Dielectric Properties Of Sr Research Articles

Crystal Structure Modification and Dielectric Properties of Sr- and La-Containing A2B2O7 Thin Films for High-Temperature Operational Film Capacitors.

In order to obtain thermally stable thin-film materials with high dielectric constant, A2B2O7 thin films (Sr2Ta2O7, Sr2Nb2O7, La2Zr2O7, and La2Ti2O7) containing Sr or La and their solid solutions were grown on Pt/Ti/SiO2/Si substrates by RF sputtering and their crystal structures and dielectric properties were investigated. The Sr2Ta2O7 and La2Ti2O7 films exhibit highly oriented crystal structures. By contrast, the Sr2Nb2O7 and La2Zr2O7 films exhibit polycrystalline structures. The leakage properties of the Sr-containing films are lower and more stable in the high-temperature region (up to 300 °C) than those of the La-containing films. Among the investigated films, the Sr2Ta2O7 film grown at 500 °C and annealed at 900 °C shows the most stable dielectric constant with respect to temperature in the temperature range from room temperature to 300 °C. In addition, the xSr2Ta2O7-(1-x)La2Ti2O7 solid solutions exhibit enhanced dielectric properties at x = 0.35. The dielectric constant is greater than 100, and its variation with temperature is less than 10%. The Sr-containing A2B2O7 ferroelectric thin films have potential applications as high-temperature film capacitors that can operate at temperatures as high as 300 °C.

Influence of Ni2+ ions on structural, spectral and dielectric properties of Sr–Co spinel ferrites synthesized by sol-gel auto-combustion route

Nickel substituted Sr–Co nano spinel ferrites with composition Sr0.5-xNixCo0.5Fe2O4 (0.0, 0.1, 0.2, and 0.3) were prepared with the help of a sol-gel auto combustion route. The prepared materials were sintered at 800 for four and a half hours. Analysis of XRD confirmed that the material is composed of a cubic spinel structure with a single phase, and its space group is Fd-3m. Rietveld refinement of X-ray diffraction data was done for all prepared compositions using FULLPROF software. As the composition under study contains more nickel than lattice constant, crystalline size, X-ray density, and bulk density decrease. The dielectric properties were observed about frequency. The dielectric properties revealed that dielectric loss, dielectric constant, and ac conductivity decrease with increasing the Ni2+ content. The activation energy (ΔE) was calculated from the slope of Arrhenius plots. The ΔE found in the range of 0.580–0.096 eV. The analysis of XPS was carried out to examine the elemental state of annealed samples. The prepared material is suitable for employment in applications involving high frequencies because the Ni-doped Sr–Co ferrites with the greatest Ni2+ concentration have the lowest dielectric loss, dielectric constant, and tangent loss value.

The structural, biological and dielectric properties of Sr, Mg and Zn doped silicate ceramics

The current work examines the structural and biological characteristics of doped Zn, Mg, and Sr. Na2O–CaO–Si2O–P2O5 silicate ceramics synthesized by the solid state method. The undoped sample showed amorphous behavior after sintering at the 800 OC while doping of SrO, MgO and ZnO induce crystal growth; and a single phase of Parawollastonite (JCPDS# 00-043-1460) was identified in both doped samples. The strontium doped sample showed the highest value of the dielectric as compared to other three samples. The Sr doped sample had higher dielectric value because the size of Sr2+ is greater than Ca+2 so it will possess the higher polarizing power. Conductivity of Zn and Sr doped samples increased with increase in frequency and Mg doped decrease with increase in frequency. Bioactivity test confirmed that doped samples were more bioactive as compared to undoped samples, and Sr doped sample showed superior bioactivity as compared to other samples.

