- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Photoluminescence and ferroelectric behaviors related to Sr/Ba ratio in Eu3+ doped (Sr Ba1-)0.98Eu0.02Nb2O6 multifunctional tungsten bronze ceramics
摘要： The lead-free Eu3+ doped (SrxBa1-x)0.98Eu0.02Nb2O6 (SBEN, 0.3 (cid:2) x (cid:2) 07) ceramics were fabricated by conventional solid-state reaction method. Eu3+ was chosen as a dopant with the goal of inducing strong red-emitting photoluminescence based on their electrical properties. Effects of Sr/Ba ratio on the crystal structure, dielectric, ferroelectric and photoluminescent properties of SBEN ceramics were investigated by changing x. Single tungsten bronze structure with P4bm space group was obtained for all ceramics. The ceramics grain morphology varied obviously from homogenous equiaxed shape to anisometric pillar-type shape with increasing x. According to the dielectric spectra, the obtained SBEN ceramics transited from normal ferroelectrics to relaxor ferroelectrics, accompanied by the gradual decrease of Tm with increasing Sr2+ amount in A-sites. Two strong emitting peaks corresponding to the orange magnetic dipole transitions (594 nm, 5D0/7F1) and red electric dipole transitions (618 nm, 5D0/7F2) were obtained for all SBEN ceramics. The red/orange-emitting ratio of Eu3+ related to the Sr/Ba ratio in the composition was studied in this work to discuss the ions occupying situation in different A-sites.
关键词： Relaxor ferroelectrics,Dielectric properties,Luminescence,Tungsten bronze structure
更新于2025-09-10 09:29:36
-
Effect of Co Doping on Microstructures and Dielectric Properties of ZnO
摘要： Pure and Co-doped ZnO nanoparticles ( 2.5, 5, 7.5 and 10 at% Co) are synthesized by sol-gel method. The as-synthesized nanoparticles are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscopy (FE-SEM) analysis. The nanoparticles of 0, 2.5, 5at% Co doped ZnO exhibited hexagonal wurtzite structure and have no other phases. Moreover, The (101) diffraction peaks position of Co-doped ZnO shift toward smaller value of diffraction angle compared with pure ZnO powders. The results confirm that Co ions were well incorporated into ZnO crystal lattice. Simultaneously, Co doping also inhibited the growth of particles and the crystallite size decreased from 43.11 nm to 36.63 nm with the increase in doping concentration from 0 to 10at%. The values of the optical band gap Eg of all Co-doped ZnO nanoparticles gradually decreased from 3.09eV to 2.66eV with Co content increasing. Particular, the dielectric constant of all Co-doped ZnO ceramics gradually increased from 1.62×103 to 20.52×103, and the dielectric loss decreased from 2.36 to 1.28 when Co content increased from 0 to 10at%.
关键词： ZnO,Ceramics,Nanoparticles,Dielectric properties,Co-doping
更新于2025-09-10 09:29:36
-
Characterization of CuInSTe/CdS Heterojunctions
摘要： In this work, the role of substrate temperature in the range (293-423)K on the structure and microstructure of CuInSTe thin films was investigated. The results showed that the structure was amorphous for films prepared at ambient temperature Ts=293Kwhile it was polycrystalline for films prepared at high temperature. The grain size and roughness increased with increasing substrate temperature. The frequency and temperature dependencies upon AC conductivity were investigated in the frequency range 100Hz-10MHz and temperature of heat treatment in the range of 303-453K. The AC activation energy was found to increase from 0.1132 to 0.1258 eV with increasing substrate temperature from 293 to 423K and decrease to 0.0962 eV with increasing frequency from 100 to 107 Hz. The exponents show a nonsystematic sequence with the increment of substrate temperature. The obtained results gave indication t hat there is a relation between the structure and preparation temperature as well as heat treatment. According to the current-voltage characteristic, the CuInSTe/CdS heterojunction prepared at substrate temperature of 423K showed the best electrical characteristics under illumination conditions.
关键词： Activation energy,Heterojunction,quaternary alloy CuInSTe,dielectric properties,Thin films
更新于2025-09-10 09:29:36
-
Structural and electrical properties of Gd-doped BiFeO3:BaTiO3 (3:2) multiferroic ceramic materials
摘要： Gadolinium doped BiFeO3:BaTiO3 (3:2) polycrystalline multiferroic ceramics have been prepared by high-temperature solid state reaction technique. X-ray diffraction (XRD) analysis at room temperature of the prepared materials confirmed the formation of the compounds with rhombohedral crystal structure. The average particle size of as prepared samples have been found in the range of 35 nm to 55 nm for different doping concentrations. The average grain size of as prepared samples are less than 100 nm which is confirmed from SEM study. The SEM of annealed compounds showed the uniform distribution of grains and the formation of dense ceramic with average grain size in the order of 4 μm. Dielectric studies of the materials reveals that the dielectric constant ( εr ) and tangent loss (tan δ) decreases with doping concentrations at room temperature. The variation of εr and tan δ with temperature was explained on the basis of Maxwell–Wagner mechanism. The values of grain resistance ( Rb ) and grain capacitance (Cb) were obtained from Nyquist plots for the different doping concentrations at 300 °C. The activation energy ( Ea ) was calculated from the curve of frequency dependent ac conductivity ( σac ) within the range 0.19 eV to 0.45 eV. The remnant polarization of the samples (0.53 μC/cm2) was measured from polarization versus electric field (P–E) hysteresis curves. The ferromagnetic behaviour of the Gd-doped BiFeO3:BaTiO3 (3:2) sample has been studied by SQUID for the lowest doping concentration. The value of remnant magnetization was found 0.0235 emu/g at room temperature.
