Microwave Dielectric Properties Of Er Research Articles

The Effect of Y3+ Doping on CaTiO3-LaAlO3 Microwave Dielectric Ceramics

CaTiO3-LaAlO3 solid solution with perovskite structure has suitable relative permittivity (εr) and high quality factor (Q×f) for application as dielectric resonators, but the negative value of the temperature coefficient of resonance frequency (τf) affects its utilization. To improve dielectric properties and adjust lattice matching, Y3+ ion was selected as doping element to prepare the 0.65CaTiO3-0.35(La1-xYx)AlO3 (x=0, 0.02, 0.04, 0.06, 0.08 ) microwave dielectric ceramics by conventional mixed solid method. The effects of Y3+ ion doping on the crystal structure and microwave dielectric properties were investigated. The results revealed that a single orthorhombic phase for all the compositions can form and the unit cell volume increases linearly with the doping content x. Y3+ ion dopant can increase the quality factor and improve the temperature coefficient of resonant frequency of 0.65CaTiO3-0.35LaAlO3 ceramics. When x = 0.02, the optimal microwave dielectric properties of εr=45.8, Q×f = 38957 GHz, and τf = 4×10−6/oC for the 0.65CaTiO3-0.35(La1-xYx)AlO3 ceramics could be obtained, which sintered at 1500 °C for 5 h.

Low temperature sintering mechanism for Li2Mg3SnO6 microwave dielectric ceramics

Low-fired Li2Mg3SnO6 ceramics were fabricated via the conventional solid-state reaction route, and the effects of LiF-doping on their sintering mechanism and microwave dielectric properties were investigated. Sintering temperature of Li2Mg3SnO6 ceramics were effectively reduced to 900 °C due to the substitution of F− for O2−, which could cause weakening of oxygen bond strength induced reduced the intrinsic sintering temperature and facilitates the diffusion process. Low-fired ceramics inhibited volatilization of Li and improved relative density. Well-densified Li2Mg3SnO6-4 wt% LiF ceramics were obtained with optimum microwave dielectric properties of εr = 12.3, Q × f = 96280 GHz and τf = −40.7 ppm/°C at 900 °C. Such samples were compatible with Ag electrodes and suitable for LTCC applications.

Phase compositions, microstructures, and microwave dielectric properties of Li2Zn3Ti4O12-based temperature stable materials modified by CaTiO3 additions

In present work, the microwave dielectric properties of CaTiO3-added Li2Zn3Ti4O12 ceramics prepared by the conventional solid-state method have been investigated. The phase composition, microstructure and microwave dielectric properties of (1 − x) Li2Zn3Ti4O12–x CaTiO3 (x = 3, 4, 5, 6 and 7 wt%) ceramics were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), EDS and network analyzer. The XRD and EDS results indicated that the ceramics involved Li2Zn3Ti4O12 and CaTiO3 phases. The SEM micrographs shown that as the CaTiO3 contents increased, the average grain size of the composition ceramics decreased. The microwave dielectric properties of the composition ceramics can be effectively controlled by varying the CaTiO3 contents. The values of dielectric constant (er) and τf of the composition ceramics were increased, and the quality factor (Q × f) was decreased with increasing the CaTiO3 contents. Typically, a new temperature stable microwave dielectric material of 0.94 Li2Zn3Ti4O12–0.06 CaTiO3 with excellent microwave dielectric properties of er = 21.7, Q × f = 61,490 GHz, and τf = + 2.68 ppm/°C was attained when sintered at 1175 °C for 4 h.

Crystal structure, Raman spectra analysis and microwave dielectric properties optimization of (Ca0.22Li0.39Sm0.39)TiO3 ceramics doped with SmAlO3

(Ca0.22Li0.39Sm0.39)TiO3 + x mol SmAlO3 (0, 0.02, 0.04, 0.06, 0.08, 0.1) (CLST + xSA) ceramics were synthesized by a solid-state reaction method. CLST + xSA solid solution ceramics with an orthorhombic perovskite structure (pnma (62) (42–0423)) were obtained and verified by X-ray diffraction (XRD). Structural refinement and Raman spectra were used to investigate the effect of SmAlO3 doping on the microstructure and lattice vibration of CLST ceramics. The Q × f value showed a significant increase from 4754.9 to 6207.5 GHz with increasing SA doping content. The permittivity εr decreased from 109 to 87.4, and the temperature coefficient of resonant frequency τƒ decreased from 7.38 to −20.76 ppm °C−1. The optimal microwave dielectric properties of εr = 98.7, Q × f = 5667.7 GHz and τf = −1.5 ppm °C−1 were obtained in CLST + xSA (x = 0.04) ceramics sintered at 1260 °C.

