Temperature Coefficient Of Relative Permittivity Research Articles

Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

In this paper, a novel low-temperature sintering substrate for low temperature co-fired ceramic applications based on indialite/cordierite glass ceramics with Bi2O3 as a sintering aid showing low permittivity (εr) and ultralow dielectric loss (tan δ) is described. The fine powder of indialite was prepared by the crystallization of cordierite glass at 1000 °C/1 h. The optimized sintering temperature was 900 °C with 10 wt % Bi2O3 addition. The relative density achieved was 97%, and εr and tan δ were 6.10 and 0.0001 at 1 MHz, respectively. The composition also showed a moderately low temperature coefficient of relative permittivity of 118 ppm/°C at 1 MHz. The obtained linear coefficient of thermal expansion was 3.5 ppm/°C in the measured temperature range of 100 to 600 °C. The decreasing trend in dielectric loss, the low relative permittivity at 1 MHz, and the low thermal expansion of the newly developed composition make it an ideal choice for radio frequency applications.

Variation of Dielectric and Electrical Properties of Zr-Substituted Lead Calcium Iron Niobate with Temperature and Frequency

The purpose of the present study is to improve the dielectric properties of lead calcium iron niobate with Zr substitution, and to make it suitable for multilayer capacitor applications in resonant circuits. (Pb0.45Ca0.55)(Fe0.5Nb0.5)1−y ZryO3 dielectric ceramics where y varies from 0.00 to 0.15 in steps of 0.03, that have been synthesized by the columbite precursor method. Dielectric and electrical properties were measured as a function of frequency (10 kHz to 1 MHz) and temperature. Two frequency dependent anomalies were observed in relative permittivity (er) versus temperature (T) plots around 375 K and between 500 K and 575 K. The temperature coefficient of relative permittivity, (τe) has been improved with the substitution of (Fe0.5Nb0.5)4+ ions by Zr4+ ions at B-sites. The single semicircle, observed in Nyquist plots at different temperatures, suggests a single relaxation process in the synthesized samples. The activation energies obtained from different dependences are found to be approximately comparable.

Mechanical and electrical properties of Bi1.5-xLaxZn0.92Nb1.5O6.92 pyrochlore ceramics

The physical properties of Bi1.5-xLaxZn0.92Nb1.5O6.92 solid solutions are investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS), and temperature dependent relative permittivity and electrical resistivity measurements. The La content which was varied from 0.10 to 0.60 is found to be solvable up to 0.21. Further increase in the amount of the La content caused the appearance of Bi0.4La0.6O1.5, LaNbO4, and ZnO minor phases in the pyrochlore matrix. While the lattice parameter and the theoretical, bulk and relative density are hardly affected by the increase in the La content, the strain, the dislocation density and the crystallite size are remarkably varied. The relative permittivity and temperature coefficient of relative permittivity are found to be sensitive to the La-Content. The electrical resistivity is observed to be temperature invariant below 390 K. It exhibits an insulator-semiconductor transition property at a critical temperature that increases with the increasing La content. Such observation is assigned to the increase in the dislocation density, which arises from the increment in the La content. The activation energies of the doped ceramics, which are determined from the electrical resistivity analysis are found to be ~ 1.12-1.00 eV.

Frequency and Temperature Dependence of Dielectric and Electrical Properties of Sn-Doped Lead Calcium Iron Niobate

Sn-substituted lead calcium iron niobate specimens with general formula (Pb0.45Ca0.55)(Fe0.5Nb0.5)1−y Sn y O3 with 0.00 ≤ y ≤ 0.15 in steps of 0.03 have been synthesized using a two-stage method. The x-ray diffraction patterns for all the synthesized samples reveal a perovskite structure with pseudocubic symmetry. A small amount of pyrochlore phase was obtained along with the perovskite phase, decreasing with increasing Sn content up to y = 0.09. The temperature and frequency dependence of the dielectric and electrical properties of Sn-substituted lead calcium iron niobate were studied. Two dielectric anomalies were observed in e r–T plots for all the samples due to generation of oxygen vacancies. The temperature coefficient of relative permittivity, τ e , decreased with increasing Sn content. The single, semicircular arc observed in Nyquist plots suggests a single relaxation process. The activation energies obtained from the temperature dependence of the relaxation time and grain resistance were found to be approximately comparable.

