Effect of Sb5+ substitution on the dielectric properties of Ag(Nb0.8Ta0.2)O3 ceramics

Sb₂O₅ were selected to substitute (Nb_0.8Ta_0.2)₂O₅ and the effects of substitution on the dielectric properties of Ag(Nb_0.8Ta_0.2)O₃ ceramics were studied. The dielectric properties of Ag(Nb_0.8Ta_0.2)_1−xSb_xO₃ ceramics were found to be improved by the substitution of Sb for Nb/Ta. The ε value of Ag(Nb_0.8Ta_0.2)_1−xSb_xO₃ ceramics sintered at 1060 °C increased from 430 to 825 with x increasing from 0 to 0.08, the tanδ value decreased sharply from 0.0085 to 0.0023 (at 1 MHz) with x increasing from 0 to 0.04, and then kept to a lower tanδ value ∼ 0.0024 with x to 0.08. The TCC values decreased from + 1450 ppm/°C for x = 0 to − 38.5 ppm/°C for x = 0.08. The Ag(Nb_0.8Ta_0.2)_1−xSb_xO₃ ceramics with x = 0.08 sintered at 1050 °C exhibited the optimum dielectric properties of ε ∼ 854, tanδ ∼ 0.0024 (1 MHz), and TCC ∼ 36.86 ppm/°C.     

Microwave dielectric properties of (Ca0.8Sr0.2)(SnxTi1−x)O3 ceramics

In this paper, we study the behavior of the B-site behavior with the incorporation of Sn⁴⁺ ion in (Ca_0.8Sr_0.2)TiO₃ ceramics. An excess of Sn⁴⁺ resulted in the formation of a secondary phase of CaSnO₃ and SrSnO₃ affecting the microwave dielectric properties of the (Ca_0.8Sr_0.2)(Sn_xTi_1?x)O₃ ceramics. The dielectric properties of the (Ca_0.8Sr_0.2)(Sn_xTi_1?x)O₃ ceramics were improved because of the solid solution of Sn⁴⁺ substitution in the B-site. The temperature coefficient of resonant frequency (τ_f) of the (Ca_0.8Sr_0.2)(Sn_xTi_1?x)O₃ ceramics also improved with increasing Sn content.     

Dielectric properties of La2O3-doped Ba0.8Sr0.2TiO3 ceramics

La₂O₃-doped Ba_0.8Sr_0.2TiO₃ dielectric ceramics were prepared by conventional solid state ceramic route. Scanning electron microscope was employed to observe the surface morphologies. The capacitance C and dielectric loss factor D of the samples were measured with automatic LCR Meter 4225 at 10 kHz respectively. The results show that: ε _r of the samples decreases and tgδ first decreases then increases with increasing amount of La₂O₃ doping. ε _r reaches better value, tgδ obtains the minimum value at 0.5 mol% La₂O₃. ε _r increases and tgδ decreases when sintering temperature increases. The samples doped with 0.5 mol% La₂O₃ sintered at 1,350 °C for 10 h exhibited attractive properties, including high relative dielectric constant (>4,000), low dielectric loss (16.8 × 10^?4), low temperature coefficient of relative dielectric constant(<±21 %) in the temperature range of +25 to +85 °C.     

Studies on semiconductive (Ba0.8Sr0.2) (Ti0.9Zr0.1)O3 ceramics

In order to produce semiconductive (Ba_0.8Sr_0.2) (Ti_0.9Zr0.1)O₃ ceramics (BSZT), providing low resistivity for boundary-layer capacitor applications, a controlled valency method and a controlled-atmosphere method were applied and studied. In the controlled-valency method, trivalent ions (La³⁺ Sb³⁺) and pentavalent ions (Nb⁵⁺, Sb⁵⁺, Ta⁵⁺) were doped into BSZT ceramics, while in the controlled-atmosphere method, samples were sintered in air and a reducing atmosphere. The doped BSZT ceramics sintered in the reducing atmosphere showed much lower resistivities and smaller temperature coefficient of resistivity (TCR) than those sintered in air, indicating that low partial pressure of oxygen will increase the solubility of the donor dopant and enhance the grain growth. In addition, a small negative TCR at low temperature, as well as a small positive TCR at higher temperature, are also observed for specimens fired in a reducing atmosphere. The former is attributed to the semiconductive grain and the latter to the small barrier layer formed at the grain boundary.     

