in its structural properties and optical bandgap have occurred. It is also observed that the surface morphologies of HPVK films are considerably improved with the incorporation of DACl. A minute amount of CsI is also added into the precursor solution of HPVKs, which further assist the formation of HPVKs and consequently causes a significant increase in the carrier lifetime. Finally, a solar cell made of HPVKs shows an improved PCE than pure 3D-perovskites. All HPVKs films and solar-cells are prepared in the ambient humidity and found to be more hydrophobic and stable, not only under relative humidity >50% but also under high thermal stress of 85 ℃.

Characterization and synthesis of CU 2 ZnSnS 4 thin film is the main theme of this study. CZTS thin films are fabricated on glass substrate. This sample are annealed at 300C° for one hour. Transmittance and absorbance of the thin film was calculated from optical data recorded on spectrometer. From voltage current characteristics, the resistance and resistivity of the sample were calculated.

B-site doping in potassium sodium niobate (KNN) with Mn2+ (M⁢nNb″′) and Ti4+ (T⁢iNb′) dopants were soluble but prevented KNN from achieving a high relative density, while Sn4+ (S⁢nNb′) was not soluble in the structure as evidenced by second phase peaks in X-ray diffraction (XRD) traces. However, SnO2 was an effective sintering aid in KNN-50/50. A-site doping with Sr2+ (S⁢r(Na,K)⋅) up to 1 mol% initially improved dielectric properties but higher sintering temperatures were required for compositions with >1 mol% Sr. Samples with 5% and 7% of Sr-doping completely shifted the transition of TO–T to below RT and broadened the TC peaks as the relaxor. All Ti-doped and Sr-doped compositions showed an increase in conductivity, manifested as high values of dielectric loss (tanδ). More than 1% of acceptor and donor dopants showed the ionic-type conduction mechanism, while 1% displayed the electronic mechanism as attributed from the strongly frequency-dependent tanδ. In conclusion, these samples have the potential to open up new applications in the field of electroceramics.

The remarkable optoelectronic properties and considerable performance of the organo lead‐halide perovskites (PVKs) in various optoelectronic applications grasp tremendous scientific attention. However, the existence of the toxic lead in these compounds is threatening human health and remains a major concern in the way of their commercialization. To address this issue, numerous nontoxic alternatives have been reported. Among these alternatives, bismuth‐based PVKs have emerged as a promising substitute because of similar optoelectronic properties and extended environmental stability. This work communicates briefly about the possible lead‐alternatives and explores bismuth‐based perovskites comprehensively, in terms of their structures, optoelectronic properties, and applications. A brief description of lead‐toxification is provided and the possible Pb‐alternatives from the periodic table are scrutinized. Then, the classification and crystal structures of various Bi‐based perovskites are elaborated on. Detailed optoelectronic properties of Bi‐based perovskites are also described and their optoelectronic applications are abridged. The overall photovoltaic applications along with device characteristics (i.e., V OC, J SC, fill factor, FF, and power conversion efficiency, PCE), fabrication method, device architecture, and operational stability are also summarized. Finally, a conclusion is drawn where a brief outlook highlights the challenges that hamper the future progress of Bi‐based optoelectronic devices and suggestions for future directions are provided., The toxic‐lead in organometal‐halide perovskites is hindering their applications and readily needs a replacement. This work communicates briefly about the possible nontoxic lead alternatives and explores bismuth‐based perovskites comprehensively, in terms of their structures, optoelectronic properties, and applications. This work is helpful to improve the material and performance of the bismuth‐based perovskites to bring them on par with lead‐based perovskites.

(1-x)K0.4Na0.6NbO3–xBiFeO3 lead-free piezoelectric ceramics were successfully prepared in a single perovskite phase using the conventional solid-state synthesis. Relative permittivity (εr) as a function of temperature indicated that small additions of BiFeO3 not only broadened and lowered the cubic to tetragonal phase transition (TC) but also shifted the tetragonal to orthorhombic phase transition (TO–T) toward room temperature (RT). Ceramics with x = 1 mol.% showed optimum properties with small and large signal piezoelectric coefficient, d33 = 182 pC/N and d∗33 = 250 pm/V, respectively, electromechanical coupling coefficient, kp = 50%, and TC = 355°C. kp varied by ∼5% from RT to 90°C, while d∗33 showed a variation of ∼15% from RT to 75°C, indicating that piezoelectric properties were stable with temperature in the orthorhombic phase field. However, above the onset of TO–T, the properties monotonically degraded in the tetragonal phase field as TC was approached.