关键词： multiferroic ceramics,dielectric properties,ferroelectric properties,Gd-doped BiFeO3:BaTiO3,ferromagnetic properties
更新于2025-09-09 09:28:46
-
Influence of Al/Si atomic ratio on optical and electrical properties of magnetron sputtered Al1-xSixOy coatings
摘要： This work presents a study on the influence of the Al/Si atomic ratio in dc magnetron sputtered Al1-xSixOy amorphous and transparent films upon their chemical composition, films’ structure, optical and electrical properties. Increasing silicon in Al1-xSixOy films, from 0 at. % up to 31.1 at. %, caused an increment of deposition rate and an increment in Al-O-Si energy bonds as confirmed by X-Ray Photoelectron Spectroscopy (XPS) analysis. On other hand, the optical constants (refractive index (n) and extinction coefficient (k)), dielectric constant, loss tangent (tan δ) and ac conductivity (σac) decrease when the amount of silicon in films increased. The results show that the refractive index shows small variations from linearity with vol% of Al2O3 (or SiO2). Dielectric constant and dielectric loss evidenced two dipolar contributions, attributed to defects located one at or near the substrate/oxide interface, and the other in the bulk of the oxide.
关键词： Electrical conductivity,Sputtering,Dielectric properties,Aluminum silicon oxide,Optical properties
更新于2025-09-09 09:28:46
-
The influence of external stress/strain on the phase transitions and dielectric properties of potassium niobate crystal
摘要： We investigated the effects of one-dimensional shock wave compression on the structural, dielectric, and ferroelectric properties of a potassium niobate ferroelectric crystal using Landau–Ginsburg–Devonshire phenomenological theory. Our results show that the cubic to tetragonal and tetragonal to orthorhombic phase transition temperatures increase with increasing shock compression and the derivative of the phase transition temperatures with respect to stain induced by shock compression was estimated to be 21.9 °C/10?3. Additionally, the orthorhombic to rhombohedral phase transition temperature decreased with increasing shock compression and the derivative of the phase transition temperatures with respect to stain induced by shock compression was estimated to be ?144.3 °C/10?3. This result represents a 15.3% increase in the remnant polarization of the tetragonal KNbO3 crystal when the stain induced by shock compression increased from 0 to 4×10?3 at 400 °C. The dielectric susceptibilities ε33 and ε22 were calculated to decrease by approximately 20% and 40%, respectively, when the stain induced by shock compression increased from 0 to 1.6×10?3 at 350 °C. The increase in the remnant polarization and the decrease in the dielectric properties induced by shock compression provide an effective way to improve the power output capacity of a ferroelectric-pulsed power supply.
关键词： phase transition,lead-free ferroelectric crystal,ferroelectric properties,dielectric properties,shock compression
更新于2025-09-09 09:28:46
-
Structural, Infrared, Magnetic, and Electrical Properties of Ni0.6Cd0.2Cu0.2Fe2O4 Ferrites Synthesized Using Sol-Gel Method Under Different Sintering Temperatures
摘要： Ni0.6Cd0.2Cu0.2Fe2O4 ferrites were synthesized using sol-gel method under different sintering temperatures. XRD patterns with the Rietveld refinement indicate that samples crystallize in the cubic spinel structure. The increase of sintering temperature leads successively to the increase of lattice constant, average crystallite size, intensities of absorption bands, magnetization, and electrical conductivity of the prepared ferrites. Dielectric constants decrease with frequency and their behaviors have been investigated using the interfacial polarization theory predicted by Maxwell. The modulus analysis shows the presence of electrical relaxation phenomenon and non-Debye nature for the samples. An appropriate electrical equivalent circuit was used to analyze the Nyquist plots, and the results show that the conduction mechanism of the synthesized ferrites is mainly due to the grain boundary contribution.
