Microwave Dielectric Properties Of Ca Research Articles

Effect of Ba addition on the dielectric properties and microstructure of (Ca0.6Sr0.4)ZrO3

This study focuses on the synthesis and characterization of Ca0.6Sr0.4-xBaxZrO3 (x = 0.01, 0.04, 0.07, and 0.10) ceramics prepared via the solid-state method and sintered at 1450 °C. The impact of Sr substitution by Ba at the A-site of the perovskite structure on crystalline properties and microwave dielectric performance was investigated. The experimental results show the formation of a single-phase structure, Ca0.612Sr0.388ZrO3(CSZ), across the entire range of x values. It is evident that the Ca0.6Sr0.39Ba0.01ZrO3 ceramics exhibits the highest sintering density and the lowest porosity. These ceramics exhibit impressive dielectric properties, including a high permittivity of 28.38, low dielectric loss of 4.0×10−4, and a Q factor value of 22988 at 9–10 GHz. The research reveals that the influences of Sr substitution by Ba in enhancing the microwave dielectric properties of Ca0.612Sr0.388ZrO3 ceramics, and the impedance curves clearly showed effects on the electrical properties.

Effect of B-site complex substitutions on orthorhombic distortion and microwave dielectric properties of Ca(Zr0.95Ti0.05)O3 perovskites

The effects of complex-ion (Zn1/3Nb2/3)4+ substitutions on the crystal structure, microstructure and microwave dielectric properties of Ca(Zr0.95Ti0.05)O3 were shown.

Effect of crystal structure of Ca2AMg2Ge2VO12 (A = Y, Eu) garnets on microwave dielectric properties

The optimal microwave dielectric properties of Ca 2 AMg 2 Ge 2 VO 12 (A = Y, Eu) garnets are reached at the sintering temperature of 1300 °C for 6 h ( ε r = 10.1, Q × f = 65,600 GHz and τ f = −53 ppm/℃ for Ca 2 YMg 2 Ge 2 VO 12 ; ε r = 9.4, Q × f = 37,900 GHz and τ f = −55 ppm/℃ for Ca 2 EuMg 2 Ge 2 VO 12 ). The dielectric loss of Ca 2 AMg 2 Ge 2 VO 12 (A = Y, Eu) has been measured at a frequency of 13 GHz, and the dielectric loss of these ceramics is mainly affected by the pore volume and atomic packing fraction. The Ca-O and Mg-O bonds are compressed, while the Y-O, Eu,-O, Ge-O, and V-O bonds are in an expanded state. The higher ε r (C-M) calculated by the Clausius-Mossotti (C-M) equation than the measured ε r is attributed to the compression state of 24c-site (Ca 2 /A). The negative τ f value of Ca 2 AMg 2 Ge 2 VO 12 is derived from the positive τ αm value greater than 3 α L . And the slight difference in τ f of Ca 2 YMg 2 Ge 2 VO 12 and Ca 2 EuMg 2 Ge 2 VO 12 is also slightly compressed at the Ca/A-site.

Phase composition and microwave dielectric properties of Ca0.128Ba0.032Sm0.46Li0.3TiO3 ceramics with alumina addition

Ca0.128Ba0.032Sm0.46Li0.3TiO3-x wt.% Al2O3 microwave dielectric ceramics with temperature stability were prepared by the traditional solid-state reaction method. The effects of Al2O3 doping on phase composition, micromorphology, and microwave dielectric properties of Ca0.128Ba0.032Sm0.46Li0.3TiO3 ceramics were investigated. X-ray diffraction results showed that no other phase was introduced by doping, and the diffraction peaks of all the ceramics could be indexed by standard JCPDS cards of No.42−0423 (CaTiO3) and No.43−0235 (BaSm2Ti4O12). To further study the effects of Al2O3 doping on microstructure and lattice vibration of Ca0.128Ba0.032Sm0.46Li0.3TiO3 ceramics, the structural refinement and Raman spectroscopy techniques were also adopted. Doping Al2O3 decreased the lattice constant of CaTiO3-phase solid solution, modified the morphology and improved microwave dielectric properties of the ceramics. When sintered at 1300 °C for 4 h, the ceramics with 0.9 wt.% Al2O3 showed excellent microwave dielectric properties: εr = 87.9 ± 0.4, Q × f = 6671 ± 103 GHz, and τf = -1.2 ± 0.9 ppm/℃.