A novel temperature-stable Ba2-xCaxMgTi5O13 microwave dielectric ceramic

The Ba2-xCaxMgTi5O13 (0 ≤ x ≤ 0.3) microwave dielectric ceramics were for the first time prepared via a conventional solid-state reaction method. A small amount of Ca2+ can dissolve into the lattice by forming solid solutions with a monoclinic structure (C2/m) and further influence the sintering behavior, grain growth and microwave dielectric properties of Ba2-xCaxMgTi5O13 ceramics. Both increase of εr and decrease of Qxf with x should be associated with increased lattice distortion and uneven grain growth although the sample density and the ratio of the ionic polarizability to the molar volume show little variation. Moreover, the A-site bond valence and τf indicate a close relation in current study, such that the Ca2+substitution can induce an increase of τf values. The optimum microwave dielectric properties of εr ∼ 29.3, Qxf ∼ 30,870 GHz (6.5 GHz), and a near-zero τf ∼ +2.1 ppm/°C can be contained in the x = 0.15 ceramic sintered at 1160 °C.

Ultra‐low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi2O6‐based LTCC

AbstractA total of 14 fluoride composite ceramics were prepared through solid‐state method and their microwave dielectric properties were investigated. Among the fluoride composite ceramics, 0.36LiF–0.39MgF2–0.25SrF2 (LMS) had the lowest sintering temperature (600°C) and presented a dielectric constant (εr) of 6.24 ± 0.05, a quality factor (Q × f) of 33 274 ± 900 GHz, and a temperature coefficient resonant frequency (τf) of −86.74 ± 8 ppm/°C. As the LMS ceramic had a low melting point (646°C), it can be used as sintering aid for LTCC applications. The sintering temperature of BaCuSi2O6 decreased from 1050°C to 875°C with 2 wt% LMS doped and excellent microwave dielectric properties of εr = 8.16 ± 0.04, Q × f = 24 351 ± 300 GHz, and τf = −9.74 ± 1 ppm/°C were obtained. Moreover, BaCuSi2O6‐2 wt% LMS can be co‐fired with Ag powders, which makes it a potential new candidate for LTCC applications.

Bismuth borate composite microwave ceramics synthesised by different ratios of H3BO3 for ULTCC technology

Bi3B5+xO12+3x/2 (x = 0∼6) compounds were fabricated by a conventional solid-state reaction method. The microwave dielectric properties, sintering behaviour, crystal structure, and phase evolution of the ceramics were investigated. All samples densified at ultra-low temperatures (575∼700 °C). As x increased, the phase composition of the ceramics gradually changed from mixed Bi4B2O9 and Bi3B5O12 phases to a single Bi6B10O24 phase. The ceramic with x = 4 exhibited the best microwave dielectric properties of εr = 12.14, Q × f = 14,800 GHz, and τƒ = −72 ppm/°C at 625 °C. The microwave dielectric properties deteriorated as x increased further. Moreover, the ceramics were proven to cofire with Al and Ag, indicating that they are candidates for ultra-low-temperature cofired ceramic devices.