Structural and dielectric properties of Sr substituted BaTi0.8Zr0.2O3 perovskite synthesized via solid state reaction route

Structural and dielectric properties of Sr substituted BaTi0.8Zr0.2O3 perovskite synthesized via solid state reaction route

2-D Surface Morphology and Dielectric Properties of Sr and Zr co-doped CaTiO3

The ceramic sample of Ca1-xSrxTi1-yZryO3 where x = 0.5 and y = 0.5 (CSTZO) was synthesized by solid state reaction method. Analysis of X-ray diffraction data confirmed the formation of orthorhombic phase. The 2-D surface mo rphology was studied using scanning electron microscopy (SEM). The micrograph shows that the spherical shaped grains vary in the range of 1-2μm and the size of agglo merates varies in the range of 5 to 10 μm in diameter. The dielectric permittivity improved by the substitution of Sr and Zr on A and B-sites. Further, the dc conductivity measured by the two probe method in a temperature scan of 470K to 670K, showed NTCR of the material.

Термооптические и диэлектрические исследования сегнетоэлектрической фазы, индуцированной кальцием, в виртуальном сегнетоэлектрике SrTiO-=SUB=-3-=/SUB=-

AbstractWe have examined temperature changes of the light refraction, birefringence, dielectric permittivity, and dielectric hysteresis loops in Sr_1 – x Ca_ x TiO_3 single crystals with x = 0.014 (SCT-1.4). The dielectric properties of Sr_1 – x Ca_ x TiO_3 with x = 0.007 (SCT-0.7) have been studied. We have performed ab initio calculations of equilibrium structures and total energies for three low-temperature phases of SrTiO_3 and CaTiO_3, based on which we have determined an expected symmetry of the ground state of their solid solution and spontaneous polarization directions in a calcium-induced ferroelectric phase in Sr_1 – x Ca_ x TiO_3. In SCT-1.4, we have separated a spontaneous contribution to the light refraction, which arises due to the spontaneous electrooptical effect caused by the spontaneous polarization and its fluctuations. From the spontaneous contribution to the light refraction, based on a previously developed our phenological approach, we have quantitatively determined for the first time the values and temperature dependences of root-mean-square fluctuations of the order parameter—the polarization P _sh = 〈 P _fl ^2 〉^1/2(short-range, local polar order) in the ferroelectric phase. From optical and dielectric measurements in SCT-1.4, the average value of spontaneous polarization P _ s (the contribution from the long-range order) has been determined. We have estimated the values of P _sh and P _ s , which characterize the short- and long-range orders in the ferroelectric phase of SCT-0.7. Separate determination of the values and temperature dependences of P _ s and P _sh (which considerably exceeds the value of P _ s in the ordered phase) has allowed us to reveal on a quantitative level new particular features of the formation of the induced polar phase in Sr_1 – x Ca_ x TiO_3.

Lattice strain driven dielectric insulation response of Sr1−xCaxBi2Nb2O9 ceramics

In this paper, effects of lattice strain on dielectric properties of Sr[Formula: see text]CaxBi2Nb2O9 ([Formula: see text]–0.5 in steps of 0.1) ceramics are reported. High frequency dipolar polarization is observed to increase for 10% calcium addition and suppresses thereafter on higher calcium concentrations. The dielectric loss values for all doped samples were lower compared to undoped one at frequencies beyond 1[Formula: see text]kHz. The sample with [Formula: see text] shows room temperature dielectric constant in the range (130[Formula: see text][Formula: see text][Formula: see text]12) over a wide frequency range from 50[Formula: see text]Hz to 1[Formula: see text]MHz also minimum dielectric loss among all other sample for the same frequency range. Remarkable increase in Curie temperature ([Formula: see text]) by 50[Formula: see text]C is recorded in the present work by increasing 10% calcium content in SBN compostion. All higher doped samples indicate increase in [Formula: see text] by further higher amount. In addition, dc conductivity of all samples is measured for all samples and increase in calcium content is observed to generate more insulating compositions compared to undoped SBN with higher intrinsic activation energies.