Highly enhanced Q × f value of Ca0.61Nd0.26TiO3 ceramics with SnO2 additive

The microstructure and microwave dielectric properties of Ca0.61Nd0.26TiO3 + x mol SnO2 (0 ≤ x ≤ 0.05) ceramics (CNTSx) were investigated by Field Emission Scanning Electron Microscope, Hakki-Coleman dielectric resonator, network analyser and X-ray Diffractometer. The XRD results indicated that all CNTSx samples were formed as orthorhombic-perovskite-structured CaTiO3 phase. There were second phase Ti0.7Sn0.3O2 in range of 0.02 ≤ x ≤ 0.05. The SnO2 additive promoted the grain size of CNT ceramic, which was conducive to the promotion of Q × f value. Although the ϵr value declined as contents of SnO2 increased, the SnO2 additive had a little of amelioration for τf value. Finally, the CNTS0.01 ceramic sintered at 1400 °C had stable comprehensive dielectric characteristic: ϵr ∼ 105.2, Q × f ∼ 14,369 GHz, τf ∼ +262.3 ppm/ºC.

Sintering behavior, microwave dielectric properties of Ca0.66Ti0.66Nd0.34Al0.34O3 ceramics revealed by microstructure and Raman scattering

Ca0.66Ti0.66Nd0.34Al0.34O3(CTNA) ceramics were prepared by solid-state reaction method and their sintering behavior, microwave dielectric properties, and microstructure were investigated. CTNA ceramics were examined by Raman scattering to reveal the correlation of perovskite structure with the microwave properties. It found that the area of peak A1g(O) stretch mode reflects the quality factor Q × f value in the perovskite materials. This concludes that the oxygen octahedron plays an important role of the material's microwave performance. Sintering temperature affected the unit cell volume and the lattice parameters of the CTNA ceramics, the grain size distribution, the Gibbs free energy, the thermal expansion coefficient (CTE), and the dielectric properties (εr, Q×f, τf). The samples sintered at 1500 °C displayed the best dielectric constant and Q×f, as 44.94 and 41922.22 GHz, respectively.

Effects of (Cr0.5Ta0.5)4+ on structure and microwave dielectric properties of Ca0.61Nd0.26TiO3 ceramics

The Ca0.61Nd0.26Ti1-x(Cr0.5Ta0.5)xO3 (CNT-CTx) ceramics with orthorhombic perovskite structure were prepared using the conventional solid-state method. The X-ray diffraction (XRD), Raman spectra and X-ray photoelectron spectra (XPS) were employed to investigate the correlations between crystal structure and microwave dielectric properties of CNT-CTx ceramics. The XRD results showed that all CNT-CTx samples were crystallized into the orthorhombic perovskite structure. The SEM micrographs indicated that the average grain size of samples depended on the sintering temperature. As (Cr0.5Ta0.5)4+ concentration increased, there was a significant decrease in the average grain size of samples. The short range order (SRO) structure and structural distortion of oxygen octahedra proved to exist in CNT-CTx crystals according to the analysis of Raman spectra results. The microwave dielectric properties highly depended on the full width at half maximum (FWHM) of Raman spectra, oxygen octahedra distortion, reduction of Ti4+ to Ti3+ and bond valence. At last, the CNT-CT0.05 ceramic sintered at 1420 °C for 4 h exhibited the good and stable comprehensive microwave dielectric properties: relative permittivity of 96.5, quality factor of 14,360 GHz, and temperature coefficient of resonant frequency of +153.3 ppm/°C.