Microwave dielectric properties of pure and Zr4+ doped lead calcium iron niobate substrates for microwave devices and antenna applications

ABSTRACTTwo series of (Pb1‐xCax)(Fe0.5Nb0.5)O3 for x = 0.00, 0.20, 0.40, 0.45, 0.50, 0.55, 0.60, and (Pb0.45Ca0.55)(Fe0.5Nb0.5)1‐yZryO3 for 0.00 ≤ y ≤ 0.15 in the steps of 0.03 have been synthesized using columbite precursor method. X‐ray diffraction patterns show that all the solid solutions have tetragonal symmetry. Microwave dielectric properties of synthesized solid solutions have been investigated in X‐band (8.2–12.4 GHz). The substitution of Zr4+ ions at B‐site of (Pb0.45Ca0.55)(Fe0.5Nb0.5)1‐yZryO3 decreased the loss tangent but did not remarkably affect the relative permittivity. The temperature coefficient of relative permittivity decreased with the substitution of Ca2+ ion for Pb2+ ions at A‐site in first series. The temperature coefficient of relative permittivity further decreased with the substitution of Zr4+ ions at B‐site in second series. The reflection loss decreased but VSWR and bandwidth improved slightly with the substitution of Zr contents in second series. The present materials can be used as substrate for microwave devices and antennas applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2151–2155, 2015

A new HDPE/BST polymer–ceramic composite for wireless temperature sensing

A new HDPE (high density polyethylene)/BST (BaSrTiO3) polymer ceramic composite was prepared with the extrusion processing technique, and its dielectric response in the microwave frequency range was investigated at different temperatures. For the 30vol% ceramic loaded HDPE/BST composite, as the temperature increased from 20°C to 80°C, the relative permittivity of the composite varied from 7.10 to 6.66, so the temperature coefficient of relative permittivity is −1033ppm/°C, and the temperature coefficient of the resonant frequency (τf) of the composite is about 440ppm/°C. Such a large temperature coefficient is suitable for wireless temperature sensing applications.

Low Dielectric Loss Polymer-Ceramic Composites for Wireless Temperature Sensation

The low dielectric loss polymer-ceramic composites with high density polyethylene (HDPE) as matrix and BaO-Nd2O3-TiO2(BNT) as filter for wireless temperature sensation were prepared by an extrusion processing technique. For 30vol % ceramic loaded HDPE, as the ambient temperature increases from 30 to 100 °C, the relative permittivity and loss tangent of the composite vary from 6.25 to 6.09 and from 0.004 to 0.011 respectively, and the temperature coefficient of relative permittivity is -370ppm/°C. By using this composite as the patch microstrip antenna substrate, a simple UHF RFID temperature sensor antenna is fabricated and measured. The experimental results show that a 2MHz/10°C frequency increment can be obtained at 900 MHz in the temperature range from 25 to 100°C.

Phase equilibria and dielectric properties of Bi3+(5/2)xMg2−xNb3–(3/2)xO14−x cubic pyrochlores

