Structural,dielectric and reflection analysis of ZnxMg1−xTiO3 ceramics synthesized using auto-ignition combustion method

Zinc-substituted magnesium titanate Zn_xMg_1?xTiO₃ (x?=?0.00–0.10, δx?=?0.025) solid solutions were synthesized using auto-ignition combustion process and characterized for structural, dielectric and reflection properties. X-ray diffraction analysis discovered the creation of single-phase MgTiO₃. Scanning electron microscopy (SEM) indicated the existence of low porosity closely packed grains. The study of the dielectric properties indicated that for Zn_xMg_1?xTiO₃ with x?=?0.05, a reasonably great combination of the relative permittivity (?_r) with value 16.60, loss tangent (tanδ) of 0.9?×?10^?3 and temperature coefficient of resonant frequency (τ_f) of ? 41.37 ppm/°C at 10 kHz was observed. The electromagnetic reflection analysis at microwave frequencies (12.4–26.5 GHz) revealed that composition x?=?0.05 shows maximum 90% reflection bandwidth of 5.60 GHz in the Ku frequency band and 4.59 GHz in the K frequency band. These materials with low to intermediate relative permittivity, low losses, and a minor negative temperature coefficient of resonant frequency might be utilized as a resonator, antenna, and filter substrate for next-generation communication devices.

     

Structure evolutions with enhanced dielectric permittivity and ferroelectric properties of Ba(1−x)(La,Li)xTiO3 ceramics

Journal of Materials Science: Materials in Electronics - Polycrystalline Ba(1?x)(La0.50Li0.50)xTiO3 (0?≤?x?≤?0.12) ceramics are fabricated via the...     

Microstructure and dielectric properties of BaZr x Ti1−x O3 ceramics

The crystalline structure and dielectric properties of BaZr _x Ti_1−x O₃ ceramics with x = 0.05, 0.10, 0.15, and 0.20 were investigated. As zirconium increased, the a-axis lattice constant gradually increased, however, the c-axis lattice constant and c/a ratio gradually decreased. When x = 0.20, the crystal structures of the BZT ceramics are very close to cubic, different from the tetragonal structure when x < 0.20. The temperature dependence of the dielectric constant was studied and an enhanced diffuse phase transition behavior is found to be caused by the increased Zr content. The decreases of coercive electric field and remanent polarization were the result of increase of Zr/Ti ratio in BaZr _x Ti_1−x O₃.     

Effect of Si/Mg mole ratio on the phase transformation,sintering, and dielectric properties of 0.63SrTiO3–0.37LaAlO3 ceramics

Journal of Materials Science: Materials in Electronics - High-Q and temperature-stable 0.63SrTiO3–0.37LaAlO3 (63ST–37LA) ceramic with different mole ratio of Na2SiO3·9H2O/MgO...     

Structural, ferroelectric and piezoelectric properties of Mn-modified BiFeO3–BaTiO3 high-temperature ceramics

Mn modified BiFeO₃–BaTiO₃ (abbreviated as BFBT-Mnx%, x = 0.1, 0.3, 0.6, 0.9, 1.2) high-temperature lead-free ceramics were prepared by conventional oxide-mixed method and the effect of Mn doping on microstructure and electrical properties was investigated. The solid solutions show a single phase perovskite structure, and the content of Mn has a significant effect on the microstructure of ceramics. The addition of Mn can induce combinatory “hard” and “soft” piezoelectric characteristics due to aliovalent substitutions. In particular, x = 0.6 BFBT-Mnx% ceramic, with a Curie temperature, T _c, of ~463 °C, shows optimum piezoelectric properties of d ₃₃ = 131pC/N, k _p = 0.298. The simultaneous existence of good piezoelectric properties and high T _c makes these ceramics suitable for elevated temperature piezoelectric devices.     

Microwave dielectric properties of BaCu2−xMnxSi2O7 (x = 0–0.04) ceramics

Journal of Materials Science: Materials in Electronics - BaCu2?xMnxSi2O7 (x?=?0–0.04) microwave dielectric ceramics were synthesized through solid-state reaction method....     

Preparation,structure and dielectric properties of the system Sr1−xLaxTi1−xNixO3

Attempts have been made to synthesize the solid solution Sr_1–x La _x Ti_1–x Ni _x O₃ for x0.50 and its electrical behaviour has been studied. It was found that a solid solution forms for compositions up to x=0.10. The structure remained cubic. These compositions exhibited dielectric relaxator behaviour. The average grain size in these materials was very small.     

Preparation and characterization of the microstructure,dielectric and magnetoelectric properties of multiferroic Sr3CuNb2O9–CoFe2O4 ceramics

Different research methods were used to study the microstructural and magnetoelectric properties of multiferroic Sr₃CuNb₂O₉–CoFe₂O₄ (SCNO–CFO). X-ray verification provides fundamental information about the local symmetry of the two-phase SCNO–CFO ceramic. P4mm unit cell with minimal tetragonality and a cubic Fd-3m structure have been found for SCNO and CFO, respectively. Some additional traces of cupric oxide were also detected. SEM observations confirmed that the microstructure is built of various crystallites forming a two-component electroceramics and CuO-rich grain boundary segregation. Impedance spectroscopy studies reveal the thermally activated dielectric relaxations. The temperature-dependent behavior of the diffuse dielectric anomalies was successfully described by the modified Debye equation. Finally, magnetoelectric measurements clearly confirm intrinsic coupling between the piezoelectric and magnetic phases of SCNO–CFO.     

