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Simultaneous realization of broad temperature stability range and outstanding dielectric performance in (Ag+, Ta5+) co–doped TiO2 ceramics
摘要： Effects of sintering condition on dielectric properties and microstructure were systematically investigated in (Ag1/4Ta3/4)0.005Ti0.995O2 ceramics. A giant dielectric constant of ~9831 (1 kHz) and a relatively low dielectric loss of ~0.041 (1 kHz) were realized at the optimal sintering condition of 1330 °C with a holding time for 10 h. Notably, stable temperature coefficient (within -6.8% to 8.8%) of the dielectric constant at 10 kHz was achieved in a broader temperature range (-200–200 °C), which shows superior temperature stability of our sample than the application requirements (-55~200 °C and ?εr/ε25 °C < ±15%) of commercial X9R capacitor.
关键词： sintering conditions,dielectric properties,ceramics,temperature stability
更新于2025-09-23 15:23:52
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Synthesis of Eu2O3 doped BaO-TiO2-GeO2 based glass-ceramics: Crystallization kinetics, optical and electrical properties
摘要： Eu3+ doped transparent glass-ceramics (GCs) containing non-centrosymmetric ferroelastic Ba2TiGe2O8 (BTG) crystals as the major crystalline phase have been synthesized. BTG crystal phase was generated in the glass matrix with mole percent composition 30BaO-15TiO2-55GeO2 synthesized by melt quenching technique followed by controlled crystallization through ceramming heat-treatment. A di?usion controlled surface crystallization event with zero and constant nucleation rates was determined through a comparative study of some linear and nonlinear solid state reaction models. Nonlinear crystallization kinetics studies facilitated determination of the experimental ceramization temperature and time for fabrication of transparent glass-ceramics containing BTG nanocrystals. XRD, FTIR, TEM and FESEM measurements con?rmed the dispersion of BTG nanocrystals of size 20–100 nm in the glass matrix. Local crystal environment around Eu3+ ions facilitated the enhancement of photoluminescence of glass-ceramics with respect to the precursor glass. High dielectric constant, low loss and dissipation factors were observed for the GCs.
关键词： Refractive index,Glass-ceramics,Photoluminescence,Dielectric properties,Crystallization kinetics,Hysteresis loop
更新于2025-09-23 15:23:52
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Excellent thermal-stability and low dielectric loss of BaTiO3-Bi(Sr2/3Nb1/3)O3 solid solution ceramics in a broad temperature range applied in X8R
摘要： (1?x)BaTiO3-xBi(Sr2/3Nb1/3)O3 [(1?x)BT-xBSN, 0.02 ≤ x ≤ 0.1] ceramics were synthesized by a traditional solid state reaction technique. The transition from tetragonal phase to pseudo cubic phase at 0.02 ≤ x ≤ 0.04 was observed in Raman spectra and X-ray di?raction patterns. As the BSN contents increased, the grain size increased. With adding Bi(Sr2/3Nb1/3)O3, the thermal stability of permittivity and dielectric loss of ceramics got a good optimization. Especially, 0.9BT-0.1BSN ceramics have small Δε/ε25°C values (≤ ± 15%) in a wide temperature range of ?75 °C to 153 °C, high relative permittivity (～1505 to 1700) and low dielectric loss (tan δ ≤ 0.02) from ?88 °C to 200 °C, showing that BT-BSN ceramics are suitable for using in MLCCs of X8R. Impedance spectroscopy was analyzed the conduction and relaxation processes. The results showed that the relaxation and the conduction process in the high temperature region are thermally activated, and the oxygen vacancies are charge carriers.
关键词： Thermal stability,Dielectric properties,Impedance,Phase evolution
更新于2025-09-23 15:23:52
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Dielectric and Transport Properties of Strontium Modified Calcium Copper Titanate
摘要： The present article provides the detailed study of the effect of strontium on the structural, microstructural, dielectric and electrical characteristics of strontium modified calcium copper titanate (i.e. Ca0.95Sr0.05Cu3Ti4O12, referred as CSCTO further) synthesized by a cost-effective ceramic processing technology. The structural analysis carried out suggests a cubic symmetry in the prepared sample. The dielectric relaxation and electrical conduction mechanism of CSCTO were studied using various powerful spectroscopic tools (i.e dielectric and impedance). Study of temperature dependence of dielectric permittivity exhibits very high (giant) dielectric permittivity (5 (cid:1) 103) and low loss factor at low frequency (1 kHz) at an intermediate temperature (315 (cid:3)C). Structure–properties relationship and conduction mechanism have been studied in a wide frequency (103–106 Hz) and temperature (25–315 (cid:3)C) range. At region of low frequency and high temperatures, there is a dominant role of the interface and Maxwell–Wagner dielectric relaxation mechanism in CSCTO bulk ceramic. The grain, grain boundary and electrode contributes towards the capacitive and resistive property of the sample are discerned from Nyquist plot. The ferroelectric (P–E) loop of the sintered CSCTO bulk sample at room temperature showed a lossy hysteresis loop. These findings further promote the capabilities of CSCTO as a base for supercapacitor.