Crystal structure and microwave dielectric properties of Ca[(1/3Nb2/3)0.92Zr0.08]O3−δ-xTiO2ceramics

The effects of B2O3on the sinterability and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.92Zr0.08]O3−δ ceramics were investigated. B2O3doping can effectively reduce sintering temperatue by 150~200°C. The temperature coefficient of resonator frequency τf increased with an increase of B3O3content and sintering temperatue. When B2O3of 2wt% were added, the optimum microwave dielectric properties: εr=28.5,Qf =13560GHz and τf= − 7.6×10–6/°C were obtained at the sintering temperature of 950°C.

Effect of A-Site Non-stoichiometry on Structure and Microwave Dielectric Properties of Ca x (Li0.36Nd0.36Bi0.14Na0.14)TiO3 Ceramics

By adding a small amount of calcium to the starting composition, Li0.36Nd0.36Bi0.14Na0.14TiO3, oxygen vacancies are suppressed and, therefore, the microwave properties are enhanced. This study not only obtained a kind of ceramic with excellent microwave dielectric properties, e r ∼ 160, Q × f ∼ 1300 GHz and τ f ∼ 10 ppm/°C, but also gives a way to optimize the compositions with various donor and acceptor dopants for better performance in microwave ceramics.

Preparation and microwave dielectric properties of Ca 0.6 La 0.8/3 (Sn x Ti 1−x )O 3 ceramics

Abstract Ca 0.6 La 0.8/3 (Sn x Ti 1−x )O 3 ceramics were prepared via a conventional solid state reaction method, and the effect of Sn doping on their crystal phase structure and microwave dielectric properties was investigated. Results showed that Sn doping could hinder the formation of the rutile TiO 2 detrimental phase of Ca 0.6 La 0.8/3 TiO 3 ceramic. Also, the Q×f 0 value was enhanced and the τ f value was lowered by Sn doping. The best microwave dielectric properties, i. e. e r =113 and Q×f 0 =8487 GHz were obtained for a Sn doping content of 0.02. The mechanism of the improved properties deriving by Sn doping is discussed.

Impacts of Al2O3 Doping on Microstructure, Phase Constitution and Microwave Dielectric Properties of Ca0.61Nd0.26TiO3 Ceramics

The effects of Al2O3 addition on microstructure, phase evolution and microwave dielectric properties of Ca0.61Nd0.26TiO3 – x mol Al2O3 (x = 0, 0.025, 0.05, 0.075, 0.1) ceramics have been investigated in this study. With x increasing from 0 to 0.05, the system maintained a single perovskite phase while bulk density decreased rapidly due to grain size degradation. Correspondingly, dielectric constant (ϵr) decreased from 103 to 79.2 and temperature coefficient of resonant frequency (τf) dropped from +247 to +159.3 ppm/°C. Moreover, anti-reduction of Ti4+ gave rise to a nearly doubled Q×f value, from 8600 to 15500 GHz. For 0.075≤x≤0.1, X-ray diffraction results showed a secondary phase whose peaks were consistent with Ca2Nb2O7 phase, resulting in decreased microwave dielectric properties.

Zn-B-O 글라스 첨가에 의한 Ca[(Li1/3Nb2/3)0.2Ti0.8]O3-δ세라믹스의 마이크로파 유전특성

Zn-B-O 글라스 첨가에 의한 Ca[(Li_1/3Nb_2/3)_0.2Ti_0.8]O_3-_δ세라믹스의 마이크로파 유전특성

Improving microwave dielectric properties of Ca0.6La0.8/3(Sn0.02Ti0.98)O3 ceramics by CeO2 addition

The effect of CeO2 addition on the preparation and microwave dielectric property of Ca0.6La0.8/3(Sn0.02Ti0.98)O3 ceramics was investigated. Results showed that the microstructure and bulk density were effectively improved and the dielectric loss was lowered for the samples added with CeO2, which were responsible for the increase in Q×f0 value. The as-prepared sample with 0.2wt% CeO2 exhibited the better microwave dielectric properties, i.e. εr ~116 and Q×f0 ~11,176GHz. The mechanism of the properties improved by adding CeO2 was discussed.