Microstructure and dielectric properties of BF–PFN ceramics with negative dielectric loss

Multiferroics with negative value of dielectric constant are very promising materials because of their modern applicability. These materials can be used as materials for the construction of electromagnetic radiation shields. The subject of the research is multiferroic BiFeO₃–PbFe_1/2Nb_1/2O₃ (BF–PFN) ceramics. For all multiferroic materials the following studies are conducted: SEM, EDS and the temperature dependence of dielectric constant ε′(T). Above a certain temperature (different for different chemical compositions) the value of dielectric constant reaches negative values. Such the behavior of the dielectric constant may indicate that the polarization inside the material has a reverse direction to the external electric field. That is, the electric field inside the material counteracts the applied external electric field. The obtaining materials also show negative dielectric losses. The Axelrod model is used to explain the mechanism that causes negative dielectric loss.     

Dielectric and electrical energy storage properties of BiFeO3–BaTiO3–SrTiO3 ternary bulk ceramics

Journal of Materials Science: Materials in Electronics - Recently, it is shown that the thin films of BiFeO3–BaTiO3–SrTiO3 have ultrahigh-energy storage density. However, the energy...     

Structure and dielectric properties of Nd x Sr1−x TiO3 ceramics for energy storage application

Polycrystalline Nd-doped SrTiO₃ ceramics with the formula Nd _x Sr_1?x TiO₃ (NSTO, x = 0, 0.024, 0.056, 0.104, 0.152, 0.200) were prepared by solid state reaction route. X-ray diffraction (XRD) analysis confirmed the formation of monophasic compounds and indicated the structure to be changed from cubic to tetragonal by increasing Nd doping concentrations. A remarkable decrease in grain size from ~30 μm for un-doped SrTiO₃ ceramics to ~1 μm for Nd-doped SrTiO₃ ceramics with x = 0.024 was observed by scanning electron microscopy. The grain size had a degree of increasing with further increasing Nd doping concentration and reached ~3 μm when the x value was 0.200. The dielectric properties of NSTO ceramics were measured at 1 kHz in ambient temperature. It revealed that the dielectric constant dramatically increases for the reason of Nd doping, leading to a maximum value of 19,800 for as-sintered sample with x = 0.104. The breakdown strength of all Nd-doped SrTiO₃ samples was found to be higher than 10 kV/mm. The relationship between dielectric properties and the microstructure feature, as well as the defect structures correlated with the charge compensation induced by trivalent Nd³⁺ doping, was discussed tentatively.     

Crystalline structure and dielectric properties of (Sr1−1.5x Bi x ) TiO3 ceramics

The crystalline structure, microstructure and dielectric properties of the (Sr_1–1.5x Bi _x )TiO₃ (0 x 0.267) ceramics were studied. Cubic solid solutions were determined for x 0.2 at room temperature. However, lattice distortion was detected by Raman spectra. A dense microstructure with the grain sizes of 2–4 m was obtained for (Sr_1–1.5x Bi _x )TiO₃ (0 x 0.2) ceramics. The Bi concentration was examined and found to be in agreement with the nominal composition and overall uniformly distributed in the sample. Different from the observations in the earlier literature for other doped quantum paraelectrics, where only an induced dielectric anomaly was reported, there are three Bi induced dielectric modes A, B, and C in the Bi doped SrTiO₃ samples. The occurrence of the impurity modes and the ferroelectric relaxor mode and their evolution are demonstrated as a function of Bi concentration.     

Structural, transport, magnetic, and dielectric properties of La1−x Te x MnO3 (x = 0.10 and 0.15)

In this study, we have investigated the structure, temperature-dependent resistivity, magnetization, and dielectric properties of La_1?x Te _x MnO_3±δ (x = 0.10 and 0.15). X-ray diffraction analysis confirms the rhombohedral crystal symmetry with space group R $ \overline{3} $ c. For both the samples, the temperature dependence of magnetization plots show paramagnetic-to-ferromagnetic phase transition. The Curie temperature (T _c) and magnitude of magnetization increase with the Te concentration. Field-dependent magnetization produces the asymmetric hysteresis loop that has been attributed to the magneto crystalline anisotropy induced by lattice distortion and the rare earth spin coupling at room temperature. Temperature-dependent resistivity plots exhibit metal–insulator transition (MIT) and charge-ordering state. These plots have been fitted using variable range hopping model, and the density of states [N(E_F)] has been estimated. Magnetoresistance is measured as a function of temperature in the field of 1T, 5T, and 8T. The dielectric constant shows an anomaly near MIT. The dielectric constant exhibits a peaking behavior with the applied frequency and the temperature dependence of dielectric constant attains colossal values at high temperatures.