The relationship between the piezoelectric properties and the structure/microstructure for 0.05Bi(Mg2/3Nb1/3)O3-(0.95-x)BaTiO3-xBiFeO3 (BBFT, x = 0.55, 0.60, 0.63, 0.65, 0.70, and 0.75) ceramics has been investigated. Scanning electron microscopy revealed a homogeneous microstructure for x < 0.75 but there was evidence of a core-shell cation distribution for x = 0.75 which could be suppressed in part through quenching from the sintering temperature. X-ray diffraction (XRD) suggested a gradual structural transition from pseudocubic to rhombohedral for 0.63

Lead-free ceramics with high recoverable energy density (Wrec) and energy storage efficiency (η) are attractive for advanced pulsed power capacitors to enable greater miniaturization and integration. In this work, dense bismuth ferrite (BF)-based, lead-free 0.75(Bi1−xNdx)FeO3-0.25BaTiO3 (BNxF-BT) ceramics and multilayers were fabricated. A transition from a mixed pseudocubic and R3c to a purely pseudocubic structure was observed as x increased with the optimum properties obtained for mixed compositions. The highest energy densities, W ∼ 4.1 J cm−3 and Wrec ∼ 1.82 J cm−3, were achieved for BN15F-BT, due to the enhanced breakdown field strength (BDS ∼ 180 kV cm−1) and large maximum polarization (Pmax ∼ 40 μC cm−2). The multilayers of this composition possessed both a high Wrec of 6.74 J cm−3 and η of 77% and were stable up to 125 °C. Nd doped BF-based ceramics with enhanced BDS and large Wrec are therefore considered promising candidates for lead-free energy storage applications.

Fluorescent semiconducting conjugated polymer nanoparticles (CPNs) are promising candidates for enhanced luminescent devices and bioimaging. The key aspect of all fluorescent materials is their high radiative yield. Combination of CPNs with metal nanoparticles (MNPs) is one of the ways to increase their fluorescent yield. Most of such combinations are introduced in the forms of sophisticated core–shells and thin films or layers. Herein, we synthesized CPNs of poly[2-methoxy,5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and silver nanoparticles (AgNPs) in aqueous solution in the form of metal–polymer nanocomplexes (MPNCs), which are not only easily achievable but also show significantly enhanced optical absorption and luminescence properties. To synthesize MPNCs, AgNPs with different molar ratios were added to a colloidal solution of CPNs. The adsorption of AgNPs on the surfaces of the CPNs was confirmed by transmission electron microscopy and UV-VIS absorption spectroscopy. Fluorescence and optical absorption spectroscopies revealed a substantial increase in the optical absorption and photoluminescence (PL) intensity of the MPNCs. It was observed that at optimum concentrations of AgNPs and CPNs in the colloidal solution of MPNCs, the PL intensity is enhanced by ∼11 fold. The increase in PL intensity is attributed to the energy transfer from AgNPs to CPNs via near-field-coupling and electric field enhancement in the nanogaps present among the adsorbed AgNPs on the surfaces of the MPNCs, which is confirmed by finite difference time domain (FDTD) simulations. Since the MPNCs as well as their ingredients were prepared in aqueous solutions, we believe that such nanocomplexes could find use not only in enhanced fluorescent devices but also in therapeutics and diagnostics.