Effect of Sintering Atmosphere on Microstructure and Dielectric Properties of Sr(Fe0.5Nb0.5)O3 Ceramics

The Sr(Fe0.5Nb0.5)O3 (SFN) dense ceramics were sintered at 1450°C in N2, air and O2 atmosphere for 3 h, respectively. All ceramics sintered at various atmospheres exhibited a single phase with perovskite structure in the space group Pmm(221). The microstructure and dielectric properties of SFN ceramics were related to the sintering atmospheres. The dielectric constant of the sample sintered in N2 atmosphere reached the highest value (about 23,000) at room temperature. With the increasing of the oxygen partial pressure, the dielectric constant decreased significantly. Moreover, the complex plane impedance plots even demonstrated that the samples were electrically heterogeneous and consisted of low resistive grains and high resistive grain boundaries. The giant dielectric phenomenon of SFN ceramics was therefore attributed to the IBLC model. The resistivity of grain boundary increased drastically with increasing the oxygen concentration while the resistivity of grain increased inconspicuously. With XPS analysis, it was illustrated that the oxygen vacancy concentrations of SFN ceramics decreased with increasing oxygen concentration, which indicated that a higher value of dielectric constant of SFN ceramics was obtained at lower oxygen concentration. The results strongly indicated that further improvement of the dielectric characteristics in the present ceramics is expected by optimizing sintering atmospheres.

Preparation and dielectric properties of Sr(Fe0.5Nb0.5)O3 by coprecipitation method

A coprecipitation synthesis is applied to prepare Sr(Fe0.5Nb0.5)O3 powders for the first time. Pure perovskite phase Sr(Fe0.5Nb0.5)O3 is obtained at relative low calcination temperature of 950 °C. The powder exhibits a nano-size grain (~40 nm) with a relatively uniform particle size and microstructure. The effect of sintering temperature on microstructure and dielectric properties of SFN ceramics are analyzed. Microstructure analysis shows well-grown and dense microstructure in all samples by two-step sintering. The ceramics of SFN sintered at 1,400 °C with very low dielectric loss (0.08) under 1 kHz frequency at room temperature is obtained. The SFN ceramics exhibit frequency stability over a board frequency interval (100 Hz–100 kHz). The dielectric relaxation is a Debye-like relaxation. The relaxation time (τ) well follows the Arrhenius law and the relaxation is a thermal activated process. The decreased value of activation energy with sintering temperature increasing is related to potential barrier height of electron-hopping.

Effects of barium substitution on the dielectric properties of Sr(Fe0.5Nb0.5)O3 ceramics

The Ba-substituted Sr1−x Ba x (Fe0.5Nb0.5)O3 (SBFN, x = 0, 0.2, 0.5, 0.8) ceramics were prepared by a conventional solid-state sintering, and their microstructure and dielectric properties were investigated. The single-phase SBFN were obtained up to x = 0.8 Ba substitution and the lattice parameter increased with Ba substitution concentration. The dielectric constant increased with Ba substitution, and the highest value of ~180,000 was observed in the x = 0.8 Ba-substituted specimen at 1 kHz. Besides, the dielectric constant increased rapidly a giant value more than 106 over a broad temperature range for x = 0.8 Ba-substituted specimen. The obtained electric and dielectric properties in Ba-substituted SBFN were discussed in terms of the internal barrier layer capacitor model and electrode response.