Effect of Zr+4 ion substitution on the structural, dielectric and electrical properties of Sr5LaTi3Nb7O30 ceramics

Polycrystalline Zr-modified Sr₅LaTi₃Nb₇O₃₀ compound was prepared by a high-temperature solid-state reaction technique. X-ray structural analysis confirmed the formation of compound in an orthorhombic system at room temperature. Detailed studies of the dielectric parameters (dielectric constant and tangent loss) as a function of frequency (1–100 kHz) at different temperature (150 to 650 K) were carried out. It was found that as Zr⁺⁴ concentration increases in Sr₅LaTi_{3 – x} ZrxNb₇O₃₀, the value of dielectric constant decreases. These compounds show ferroelectric-paraelectric phase transition of diffuse type at 283, 305 and 320 K for x = 0, 1 and 2 respectively. The transition temperature (T _c) shifts towards higher temperature and maximum dielectric constant value (_max) decreases with increasing Zr⁺⁴ concentration for x = 0 to x = 2. When Ti⁺⁴ cations were completely replaced by Zr⁺⁴ cations (i.e., Sr₅LaZr₃Nb₇O₃₀), the compound does not show any phase transition. Impedance-spectroscopic studies provided an insight into the electrical properties and understanding of relaxation behavior of the material. Measurement of electrical conductivity as a function of temperature suggests that the compounds have a negative temperature coefficient of resistivity (NTCR) with a typical semiconductor behavior.     

Sintering and dielectric properties of Sr(Bi2Ta2)0.95Ti0.2O9 ceramics

In this study, TiO₂ is used to substitute the Bi₂O₃ and Ta₂O₅ sites of the SrBi₂Ta₂O₉ ceramics to form Sr(Bi₂Ta₂)_0.95Ti_0.2O₉ composition. From the X-ray patterns, the 2θ values shift to higher values as the sintering temperatures increase. At lower sintering temperatures of 1200–1250 °C, the Sr(Bi₂Ta₂)_0.95Ti_0.2O₉ ceramics reveal a two-phase structure, bar-typed grains and disk-typed grains coexist; when 1300 °C is used as the sintering temperature, only the bar-typed grains are revealed. The sintering temperatures also have large influences on the maximum dielectric constants and the Curie temperatures of Sr(Bi₂Ta₂)_0.95Ti_0.2O₉ ceramics.     

Effects of sintering time on crystal structure,dielectric properties and conductivity of (Ca0.8Sr0.2)ZrO3 ceramics

(Ca_0.8Sr_0.2)ZrO₃ ceramics were prepared using solid-state reaction process, which were sintered at 1,480 °C for different sintering time (2, 4, 6, 8, 10, 12 h, respectively), their structures were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Rietveld refinement for the (Ca_0.8Sr_0.2)ZrO₃ sintered for 10 h was carried out by powder XRD at room temperature and it crystallizes in orthorhombic space group Pnma [a = 5.77341(4) Å, b = 8.05569(6) Å, c = 5.63318(4) Å and V = 261.9920(30) Å³, Z = 4]. The (Ca_0.8Sr_0.2)ZrO₃ ceramics sintered at 1,480 °C for 2–12 h possessed a dielectric constant (ε _r) of 23.6–27.9, a quality factor (Q × f) of 2,160–21,460 GHz and a temperature coefficient of resonant frequency (τ _f ) from ?14 to +13.6 ppm/°C. The Arrhenius plot of the dc electrical conductivity changed significantly with increasing sintering time.     

Effect of Sb5+ substitution on the dielectric properties of Ba3LiTa3Ti5O21 ceramics

The effects of substitution Sb for Ta on the sintering behavior and the microwave dielectric properties of Ba₃LiTa₃Ti₅O₂₁ ceramic were studied. Single-phase polycrystalline microwave dielectric ceramics Ba₃LiTa_3?x Sb _x Ti₅O₂₁(x = 0–3) were prepared by the solid-state reaction method. The sintering behavior and microwave dielectric properties of Ba₃LiTa_3?x Sb _x Ti₅O₂₁ ceramics were found to be affected by Sb substitution for Ta. With the increasing Sb content, the densified (>95 % of their theoretical X-ray density) temperatures of Ba₃LiTa_3?x Sb _x Ti₅O₂₁ ceramics increased from 1,160 to 1,220 °C, the dielectric constant (ε _r ) decreased from 55.5 to 27, and the Q × f value enhanced significantly from 18,480 to 29,400 GHz, with τ _f improving from 70 to ?25 ppm/°C. A near zero τ _f value could be obtained by carefully adjusting the Sb content.     