Microwave property improvement of Ca[(Li1/3Nb2/3)0.95Zr0.15]O3+δ perovskite by A-site substitution

The crystal structure and microwave dielectric properties of Ca[(Li[Formula: see text]Nb[Formula: see text])[Formula: see text]Zr[Formula: see text]]O[Formula: see text] ceramic (CLNZ) are tuned by A-site substitution of Sr[Formula: see text] and Ba[Formula: see text] ions in the present paper. The tuning effect on the crystal structure is investigated by the X-ray diffraction (XRD) pattern and it illustrates that single phase of orthorhombic perovskite structure is formed, however, minor amount of BaNb2O6-type second phase is also detected in (Ca[Formula: see text]Ba[Formula: see text])[(Li[Formula: see text]Nb[Formula: see text])[Formula: see text]Zr[Formula: see text]]O[Formula: see text] ceramics (CBLNZ) in the range of [Formula: see text], while pure perovskite phase is obtained in (Ca[Formula: see text]Sr[Formula: see text][(Li[Formula: see text]Nb[Formula: see text])[Formula: see text]Zr[Formula: see text]]O[Formula: see text] ceramics (CSLNZ) in the whole investigation range of [Formula: see text]. With the increase of [Formula: see text] value, the unit cell volumes of both CBLNZ and CSLNZ perovskites gradually expand, which results in the degradation of the vibration bond strength between the B-site ions and oxygen in the perovskites. The microscopic structure related thermal parameters in CSLNZ and CBLNZ perovskites are analyzed in terms of Clausius–Mossotti equation to reveal the original contributors in the temperature coefficients. The results show that both Sr[Formula: see text] and Ba[Formula: see text] substitution can effectively improve the permittivity and [Formula: see text] value, especially, improve the temperature coefficient of CLNZ ceramic in a certain range.

Effect of SiO2 Addition on Microwave Dielectric Properties of Ca0.61La0.39Al0.39Ti0.61O3 Ceramics

Effect of SiO2 Addition on Microwave Dielectric Properties of Ca0.61La0.39Al0.39Ti0.61O3 Ceramics

Influence of La–B–Zn glass on the sintering and microwave dielectric properties of Ca–Nd–Ti ceramics

The effects of La2O3–B2O3–ZnO (LBZ) glass on the sintering behaviors, phase structures, microstructures and the microwave dielectric properties of perovskite type Ca0.6Nd0.26TiO3 (CNT) ceramics were studied. It indicates that the LBZ glass has an obvious effect on lowering the sintering temperature without damaging the microwave dielectric properties of the CNT ceramics. Small amounts of LBZ glass significantly lowered the sintering temperatures of CNT ceramics and obtained excellent microwave dielectric properties. However, too much LBZ glass is leading to inferior dielectric properties. The CNT ceramics doped with 3 wt% LBZ can be well sintered at 975 °C for 4 h and shows good properties: er = 87.87, Q × f = 8132 GHz (f = 3.3 GHz), τf = +244.63 ppm/°C.

Structure and microwave dielectric properties of Ca0.66La0.387Ti0.88O3 ceramics

Ca0.66La0.387Ti0.88O3 microwave dielectric ceramics were prepared via a mixed oxide solid state sintering route and characterized. X-ray diffraction revealed the formation of single phase Ca0.66La0.387Ti0.88O3 ceramics with orthorhombic (Pbnm) symmetry within the detection limit of the in-house XRD facility. Raman spectroscopy revealed the presence of seven Raman active bands evident of orthorhombic symmetry, in agreement with the present X-ray diffraction results. The microstructure of sintered samples appeared almost dense with some occasional pores. Ca0.66La0.387Ti0.88O3 exhibited reasonable relative permittivity (~71.5) and quality factor (~13,407 GHz); however, its temperature coefficient of resonance frequency was high (~136.4 × 10−6/°C) for commercial applications and requires further optimization.