A novel low‐permittivity LiAl0.98(Zn0.5Si0.5)0.02O2‐based microwave dielectric ceramics for LTCC application

AbstractPhase composition, morphology, and microwave dielectric properties of (1−x) LiAl0.98(Zn0.5Si0.5)0.02O2 + x CaTiO3 (0.05 ≤ x ≤ 0.20) materials synthesized via the solid state reaction method were investigated. All these densified materials were obtained at a sintering temperature of 1150°C. All compositions showed a major LiAlO2 phase that was accompanied by a minor CaTiO3 phase. The εr value increased gradually from 10.88 to 11.60, whereas the Q × f value remarkably decreased from 33 251 GHz to 13 511 GHz. The τf value changes from −85 ppm/°C to 212 ppm/°C, thereby indicating that CaTiO3 could effectively adjust this value. HBO3‐doping was used to further decrease the sintering temperature to 900°C. The optimum value was obtained at 7 wt.% HBO3 doped with microwave dielectric properties of εr = 9.39, Q × f = 10 224 GHz, and τf = −7.8 ppm/°C. This material also exhibited chemical compatibility with silver, making it a candidate for low temperature co‐fired ceramics applications.

Low-fired Li2Mg3ZrO6-based composite ceramics with temperature-stable for LTCC applications

Low-fired (1-x)Li2Mg3ZrO6-xCaTiO3-4wt%LiF composite ceramics were fabricated by conventional solid-state reaction route. Specimens exhibited a multiphase system with Li2Mg3ZrO6, CaZrO3 and ZrO2 phase and well-dense microstructures at 900 °C. Excellent microwave dielectric properties of εr = 15.4, Q × f = 42400 GHz, τf = −5.6 ppm/°C was obtained for 0.8Li2Mg3ZrO6-0.2CaTiO3-4wt%LiF ceramics. Such samples were compatible with Ag electrodes, which suggests suitability of the developed material for LTCC applications.

A novel Ce2Zr3(MoO4)9 microwave dielectric ceramic with ultra-low firing temperature

A new type of Ce2Zr3(MoO4)9 (CZM) ceramic was successfully prepared through the solid-phase reaction process at low sintering temperature. All the studied sintered samples exhibited a trigonal phase with space group of R-3c (No.167) by means of X-ray diffraction. Rietveld refinement analysis results further explored the crystalline structure of CZM. According to Scanning electron microscopy images, dense uniform surface morphology was observed at 525–625 °C for CZM ceramics. The correlations between structural characteristics and microwave dielectric properties of CZM ceramics were systematically investigated by calculating some chemical bond parameters on the basis of the chemical bonds theory of complex crystals. The analysis results of far-infrared reflectivity spectroscopy revealed that the absorption of structural phonon vibration at infrared frequencies played a dominant role in dielectric polarization contribution for CZM ceramics. Furthermore, the CZM sample sintered at 575 °C exhibited optimum microwave dielectric properties of εr = 10.69, Q·f = 19,062 GHz and τf = −1.29 ppm/°C.

Low temperature sintering and microwave dielectric properties of Nd[(Zn0.7Co0.3)0.5Ti0.5]O3 ceramics derived from the powders synthesized by ethylenediaminetetraacetic acid precursor route

In this work, Nd[(Zn0.7Co0.3)0.5Ti0.5]O3 (NZCT) powders with high reactivity were synthesized by the ethylenediaminetetraacetic acid (EDTA) precursor method in which EDTA acted as a chelating agent. Single-phase NZCT and dense ceramic with about 98.2% of theoretical density were readily developed via sintering the fine powders at 1250 °C for 3 h. X-ray diffraction (XRD) analysis confirmed the formation of single-phase NZCT at 700 °C for 2 h without any intermediate phase. Transmission electron microscopy (TEM) micrograph showed nanocrystalline particles in the range 30–70 nm. The sintered Nd[(Zn0.7Co0.3)0.5Ti0.5]O3 ceramics at 1250 °C for 3 h exhibited uniform microstructure and excellent microwave dielectric properties of εr = 35.66, Q × f = 254200 GHz and τf = −28.3 ppm/oC, indicating that the present developed ceramics might be promising materials for modern communication techniques.