Subsolidus pyrochlores with the proposed formula, Bi3+(5/2)xMg2−xNb3−(3/2)xO14−x (0.14≤x≤0.22) were successfully synthesised at the firing temperature of 1025°C using conventional solid-state reaction. The excess Bi3+ charge was offset by removal of relative proportion of Mg2+ and Nb5+ together with creation of oxygen non-stoichiometry in order to preserve electroneutrality of the system. These samples were crystallised in cubic structure with space group of Fd3m, No. 227 and their refined lattice parameters were in the range of 10.5706 (3)–10.5797 (7)Å. The surface morphologies of the samples as confirmed by scanning electron microscopy analysis were of irregular shaped grains while their crystallite sizes of ~30–85nm were calculated using the Scherrer equation and the Williamson–Hall method. No thermal event was discernable indicating these pyrochlores were thermally stable within a studied temperature range of ~30–1000°C. The recorded dielectric constants of Bi3+(5/2)xMg2−xNb3−(3/2)xO14−x (0.14≤x≤0.22) subsolidus pyrochlores were generally above ~160 and their dielectric losses were in the order of 10−4–10−3 at the frequency of 1MHz and temperature of ~30°C. Meanwhile, these ceramic samples also exhibited negative temperature coefficient of relative permittivity between −528 and −742ppm/°C in the temperature range of ~30–300°C.

Reconfigurable Sensing Antenna With Novel HDPE-BST Material for Temperature Monitoring

A UHF-band reconfigurable sensing antenna (RSA) with temperature sensation function is presented in this letter. In order to obtain a high sensitivity, a novel composite material-namely, high-density polyethylene Ba0.3Sr0.7TiO3 (HDPE-BST)-is developed to have a large temperature coefficient of relative permittivity, which varies from 7.10 at 20°C to 6.66 at 80°C. This material is directly integrated into a patch RSA design as substrate. Thus, the RSA frequency is reconfigured by the environmental temperature. To increase the temperature sensitivity, the bandwidth of RSA should be as narrow as possible. To this end, a patch RSA resonating at 900 MHz is designed, with a 3-dB gain bandwidth of only 5.4 MHz (0.6%). The experimental results show that an 8 MHz/10°C frequency increment can be obtained in the temperature range from 20°C to 80°C.

Studies on intermolecular interactions in (nitrobenzene + alkoxyethanol) binary mixtures by relative permittivity measurements at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K

Relative permittivities, at T=(293.15, 298.15, 303.15, 308.15, and 313.15)K, in the binary mixtures of nitrobenzene with 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, and 2-butoxyethanol have been measured as a function of composition. From the experimental results, the deviations in the relative permittivity at T=(293.15, 298.15, 303.15, 308.15, and 313.15)K and the excesses of temperature coefficient of relative permittivity at T=298.15K from a mole fraction average have been calculated. The results are discussed in terms of intermolecular interactions and structure of studied binary mixtures.

Frequency and field dependence dielectric properties of novel composites fabricated from (Sr 1− xPb x)TiO 3: Al 2O 3 component phases

Composites fabricated from (Sr 1− x Pb x )TiO 3 (SPT) and Al 2O 3 are developed that show relative permittivity ∼100, tangent δ less than 0.005, and temperature coefficient of relative permittivity ∼700 ppm at a low frequency, 10 kHz over the range ∼150–40 °C. A dielectric tunability of ∼5% at 20 kV/cm field is maintained over the whole temperature range. X-ray diffraction reveals that after the fabrication, the second phase is not Al 2O 3 but a composite of alternative phases in conjunction with SPT, which presumably contributes the tunability.

Acetonitrile - 2-Methyl-Propan-1-ol and Acetonitrile - 2-Methyl-Propan-2-ol Binary Mixtures and their Physicochemical Properties

The 1 H-NMR spectra of liquid binary mixtures of acetonitrile with 2-methyl-propan-1-ol (i-BtOH) and 2-methyl-propan-2-ol (t-BtOH), were recorded at 298 K over almost the whole range of mixed solvent compositions. From these data the values of spectral parameters, j i (ACN-i-BtOH) and j i (ACN-t-BtOH) were found. The relative permittivities ( k 12 ) and the densities ( d 12 ) of the mixed solvents were measured at 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K. The experimental data were used to test some empirical equations of the type: y 12 = y 12 ( t ) and y 12 = y 12 ( X 1 ) [where: y 12 = d 12 or k 12 ]. From all these data, the deviations from ideality molar volumes , temperature coefficients of relative permittivities ( f 12 ) and the excess extrathermodynamic parameters were calculated. The values of these structural parameters are discussed in terms of interactions of acetonitrile with both alcohols.