关键词： Ferrites,conductivity,Rietveld refinement,Sol-gel method,Infrared properties,Dielectric properties
更新于2025-09-09 09:28:46
-
Microstructural, optical, and electrical characteristics of Ni/C doped BST thin films
摘要： In the present work the effect of simultaneous doping of carbon and nickel on the microstructural, optical, and electrical properties of barium strontium titanate (BST) is investigated. Thin films of BST were prepared by the sol-gel method in six different compositions ((Ba0.6Sr0.4)(NixCyTi1-x-y)O3): x = y = 0.00 (BST), x = 0.04 y = 0.00 (BST4N), x = 0.04 y = 0.01 (BST4N-1C), x = 0.04 y = 0.02 (BST4N-2C), x = 0.04 y = 0.03 (BST4N-3C), and x = y = 0.04 (BST4N-4C). Structural features and chemical bonds of the films were studied by TGA/DSC, XRD, FT-IR, and FE-SEM. The electrical and optical properties of the films were analysed by impedance spectroscopy and UV–VIS spectroscopy. The results show that addition of Ni and C leads to Ti4+-Ni2+ and Ti4+-C4+ replacements, respectively. These replacements lead to a gradual increase in the band gap energy; from 3.15 eV for BST to 3.44, 3.5, 3.66, 3.73 and 3.76 eV for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. In contrast, the dielectric loss decreases significantly from 0.055 for BST to 0.031, 0.033, 0.03, 0.022 and 0.01 for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. At the same time, the quality factor Qf (1/ tanδ) increases substantially from 15 for BST to 32, 30, 33, 44 and 87 for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. In contrast, the frequency dependence of the capacity decreases in comparison to un-doped BST. Among all films, the BST4N-4C had the highest figure of merit (FOM), least dielectric loss, and very low frequency-dependence, making it the best candidate for tuneable device applications.
关键词： Ion doping,Sol-gel,Thin-film,BaSrTiO3,Dielectric properties,Optical properties
更新于2025-09-09 09:28:46
-
Enhanced dielectric properties of BaTiO3 ceramics with cerium doping, manganese doping and Ce-Mn co-doping
摘要： Ba1?xCexTi1?yMnyO3 (where x and y varies from 0.00 to 0.03) ceramic samples are synthesized by conventional solid state reaction technique. The samples are sintered at 1473 K for 4 h. The grain size is observed to increase with increasing dopant and co-dopant concentration. The X-ray diffraction confirmed the cubic phase of these BaTiO3-based ceramics with a small amount of secondary phase. The current density shows a nearly linear relationship with voltage, and the AC resistivity of the samples is observed to decrease with increasing frequency and doping concentration. The dielectric constant and dielectric loss were observed to decrease with frequency in the lower frequency range (0.2–10 kHz), but remained almost the same at the high-frequency region (>10 kHz). Though Ce-doped samples shows better dielectric properties than Mn-doped samples, the Ce-Mn co-doped samples, having improved their dielectric properties, can be used to fabricate different optoelectric devices.
关键词： resistivity,SEM,solid state reaction,dielectric properties,XRD,grain size
更新于2025-09-09 09:28:46
-
A Novel Study: The Effect of Graphene Oxide on the Morphology, Crystal Structure, Optical and Electrical Properties of Lanthanum Ferrite Based Nano Electroceramics Synthesized by Hydrothermal Method
摘要： Lanthanum Ferrite based nanocomposites were prepared with various Graphene oxide contents by the hydrothermal method. The crystalline structure, morphological properties, electrical and optical properties of samples were investigated. X-ray diffraction results indicate that all the nano electroceramics are polycrystalline with an Orthorhombic structure. Results from scanning and transmission electron microscopes indicate that the Bismuth ferrite/Graphene oxide powders have nanostructure. The optical band gaps of the nano electroceramics were calculated for the various amount of Graphene oxide. The electrical properties of samples were investigated with the temperature depend on conductivity measurements. The measurement shows that the electrical conductivity changes with increasing temperature and graphene oxide dopants of all samples. Activation energy values of the nanocomposites decrease with increasing graphene oxide content. The dielectric properties of Lanthanum Ferrite/Graphene Oxide nanocomposites (real and imaginer) with respect to frequency variation (1 KHz–5 MHz) were measured at room temperature. The relative permittivity, dielectric loss and alternating current conductivity values of the samples were estimated. It is show that relative permittivity, dielectric loss and alternating current conductivity increase with increasing frequency. The polarization-electric field hysteresis loop of all Lanthanum Ferrite/Graphene Oxide nano electroceramics was measured at the room temperature. The loop shows proper saturation with enhanced saturation polarization and coercive electric field. The obtained findings suggest that the physical and electrical properties of Lanthanum Ferrite/Graphene Oxide nano electroceramics can be changed by Graphene Oxide doping. These materials can be used for a variety of technological applications in the field of dielectric and ferroelectric.
关键词： Dielectric Properties,Graphene Oxide,Lanthanum Ferrite,Ferroelectric,Hydrothermal Method
更新于2025-09-09 09:28:46