Raman, complex chemical bond and structural studies of novel CaMg1-x(Mn1/2Zn1/2)xSi2O6 (x=0-0.1) ceramics

Low permittivity CaMg1-x(Mn1/2Zn1/2)xSi2O6 (x = 0-0.1) ceramics were synthesized via the solid-state reaction process for the first time. The Rietveld refinement, complex chemical bond theory and Raman spectra were introduced to analyze the effects of Mn2+/Zn2+ co-substitution to microwave dielectric properties. XRD spectra indicate the CaMg1-x(Mn1/2Zn1/2)xSi2O6 ceramics processed the pure phase of CaMgSi2O6 when x ≤ 0.02 and a small volume of secondary phase Ca2MgSi2O7 for 0.04 ≤ x ≤ 0.1. The variation of εr can be put down to average bond iconicity and Raman shift. Total lattice energy and packing fraction are main influence factor of the Q×f value. The monotonous decrease of τf is associated with total bond valence and full width at half maximum of Raman peak. Additionally, CaMg1-x(Mn1/2Zn1/2)xSi2O6 (x = 0.02) ceramics sintered at 1280 °C for 3 h exhibited excellent microwave dielectric properties of εr = 8.16, Q×f = 70187, τf = −38.48 ppm/°C.

Magnesium fluoride doped MgTiO3 ceramics with ultra-high Q value at microwave frequencies

Microwave ceramic with ultra-high Q value is one of the most significant classes of material to realize the miniaturization and integration of microwave devices. In this paper, to improve the microwave dielectric properties of ceramics, MgTiO3-x wt.% MgF2 (x = 0, 3, 4, 5, and 6) microwave ceramics with high-quality factor were synthesized by solid-state reaction method. The effects of MgF2 addition on the phase composition, sintering behavior, and microwave dielectric properties of MgTiO3 were investigated. In comparison to pure MgTiO3, our study demonstrates that the Q × f values can be dramatically enhanced with the doping of MgF2. After being sintered at 1300 °C for 4 h, the MgTiO3-3 wt.% MgF2 showed the best microwave dielectric properties of εr ∼18.09, Q × f ∼262,900 GHz (at 8.98 GHz) and τf ∼ −41.5 ppm/°C. The outstanding performance of MgF2 doped MgTiO3 ceramics provides a solid foundation for widespread applications of microwave dielectric substrates, resonators, filters and patch antennas in modern wireless communication equipment.

Microstructure and microwave dielectric characteristics of magnesium fluoride additive to MgTiO3-(Ca0.8Sr0.2)TiO3 ceramics

In this paper, the MgF2-doped (1 − x)MgTiO3-x(Ca0.8Sr0.2)TiO3 (x = 0.01–0.09) ceramics with high-quality factor (Q × f) and near-zero temperature coefficient of the resonant frequency (τf) were synthesized by solid-state reaction method. The effects of MgF2 addition on the phase composition, sintering behavior, and microwave dielectric properties in this system were completely investigated. Furthermore, the sintering temperature of 3 wt% MgF2-doped 0.95MgTiO3-0.05(Ca0.8Sr0.2)TiO3 ceramics can be lowered to 1225 °C. Then, the best microwave dielectric properties of εr ∼ 19.99, Q × f ∼ 90,100 GHz (at 8.72 GHz) and τf ∼ −2.9 ppm/°C were obtained. It provides a solid foundation for widespread applications of microwave dielectric substrates, filters, resonators, and patch antennas in modern wireless communication equipment.

Sintering behaviour and microwave dielectric properties of MgO/Eu2O3-doped 0.65CaTiO3–0.35SmAlO3 ceramics

0.65CaTiO3–0.35SmAlO3 ceramics (CTSA) were synthesized by the conventional solid-state method. To illustrate the effect of MgO/Eu2O3 additives and sintering temperatures on the dielectric properties of the CTSA ceramics, we performed qualitative and quantitative analyses. XRD analysis revealed that the perovskite phase was the main phase and a second phase Ca3Al2O6 appeared with steadily increasing Eu2O3 content in CTSA ceramics. The appropriate ratio of MgO/Eu2O3 additives resulted in a dense microstructure and excellent microwave dielectric properties, and lowered the sintering temperature from 1500 to 1315 °C. Excellent microwave dielectric properties of er = 45.32, Q × f = 43,600 GHz (at 5.0 GHz), and τf= − 1.1 ppm/°C were attained for 0.65CaTiO3–0.35SmAlO3 ceramics with 0.5 wt% MgO and 0.2 wt% Eu2O3 additives sintered at 1315 °C for 4 h.