关键词： X-Ray diffraction,supercapacitor,ferroelectric phase,microstructure,dielectric properties
更新于2025-09-23 15:23:52
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Temperature independent low firing [Ca0.25(Nd1-xBix)0.5]MoO4 (0.2 ≤ x ≤ 0.8) microwave dielectric ceramics
摘要： A scheelite structured [Ca0.25(Nd1-xBix)0.5]MoO4 (0.2 (cid:1) x (cid:1) 0.8) ceramics were prepared via solid state reaction method. All the ceramics can be well densi?ed below 780 (cid:3)C. As x value increased from 0.2 to 0.8, microwave dielectric permittivity increased from 14.0 to 27.8, Qf (Q ? quality factor ? 1/dielectric loss; f ? resonant frequency) value decreased from 42,000 GHz to 19,000 GHz, and TCF shifted from (cid:4)50 ppm/oC to t18 ppm/oC. The best microwave dielectric properties with permittivity between 23.54 and 23.56, Qf value between 24,000 GHze21,000 GHz and TCF value ~ (cid:4)8 ppm/oC in wide temperature range 25 (cid:3)Ce130 (cid:3)C were obtained in x ? 0.6 ceramic. This work showed that Bi played an important role to modify the TCF from negative to positive value in scheelite materials and this result further accelerate the application of scheelite materials in low temperature co-?red ceramics (LTCC) technology.
关键词： Microwave dielectric properties,Low temperature sintering,MoO3,Scheelite
更新于2025-09-23 15:23:52
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Li- and Mg-codoped bismuth niobate pyrochlores: Synthesis, structure, electrical properties
摘要： The structure and conductivity of the new Li- and Mg-codoped bismuth niobates Bi1.5Mg1?xLixNb1.5O7?δ (0 ≤ x ≤ 0.50) with the pyrochlore structure have been investigated. The samples were synthesized by the method of organic-inorganic precursors combustion. A structural characterization was performed using 7Li nuclear magnetic resonance (NMR) spectroscopy in combination with the ?tting of X-ray di?raction patterns. The Li+ cations dynamics were studied by temperature-dependent 7Li NMR lineshape analysis. The measurements have shown that the Li+ cations are distributed in one of two possible sublattices in the structure and are not mobile up to 120 °C. According to the results of structural analysis of the Bi1.5Mg1?xLixNb1.5O7?δ (x = 0.25; 0.50) pyrochlores the lithium atoms are distributed in the bismuth sites. The electrical properties were investigated by impedance spectroscopy method in the air, oxygen and “wet” atmospheres in the 25–750 °C temperature range. The activation energy value of dc conductivity is about 1.2–1.3 eV for the all samples and corresponds to the ionic (oxygen) conductivity at T > 400 °C. Electronic (p-type) conductivity was determined at T < 360 °C. 1H MAS NMR data and the results of the comparison of the conductivity of Li- and Mg-codoped bismuth niobates in dry and “wet” atmospheres point to the proton conductivity up to 500 °C. The dielectric permittivity ε′ values increase with lithium content from 86 (x = 0) to 143 (x = 0.5) at the same dielectric loss tanδ = 0.002 (1 MHz, 25 °C), TCC values vary from ?590 to ?530 ppm/°C in the 25–280 °C temperature range.
关键词： Conductivity,Dielectric properties,Pyrochlore,Dopant distribution,NMR spectroscopy,Bismuth niobate
更新于2025-09-23 15:23:52
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Structural and dielectric properties of prepared PbS and PbTe nanomaterials
摘要： In this work, PbS and PbTe nanomaterials with various morphologies were synthesized by a hydrothermal method. The structural properties were investigated by using X-ray diffraction (XRD) and corresponding scanning electron microscopy together with their EDX analysis. Both the PbS and PbTe nanomaterials possess good polycrystalline structure. The crystallite size, determined from the XRD data, of PbS is 5 nm whereas the corresponding value of PbTe is 2.69 nm. SEM micrographs reveal that the prepared PbS nanomaterial has star-shaped structures, micro-flowers, some cubes, and semi-dendrites, whereas PbTe has semi-flower structures. Additionally, the dielectric properties have been studied in a broad frequency range from 0.1 Hz up to 1 MHz at temperatures from 298–423 K. The real and imaginary parts of the complex dielectric constant ε' and ε'' of PbTe are comparatively higher than those of PbS. Moreover, the dielectric data were analyzed on the basis of the electric modulus.