Synthesis, structural, electrical and dielectric properties of Zn–Zr doped strontium hexaferrite nanoparticles

Zinc-Zirconium doped Strontium hexaferrite SrZnxZrxFe12−2xO19 (where x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) have been successfully synthesized via sol–gel auto combustion technique. The as-synthesized samples were characterized by thermo gravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The X-ray powder diffraction results showed that the sample was single phase with the space group of P63/mmc. The lattice constant ‘a’ almost remains constant while ‘c’ increases as Zn–Zr concentration ‘x’ increases. The crystallite size obtained from XRD data is in the range of 36–47 nm. The average grain size as determined by SEM was found in the range of 40–90 nm. EDS analysis showed that the composition obtained is near stoichiometric. D.C. electrical resistivity measurements were carried out within the temperature range of 300–923 K. It is observed that the resistivity decreases whereas the drift mobility increases as Zn–Zr content ‘x’ increases. The activation energy is found to decrease with the concentration ‘x’. Dielectric measurements were carried out within the frequency range of 50 Hz–5 MHz. It is found that dielectric constant (e′) and dielectric loss tangent (tan δ) both increases as the Zn–Zr concentration ‘x’ increases. Moreover, the structural, morphological, electrical and dielectric properties of Sr–M ferrite powders were strongly depend upon the synthesis condition.

ChemInform Abstract: Characterization and Dielectric Properties of Sr4M2Ti4Ta6O30 (M: Pr and Eu) Ceramics.

AbstractThe title compounds are prepared by solid state reaction of SrCO3, Ln2O3 (Ln: Pr, Eu), TiO2, and Ta2O5 (1450—1500 °C, 4 h) and characterized by XRD, SEM, and dielectric measurements.

Dielectric properties and microstructure of Sr 0.8(K,Na) 0.2Bi 2Nb 2O 9 ferroelectric ceramics

The influence of the microstructure on dielectric properties of Sr 0.8(K,Na) 0.2Bi 2Nb 2O 9 (SKNBNO) prepared by the solid-state route is reported. The formation of Bi-layer structure was obviously restrained owing to the K and Na ions substituting Sr ions by the X-ray diffraction analysis (XRD) and scanning electron micrograph (SEM). At the same time, some slight secondary phase of bismuth oxide was detected but the structure was not changed. The dielectric constant was restrained by K and Na ions substituting Sr ions, which is mainly attributed to the slight change of lattice constants resulting in a decreased “rattling space” for the cations inside the distorted Nb(V)O 6 oxygen octahedron of the perovskite block. A clear enhancement in the stability of frequency and temperature was noticed for SKNBNO sample compared to Sr 2Bi 2Nb 2O 9 (SBN) samples.

Preparation and dielectric properties of Sr(Ti 0.95Zr 0.05)O 3 ceramics doped with CaO [sbnd]TiO 2[sbnd]SiO 2 (CTS)

Sr(Ti 0.95Zr 0.05)O 3 ceramic was sintered using x mol.% CTS ( x = 0, 0.5, 1.5, 4, 7) as sintering additive for the first time. Although Sr(Ti 0.95Zr 0.05)O 3 ceramic could not be fully sintered even at 1420 °C, the densification temperature could be decreased to 1280 °C by using CTS, which begin melting when temperature reaches higher than 1150 °C. The microstructures of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Apparent density and the dielectric properties were established at room temperature. The measuring frequency was 1 MHz. The microstructure and dielectric properties greatly changed depending on the amount of CTS additive. The optimum concentration to obtain nicer dielectric properties was 0.5 mol.%.

Dielectric properties of Sr 0.8Bi 2.2(V 0.2Nb 0.8) 2O 9 ceramic

Results of systematic studies on dielectric properties of Sr 0.8Bi 2.2(V 0.2Nb 0.8) 2O 9 prepared by solid state route is reported. A clear enhancement in the peak dielectric constant at the Curie temperature was noticed for Sr 0.8Bi 2.2(V 0.2Nb 0.8) 2O 9 compared to SrBi 2Nb 2O 9. Scanning electron micrograph (SEM) of Sr 0.8Bi 2.2(V 0.2Nb 0.8) 2O 9 revealed dense structure by vanadium doping, although small voids or pores were found in the sample.