Low-temperature sintering and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]3−δ with glass frit added

In accordance with the trend for mobile terminals to be high intensity and to have thinner layers, low temperature co-fired ceramics (LTCC) materials with outstanding dielectric loss characteristics and diverse dielectric constants have been in demand, and the need for high-strength materials that can withstand external shocks has increased. Ca[(Li1/3Nb2/3)1−x Ti x ]O3−δ (CLNT) has a quality factor over 14,000 and τ f ≤ 10 when the dielectric constant is 41 ∼ 46, but its sintering temperature is high at 1150 °C. Therefore, it cannot be used as a LTCC component. This study aimed to lower the sintering temperature to 900 °C by adding a low-melting-point glass such as B2O3·SiO2·BaO and B2O3·SiO2·Al2O3. As the glass content in CLNT was increased from 10 wt% to 20 wt%, the density and the Q·f0 property decreased, and the dielectric constant rose. When B2O3·SiO2·BaO was added to CLNT at 15 wt%, the dielectric constant was found to be 27, the Q·f0 property to be 3470, and the τ f to be −18 ppm/°C. When B2O3·SiO2·Al2O3 was added to CLNT at 10 wt%, the dielectric constant was 20, the Q·f0 property was 3990, and the τ f was −15 ppm/°C. As such, in both cases, excellent dielectric properties were observed.

Effect of TiO2 and CaTiO3 additives on the sintering behavior and microwave dielectric properties of Ca(Mg0.92Al0.08)(Si0.96Al0.04)2O6 ceramics

Ca(Mg0.92Al0.08)(Si0.96Al0.04)2O6 ceramics with different amounts of TiO2/CaTiO3 additions were prepared by the solid-state reaction method. The sintering behavior, microstructure and microwave dielectric properties of TiO2/CaTiO3-added ceramics were investigated. The control of the temperature coefficient of resonant frequency (τf) could be achieved by varying the content of TiO2 or CaTiO3. Particularly, TiO2 reacted with the main ceramic phase of Ca(Mg,Al)(Si,Al)2O6 and produced secondary phases of MgTi2O5 and CaTiSiO4O, which lowered the Q×f values of the ceramics. TiO2-added ceramics sintered at 1225°C with 22wt% TiO2 additions showed dielectric properties of εr=12.06, Q×f=5940GHz and τf=2.24ppm/oC. Comparing with the TiO2-added ceramics, CaTiO3 just existed as a separate component, and the Ca(Mg0.92Al0.08)(Si0.96Al0.04)2O6 ceramic sintered at 1250°C with 10wt% CaTiO3 additions showed a good combination of dielectric properties: εr=9.6, Q×f=32,590GHz and τf=−1.53ppm/oC.

Microwave Dielectric Properties of Ca[(Li<sub>1/3</sub>Nb<sub>2/3</sub>)<sub>0.92</sub>Zr<sub>0.08</sub>]O<sub>3</sub><sub>−δ </sub>Ceramics with Glass Addition

The effects of ZnO-B2O3-Na2O(ZBN) glass on the sinterability and microwave dielectric properties of Ca [(Li1/3Nb2/3)0.92Zr0.08]O3−δ −0.05TiO2 ceramics were investigated . ZBN glass doping can effectively reduce sintering temperatue by 100~150oC. The temperature coefficient of resonator frequency τf increased with an increase of ZBN glass content and sintering temperatue. When ZBN glass of 1.8wt% were added, the optimum microwave dielectric properties: εr=32.8, Qf =13420GHz and τf= − 4.3×10−6/oC were obtained at the sintering temperature of 1000oC.