关键词： electric modulus,PbS,EDX,PbTe,dielectric properties,SEM
更新于2025-09-23 15:23:52
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Effect of processing conditions on (Ba1-xCax)(Ti0.9Sn0.1)O3 lead-free ceramics for the enhancement of structural, humidity sensing and dielectric properties
摘要： The present study reports detailed guidelines for the preparation of high-quality perovskite (Ba1-xCax)(Ti0.9Sn0.1)O3 (BCTS) (x = 0.0–0.1) lead-free ceramics by solid state reaction. The compositions (x = 0.0–0.04) exhibit orthorhombic–tetragonal phase transition (TO-T), except x ≥ 0.06 that shows a pure tetragonal structure phase which conformed by X-ray diffraction (XRD). The microstructure and purity of the sintered ceramics were examined using scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS). Some pores existing in the grain boundary were observed at high concentrations of Ca content. Field emission scanning electron microscope (FE-SEM) was used to examine the morphology of sensing film of the calcined powder and it was prepared as a humidity sensor using screen-printing technique. All the compositions exhibited poor sensitivity toward the humidity sensing in the range of 0–98% RH at room temperature. Hot-stage microscope (HSM) has been used to investigate the sintering curve of the pure calcined powder and it was found that the suitable sintering temperature for obtaining a fully dense microstructure is 1400 °C. The highest values of permittivity (εr = 46,515, at 10 kHz) and piezoelectric coefficient (d33 = 510 pC/N) were achieved in the composition x = 0.02. The difference between alumina and platinum crucibles for the processing of the powders has been introduced, and by the aid of dispersive spectrometer analysis and it was indicated that use of alumina crucibles leads to the undesired presence of Al in the ceramics, which can be prevented by using a capped platinum crucibles.
关键词： Lead-free ceramics,Humidity sensing,Phase formation,Processing,Dielectric properties
更新于2025-09-23 15:23:52
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</sub> ) Interlayer
摘要： Electrical and dielectric properties of Au/n-Si metal–semiconductor structures with high dielectric have been examined by capacitance/conductance–voltage (C/G–V) measurements in the frequency range of 5–500 kHz at room temperature. Voltage-dependent profiles of interface states (Nss) and resistance (Ri) were extracted from the C and G data using the low–high-frequency capacitance and Nicollian–Brews methods, respectively. The real and imaginary components of the complex dielectric constant (ε', ε''), electric modulus (M', M''), and ac conductivity (σac) were calculated from the C and G data. All parameters have a strong relation with frequency and voltage, especially at low frequencies due to Maxwell–Wagner relaxation and Nss. The observed peaks in the Nss–V and Ri–V plots can be ascribed by the special distribution of Nss at M/S interface. These results confirmed that [2% graphene cobalt-doped (Ca3Co4Ga0.001Ox)] interlayer has high-dielectric constant and can be used an interlayer instead of the traditional SiO2 at M/S interface to increase their capacitance or more charges/energy storage and reduce both the values of Nss and series resistance (Rs). The values of σ are almost constant at lower–intermediate frequencies, but they start to increase at high frequencies that are corresponding to the dc and ac conductivity, respectively.
关键词： electrical properties,nanostructures,Dielectric properties,graphene,polymer
更新于2025-09-23 15:22:29
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Temperature-Dependent Phase Transition in Orthorhombic [011]c Pb(Mg1/3Nb2/3) O3-0.35PbTiO3 Single Crystal
摘要： Relaxor [011]c PMN-0.35PT single crystal phase transition characteristics are investigated through various methods including variable temperature dielectric properties, X-ray diffraction, bipolar ferroelectric hysteresis loops (P-E) and electric-field-induced strain (S-E) hysteresis loops measurements. The results reveal that two phase transitions exist within the range from room temperature to 250 °C: orthorhombic (O)-tetragonal (T)-cubic (C). The O-to-T and T-to-C phase transition temperatures have been identified as 84 °C and 152 °C, respectively. Diffuseness degree of the T-to-C phase transition for the unpoled single crystal has been calculated to be 1.56, implying an intermediate state between normal and relaxor ferroelectrics. Temperature-dependent remanent polarization (Pr), coercive field (Ec), saturation polarization (Ps), hysteresis loop squareness (Rsq), and longitudinal piezoelectric constant (d*33) are also explored to learn the details of the phase transitions. Variable temperature unipolar Suni-E hysteresis loops avail additional evidence for the microstructure change in the as-measured single crystal.
关键词： temperature-dependent phase transition,S-E hysteresis loops,P-E hysteresis loops,orthorhombic [011]c PMN-0.35PT,dielectric properties,piezoelectric properties
更新于2025-09-23 15:22:29