Volumetric and dielectric behaviour of 2-methoxyethanol-dimethylsulfoxide binary liquid mixtures

Densities (d 12) and relative permittivities ( ϵ 12) have been measured for 2-methoxyethanol (ME) with dimethylsulfoxide (DMSO) binary liquid mixtures over the whole composition range at various temperatures ranging from 288.15K. The experimental data were used to test some empirical equations of the type: y 12 = y 12(t) and y 12 = y 12(X 1) and [where: y 12 − d 12 or ϵ 12]. From all these data, the excess molar volumes (V 12 E), temperature coefficients of relative permittivities ( α 12) and the excess extrathermodynamic parameters ϵ 12 E were calculated. The 1H-NMR spectra of liquid binary mixtures of ME and DMSO, were recorded at 298 K over almost the whole range of the mixed solvent compositions. From these data the values of the spectral structural parameters were found, Δδ(ME-DMSO). These structural parameters as a function of concentration suggest the formation of stable 2ME· DMSO and ME·DMSO intermolecular complexes.

H-NMR Spectral and Dielectric Behaviours of the 2-Metoxyethanol-Tetrahydrofuran Solvent System

Relative permittivities (E 12) have been measured for 2-metoxyethanol (ME)-tetrahydrofuran (THF) binary liquid mixtures over the whole compositions range at various temperatures ranging from 291.15 K to 308.15 K. The experimental data were used to test some empirical equations of the type: y 12 = y 12(t) and y 12 = y 12 (X 1) [where: y 12-E 12]. From all these data, the temperature coefficients of relative permittivities (α12) and the excess extrathermodynamic parameters εE were calculated. The 1H-NMR spectra of liquid binary mixtures of ME and THF, were recorded at 298 K over almost the whole range of the mixed solvent compositions. From these data the values of the values of the spectral structural parameters were found, δδ(ME-THF). These structural parameters as a function concentration suggest the formation of stable 3ME.THF types intermolecular complexes.

2-Metoxyethanol-Acetonitrile Binary Mixtures and Their Physicochemical Properties

Densities (d 12) and relative permittivities (\\Varepsilon12) have been measured for 2-metoxyethanol (ME) and acetonitrile (ACN) binary liquid mixtures over their whole compositions ranges at various temperatures ranging from 288.15K to 308.15K. The experimental data were used to test some empirical equations of the type: y 12=y 12(t) and y 12=y 12(X 1) (where: y 12-d 12 or \\Varepsilon12). From all these data, the excess molar volumes (V E m), temperature coefficients of relative permittivities (α12) and the excess extrathernmodynamic parameters \\VarepsilonE were calculated. The 1H-NMR spectra of liquid binary mixtures of ME and ACN, were recorded at 298 K over almost the whole range of the mixed solvent compositions. From these data the values of the values of the spectral structural parameters were found, Δδ(ME-ACN). The values of these structural parameters are discussed in terms of interactions of 2-metoxyethanol with acetonitrile.

Forsterite-based Ceramics for Microwave Application with Low Loss and Low Temperature-Coefficient of Relative Permittivity.

The forsterite-based ceramics doped with CaTiO3 and MgAl2O4 was developed to decrease the temperature dependence of dielectric permittivity. Doping of CaTiO3 into forsterite decreased the temperature coefficient of relative permittivity, TCe, and changed the sign of TCe. When 6mol% and 20mol% of CaTiO3 was doped, the values of TCe were 104 and-129 ppm/K, respectively. However, the values of tan6 increased to 1.8×10-3, and 3.6×10-3, respectively, because of the nucleation of titanite crystals with larger dielectric loss. Further addition of MgAl2O4 lowered the value of tanδ as low as 4×10-4. The decrease in tand may be attributed to the decomposition of titanite crystals by the reaction between spinel and titanite.