Spinel zinc ferrite nanostructures possess incredible dielectric and magnetic properties due to the presence of oxygen vacancies, cation distribution and surface spin disorder. However, the mechanism behind the photoelectrochemical properties is seldomly investigated. Herein, we report the influence of zinc non-stoichiometry on the optical, dielectric, magnetic and photoelectrochemical properties of zinc ferrite by preparing polyvinylpyrrolidone (PVP) coated and uncoated ZnxFe2O4±δ (x = 1, 0.98 and 1.02) nanostructures synthesized via the hydrothermal method. X-ray diffraction showed the formation of a single-phase spinel structure of all the samples. FTIR spectroscopy confirmed the formation of the metal oxide with two of its fingerprint vibrational bands detected near 550 cm−1 and 400 cm−1. Moreover, a decrease in bandgap (Eg) and the saturation magnetization values were observed for Zn-deficient samples. The dielectric constant and dielectric tangent loss measurement showed similar dielectric behavior for all the ZnFe2O4 samples. The variation in dielectric permittivity and dielectric tangent loss, with the concentration of zinc, were found to be in good agreement with Koop’s phenomenological theory of dielectric dispersion. The photoelectrochemical (PEC) characterization of the prepared samples was investigated for hydrogen production under visible light irradiation. It was found that the 2% Zn-deficient electrode (higher photocurrent density, −0.336 V flat-band potential and 1575 Ohm charge transfer resistance) increased PEC water oxidation activity compared to pure and excess ZnFe2O4 electrodes. The deficiency of Zn increased the majority carrier concentration and surface defects, which in turn improved the surface charge separation efficiencies. The results give a new perspective on the importance of zinc ferrite as a catalyst to synthesize photoelectrodes for efficient solar energy conversion devices.

(1− x )BaTiO 3 - x BiMg 2/3 Ta 1/3 O 3 ( x = 0.3–0.6) ceramics were fabricated via conventional solid state sintering route. X-ray diffraction results showed single perovskite phase for x = 0.3–0.5 while secondary phase was formed for x = 0.6 sample. Raman data was consistent with XRD data indicating the formation of cubic structure. The samples exhibited flat relative permittivity over a wide temperature range. The insulation resistance was found to be 10 9 –10 12 Ω-cm and time constant 0.36–72.14 s. Impedance spectroscopy analysis of the samples indicated single Debye-like peak in the spectroscopic plot, indicative of homogeneous electrical microstructure. The temperature-stable dielectric properties suggested that this material may be useful for capacitor applications.

Ba0.5−x Ca x Bi0.5Ti0.75Mg0.25O3 (BCTM) ceramics were processed through a conventional solid state route. X-ray diffraction analysis of the compositions showed single phase cubic perovskite structure, consistent with the Raman studies. The microstructure of sintered ceramics comprised dense packed grains. Relative permittivity was observed to decrease with increase in Ca2+ concentration, presumably due to smaller ionic polarizability of Ca2+ than Ba2+. The samples exhibited high relative permittivity (1565–1980) stable over a wide range of temperature as high as 550 °C along with a high resistivity of the order 109–1010 Ω cm, suitable for high temperature applications.

A stoichiometric and 2 mol% Ba deficient samples in the formulation 0.5BaTiO3-0.5BiMg1/2Ti1/2O3 (BT-BMT) were processed via a mixed oxide solid-state route. The deficient sample exhibited a high relative permittivity (2100±15%) over the temperature range 90-450°C and a low dielectric loss (tanδ < 0.01), maintained up to high temperature (430°C). The samples exhibited intrinsic conduction mechanism and showed an n-type character. By introducing 2 mol% Ba vacancies, a dramatic influence on the dielectric loss was observed which was mainly associated with the trapping of electrons by barium-oxygen vacancy pair associated with the intentionally produced cation vacancies. Thus, control of composition by creating deficiency allows fine tuning of the dielectric properties of BT-BMT ceramics for applications in high-temperature multilayered ceramic capacitors.

In this paper, we report the characterization of NdTi0.8M0.2O3.4 (M = Ga, Al) ceramics prepared via mixed oxide solid state sintering route. X-ray diffraction analysis of the samples revealed the formation of single phase for NdTi0.8Ga0.2O3.4 sample while secondary phase was formed in the case of NdTi0.8Al0.2O3.4. Microstructural analysis of the sample showed dense packed grains. NdTi0.8M0.2O3.4 with M = Ga and Al exhibited a dielectric constant (r) = 34, quality factor (Q×f) = 9,776 and 10,867 GHz and temperature coefficient of resonance frequency (τf) = -113 and -90 ppm/oC, respectively. Further work is required on tuning the low τf of the samples for possible applications in the GHz frequency range. Keywords: Ceramics; ABO3.4, Perovskites, Microwave dielectric properties.