Influence of Bi2O3 addition on structure and dielectric properties of Ag(Nb0.8Ta0.2)O3 ceramics

The structure and dielectric properties of perovskite Ag(Nb_0.8Ta_0.2)O₃ ceramics were explored. A small amount of Bi₂O₃ was used to modify the dielectric properties of the ceramics. The addition of Bi₂O₃ led the ceramics to a high densification and optimal dielectric properties. With the addition of 4.5 wt% Bi₂O₃, the permittivity of Ag(Nb_0.8Ta_0.2)O₃ ceramics increased from 470 to 733, the dielectric loss decreased from 62×10^?4 to 6.7×10^?4, and the temperature coefficient of capacitance, TCC, decreased from 2004 ppm/°C to ?50 ppm/°C. The high permittivity obtained was due to the high densification and weak Ta-O or Nb-O bond strength in the oxygen octahedron that results from the addition of Bi₂O₃.     

Effects of Ca and Sr substitution on dielectric properties in ceramics

Modification of dielectric characteristics for Ba₃Sm₃Ti₅Ta₅O₃₀ was performed by Ca and Sr substitution for Ba. The temperature coefficient of the dielectric constant () of Ba₃Sm₃Ti₅Ta₅O₃₀ decreased somewhat by Ca substitution, but the dielectric constant () decreased considerably. In the case of Sr substitution, the temperature coefficient could be markedly decreased without considerable decrease of dielectric constant. Ceramics of the two series could obtain dielectric properties of high (> 100) and low loss (10^–3 at 1 MHz).     

The influences of particle sizes on the dielectric properties of PEI/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 composites

In order to investigate the embedded capacitors with higher capacitance value in the future, two technologies of increasing the dielectric constant of filler and decreasing the thickness of capacitors can be combined to develop a best method. For that, the high dielectric constant of (Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (BSTZ) ceramic powders with three different sizes (3 microm, 200 nm, and 100 nm) are used as the filler to mix with polyetherimide (PEI) to form the PEI/BSTZ composites. The dielectric constants and loss tangents of PEI/BSTZ composites with different contents of BSTZ ceramic powders are measured using the plate method. As the contents of BSTZ powders increase from 10 wt% to 70 wt%, the dielectric constants and loss tangents of PEI/BSTZ composites increase with the increase content of BSTZ ceramic powders, independent on the particle sizes. As the BSTZ content is less than and equal to 50 wt% and same loading ratio is used, the dielectric constants of PEI/200 nm-BSTZ and PEI/100 nm-BSTZ composites are large than those of PEI/3 microm-BSTZ composites. In this study, the Lichtenecker logarithmic mixing rule is also used to fit the measured results and predict the dielectric constants of PEI/BSTZ composites.     

Microwave dielectric properties of Sr2Ce2Ti5O16 ceramics

Sr₂Ce₂Ti₅O₁₆ dielectric ceramics were prepared by conventional solid-state ceramic route. The structure and microstructure of the ceramics were investigated by X-ray diffraction and scanning electron microscopic methods. The Sr₂Ce₂Ti₅O₁₆ has a psuedocubic structure. It has ɛ_r of 113, unloaded quality factor (Q_u × f) of 8000 GHz and temperature coefficient of resonant frequency of 306 ppm/°C. The effects of various dopants on the structure, microstructure and microwave dielectric properties of the material have been investigated. It is found that addition of small amount of dopants such as PbO, Al₂O₃, Nd₂O₃, MoO₃, CeO₂, La₂O₃, Fe₂O₃ and NiO improve the microwave dielectric properties of Sr₂Ce₂Ti₅O₁₆.     

低损耗( Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4陶瓷的微波介电性能研究

采用标准电子陶瓷工艺制备了(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4陶瓷.研究了(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4陶瓷的烧结特性、相结构和微波介电性能.采用X射线衍射分析其物相组成,利用SEM观察其显微结构.XRD图谱表明烧结样品为立方尖晶石( Mg0.95Zn0.05)2(Ti...     

Oxygen vacancies-related high-temperature dielectric relaxation and pyroelectric energy harvesting in lead-free Ba(Zr0.2Ti0.8)O3 ceramics

Journal of Materials Science: Materials in Electronics - Ba (Zr0.2Ti0.8) O3 ceramics were prepared by a sol–gel process. Temperature-dependent dielectric permittivity εγ and loss...