Dielectric properties of Sr 1− XBi 2+(2/3) X(V XNb 1− X) 2O 9 [ X = 0.1 and 0.2] ceramics

The results of systematic studies on the dielectric properties of Sr 1− X Bi 2+(2/3) X (V X Nb 1− X ) 2O 9 [ X = 0.1 and 0.2] ferroelectric ceramics are reported. X-ray diffraction (XRD) studies on Sr 1− X Bi 2+(2/3) X (V X Nb 1− X ) 2O 9 with X = 0.1 revealed that the single-phase layered perovskites was formed without any detectable secondary phase. However, with X = 0.2 in addition to the major layered perovskite phase, a minor unknown phase was noticed. An enhancement in the dielectric properties of SrBi 2Nb 2O 9 (SBN) was observed with the increase in partial substitution of pentavalent niobium ions (0.68 Å) by smaller pentavalent vanadium ions (0.59 Å) in the B sites along with the deficiency of strontium ions in the A site.

Dielectric properties of Sr 1+XBi 2−(2/3)X(V XTa 1−X) 2O 9 [ [formula omitted], 0.1 and 0.2] ceramics

In this paper, we report the results of systematic studies on the dielectric properties of Sr 1+ X Bi 2−(2/3) X (V X Ta 1− X ) 2O 9 [ X = 0 , 0.1 and 0.2] ferroelectric ceramics. The X-ray diffraction results confirm that single-phase layered perovskites were formed within the composition range studied in this work without any detectable secondary phase. Higher Curie temperature and enhanced dielectric constant at the transition temperature were clearly observed with the partial substitution of pentavalent tanatalum ions by smaller pentavalent vanadium ions. The negative shift of Curie temperature with increasing frequency was observed for Sr 1+ X Bi 2−(2/3) X (V X Ta 1− X ) 2O 9 [ X = 0.1 and 0.2] ceramics.

Sintering and dielectric properties of Sr(Bi2Ta2)1−xTi4xO9 ceramics

Abstract The influence of Ti 4+ substitution on the dielectric properties of Sr(Bi 2 Ta 2 ) 1− x Ti 4 x O 9 (SBTT) ceramics ( x up to 0.2) has been studied. The sintering temperature of SBTT slightly decreases as the TiO 2 content increases with the partial substitution of Bi 2 O 3 and Ta 2 O 5 by TiO 2 . X-ray diffraction analysis on SBTT ceramics with low TiO 2 content and sintered at lower temperature indicate that single-phase layered perovskite ferroelectrics are obtained and no TiO 2 phase is found, while the TiO 2 crystal phase increases with the TiO 2 content and sintering temperature. The incorporation of Ti 4+ into SrBi 2 Ta 2 O 9 results in a shift of the Curie temperature to higher values than for SrBi 2 Ta 2 O 9 . Nevertheless, the Curie temperature is not a function of sintering temperature and TiO 2 content.

Dielectric properties and phase transition mechanisms in Sr 1−xBa xTiO 3 solid solution at low doping concentration

Dielectric properties of Sr 1− x Ba x TiO 3 ( x ≦ 0.30) solid solution were studied by means of dielectric constant, DE loop, pyroelectricity measurements, and so on. A quantum paraelectric to quantum ferroelectric transition was observed for samples with a small amount of Ba content ( 0.005 ≦ x ≦ 0.10). Possible phase transition mechanisms are discussed.

Effect of poling process on the piezoelectric and dielectric properties of Nb and Sr-doped PZT ceramics

The piezoelectric and dielectric properties of Sr and Nb doped lead zirconate titante (PZT) used for electroacoustic transducers have been investigated as a function of the poling field and poling time. The optimum poling conditions were determined from the measurement of maxima of the radial planar coupling factor (kp) and the relative dielectric constant (εr) at various poling parameters. The data showed that the mentioned quantities reach the maximum values and then saturate at an external electric field up to the saturation field in a suitable time. Large external fields associated with the extension of poling time above the optimal values produced the degradation of investigated electromechanical coefficient and the dielectric constant.