Studies on copper zinc tin sulpher selenide (CZTSSe) thin-film material and its applications as a base material are intensively being researched since it is an earth-abundant, inexpensive, flexible, and interesting material for next-generation optoelectronic technologies. Apropos, this study explores and reports the synthesis of CZTSSe thin films and their key optoelectronics characteristics. The reported films are fabricated on a soda-lime glass substrate by using a physical vapor deposition technique, and then annealed from 250 to 450 degrees C. From the X-ray diffraction analysis, the structure of the as-deposited thin films is found to be amorphous in nature. Annealed thin films of CZTSSe exhibit polycrystalline nature with an average crystallite size of 46.3 nm in tetragonal structure. To determine the bandgap energy, as well as optical properties, the visible spectrophotometer, and four-probe techniques, are used. From the measurements, the bandgap energy of the annealed film is found to be 1.64 eV at 450 degrees C which is in the optimal range as an absorber layer for solar cell devices. Similarly, by employing the four-probe technique, I-V characteristics for the as-deposited thin films, the material shows non-ohmic behavior whereas the annealed film demonstrates partially ohmic with a resistance of 670 ohms.

Polycrystalline (1−x)BaTiO3–0.5xBi(Mg0.5Ti0.5)O3–0.5xBiScO3 (x = 0.4, 0.45, 0.5, and 0.55) samples have been prepared via a conventional mixed-oxide solid-state sintering route. Phase analysis of the samples with x ≥ 0.45 revealed formation of single-phase cubic structure, while at x = 0.4, a minor secondary phase formed. Complex impedance spectroscopy of the samples revealed more than one type of transport mechanism (grain/bulk, grain boundary, and electrode effect). At x = 0.4, the grain boundary was less conducting than the grain; however, grains dominated the total conductivity with further increase in x. At elevated temperatures, the higher conductivity values suggest semiconducting-like behavior with negative temperature coefficient of resistivity. The composition with x = 0.55 exhibited a temperature-stable relative permittivity (er) of 1430 (±15% over 127°C to 500°C) and dielectric loss (tan δ) of

The crystal structure, microstructure and dielectric properties of layered perovskite structured La 5− x Sr x Ti 4+ x Sc 1− x O 17 ( x =0–0.8) ceramics prepared by a solid state reaction route were investigated. X-ray diffraction and Raman spectroscopy analysis revealed the formation of single phase orthorhombic ( Pnnm ) symmetry. The microwave dielectric properties ( e r , Q×f o and τ f ) of samples have been investigated as a function of composition. e r and τ f increased while Q×f o decreased with an increase in x . The sample x =0.6 exhibited e r =54.8, Q×f o = 12,260 GHz and τ f =6.7 ppm/°C which may be a suitable candidate material for dielectrically loaded antenna applications. The complex impedance spectroscopy analysis of the sample x =0.6 revealed that the sample is highly insulative with two electro-active regions (bulk and grain boundary).

Potassium sodium niobate (KNN) is a potential candidate to replace lead zirconate titanate in sensor and actuator applications but there are many fundamental science and materials processing issues to be understood before it can be used commercially, including the influence of composition and processing atmosphere on the conduction mechanisms and functional properties. Consequently, KNN pellets with different K/Na ratios were sintered to 95% relative density in air and N 2 using a conventional mixed oxide route. Oxygen vacancies (V O •• ) played a major role in the semi-conduction mechanism in low p(O 2 ) for all compositions. Impedance spectroscopy and thermo-power data confirmed KNN to be n-type in low p(O 2 ) in contradiction to previous reports of p-type behaviour. The best piezoelectric properties were observed for air- rather than N 2 -sintered samples with d 33 = 125 pC/N and k p = 0.38 obtained for K 0.51 Na 0.49 NbO 3 .

The band gap of (1 − x)KNbO3–x(Ba0.5Bi0.5)(Nb0.5Zn0.5)O3 (0 ≤ x ≤ 0.25) ceramics narrows slightly from 3.22 eV for x = 0 to 2.89 eV for x = 0.25, in broad agreement with first-principles calculations [Phys. Rev. B, 2014, 89, 235105]. In addition, an unreported piezoelectric-to-electrostrictive crossover is observed in this compositional range, which is accompanied by a continuous decrease of the maximum electric field-induced strain due to the presence of a non-ferroelectric phase. An electrostriction coefficient of 0.023 m4 C−2 is measured for x = 0.05, whilst no electromechanical response is observed for non-ferroelectric x = 0.25, even under an applied electric field of 80 kV cm−1.