Studies on Associated Solutions. Part II. Physicochemical Properties of Acetonitrile-Propan-2-ol Mixtures

The 1H-NMR spectra of liquid binary mixtures of acetonitrile and propan-2-ol, were recorded at 298 K over almost the whole range of the mixed solvent compositions. From these data were found the values of the spectral parameter, Δδ(ACN-PrOH-2). The densities (d 12) and relative permittivities (ε12) of the mixed solvent were measured at 288.15K, 293.15K, 298.15K, 303.15K and 308.15K, as well as refractive indices at 298.15K. From all these data, the molar volumes (V m), temperature coefficients of relative permittivities (αn) and their deviations from ideality were calculated. Additionally, the Kirkwood's correlation factors (g K) were found. The values of these properties are discussed in terms of interactions of acetonitrile with propan-2-ol.

Study on intermolecular interactions in liquid acetonitrile — propan-1-ol mixtures by means of measuring their 1H-NMR spectra and analysis of their physicochemical properties

The 1H-NMR spectra of liquid binary mixtures of acetonitrile and propan-1-ol, were recorded at 298 K over almost the whole range of the mixed solvent compositions. From these data were found the values of the spectral parameter, Δδ(ACN PrOH). The densities (d 12) and relative permittivities (ɛ 12) of the mixed solvent were measured at 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K, as well as refractive indices at 298.15 K. From all these data, the molar volumes (V m), apparent molar volumes (V ,i), partial molar volumes (V i 0), temperature coefficients of relative permittivities (α 12) and their deviations from ideality were calculated. Additionally, the Kirkwood's correlation factors (g κ) were found. The values of these properties are discussed in terms of interactions of acetonitrile with propan-1-ol.

Physicochemical Properties of Acetonitrile-Butan-1-Ol and Acetonitrile-Butan-2-Ol Mixtures

The densities (d12 ) and relative permittivities (ϵ12) of liquid binary mixtures of acetonitrile-butan-l-ol and acetonitrile-butan-2-ol were measured at 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K, as well as refractive indices (n D 12) at 298.15 K and surface tensions (σ12) at 293.15 K, 298.15 K and 303.15 K. From all these data, the molar volumes (V m ), apparent molar volumes (V i, φ), temperature coefficients of relative permittivities (α12) and surface tensions (k) and their deviations from ideality were calculated. Additionally, the Kirkwood's correlation factors (g K ) were found. The values of these properties are discussed in terms of interactions of acetonitrile with butan-1-ol and butan-2-ol.

Phase Transformation and Temperature Dependence of Relative Permittivity for A-site Substituted Sr(Y 0.5 Ta 0.5 )O 3 Perovskites

A-site cation substitution with Ba2+ or Ca2+ ions was made for the ordered complex perovskite Sr(Y0.5Ta0.5)O3 to correlate the structure evolution and the change in the temperature coefficient of relative permittivity (TCer) with the cation substitution. The crystal symmetry of the solid solutions at room temperature changed as monoclinic → rhombohedral → cubic with the corresponding A-site cation species of Ca2+ → Sr2+ → Ba2+. On heating, the rhombohedral phase of Sr(Y0.5Ta0.5)O3 was firstly transformed to the cubic phase with a lower symmetry (F43m or F432) at 1000°C and further to the ideal cubic phase (Fm3m) at 1300°C. The similar phase transformation behavior at elevated temperatures was observed for each of the Ba2+-substituted perovskites, both the phase transformation temperatures being lowered with increasing Ba2+ content. TCer of the ordered perovskites monotonously increased over the temperature range where the phase transformation regions from monoclinic to rhombohedral or from rhombohedral to cubic (F43m or F432) occurred. On the other hand, a subtle symmetry change in the cubic phase from F43m (F432) to Fm3m caused a remarkable change in the TCer from positive to negative at the transformation temperature. These results suggested that the positive TCer is essentially correlated to the relaxation of the tilting of the BO6 octahedra in the perovskite structure on heating.