Influence of Cr3+ substitution for Mg2+ on the crystal structure and microwave dielectric properties of CaMg1-xCr2x/3Si2O6 ceramics

Abstract The CaMg1-xCr2x/3Si2O6 (0 ≤ x ≤ 0.1) microwave dielectric ceramics were synthesized via conventional solid state reaction. In this study, the effects of Cr3+ substituting for Mg2+ on morphology, crystal structure and microwave dielectric properties of CaMg1-xCr2x/3Si2O6 ceramics were explored. XRD diffraction patterns exhibited that the CaMg1-xCr2x/3Si2O6 ceramics possessed the pure phase of CaMgSi2O6 when x ≤ 0.06 and a small amount of secondary phase Ca3Cr2(SiO4)3 for 0.08 ≤ x ≤ 0.1. SEM micrographs revealed that the substitution of Mg2+ with Cr3+ could decrease the grain size. The apparent density was affected by the concentration of Mg vacancies. The correlation between crystal structure and microwave dielectric properties was investigated through the Rietveld refinement and Raman analysis. The microwave dielectric properties were mainly dependent on relative density, ionic polarizabilities, internal strain Ƞ, disordered structure and MgO6 octahedron distortions. Finally, CaMg1-xCr2x/3Si2O6 (x = 0.02) ceramics sintered at 1270 °C for 3 h exhibited excellent microwave dielectric properties of er = 8.06, Q × f = 89054 GHz, τf = −44.92182 ppm/oC.

Dielectric properties of low Zr-substituted BaTi4O9 at microwave frequencies

The microwave dielectric properties and microstructures of Ba(Ti1−xZrx)4O9 (0≤ x ≤ 0.025) ceramics prepared using the conventional solid-state route were investigated. When x was increased from 0 to 0.0125, the Q × f value of the specimen increased from 32,600 GHz to a maximum of 63,700 GHz, and the er value increased from 34.6 to 35.5. The structure and microstructure were analyzed using X-ray diffraction and scanning electron microscopy. The dielectric properties were correlated with various x values. With x = 0.0125, the excellent microwave dielectric properties of er ~ 35.5, Q × f ~ 63,700 GHz (at 8 GHz), and τf ~ 13 ppm/°C were obtained for Ba(Ti0.9875Zr0.0125)4O9 ceramics sintered at 1300 °C for 4 h.

Microwave dielectric properties of ultra-low loss Li2Mg4Zr0.95(Mg1/3Ta2/3)0.05O7 ceramics sintered at low temperature by LiF addition

In this study, Li2Mg4Zr0.95(Mg1/3Ta2/3)0.05O7 (LMZT) ceramics were prepared via the conventional solid-state method. A cubic rock-salt structure with space group of Fm-3m was observed in all samples. Excellent microwave dielectric properties of εr = 12.68, Q × f = 190,403 GHz and τf = −20.64 ppm/°C were achieved for LMZT ceramic at 1500 °C. The variations in microwave dielectric properties were systematic investigated by polarizability, packing fraction and infrared spectrum. The complex dielectric loss was calculated from the fitting data of far infrared spectrum, which was in good agreement with the measured value. Moreover, the sintering characteristics, phase composition and microwave dielectric properties of LMZT-x wt.% LiF ceramics were researched. Dense microstructure could be gained at 1000 °C for 4 and 5 wt% LiF-doped LMZT ceramics due to liquid-phase sintering. The LMZT ceramics with 4 wt% LiF addition possessed excellent microwave dielectric properties: dielectric constant of 14.35, quality factor of 130,1030 GHz, temperature coefficient of resonant of −30.24 ppm/°C at 1000 °C.

Bond ionicity, lattice energy and structural evolution of Ta substituted 0.15ZnO-0.15Nb2O5-0.55TiO2 dielectric ceramics

In the present study, influences of Ta5+ substitution on Nb site on crystal structural evolution, Raman spectra and microwave dielectric properties of Zn0.15Nb0.3-xTaxTi0.55O2 (0 ≤ x ≤ 0.3) ceramics were investigated. Bond ionicity, lattice energy and octahedral distortion of Zn0.15Nb0.3-xTaxTi0.55O2 structure calculated based on chemical bond theory and Rietveld refinement analysis were used together to understand correlation between crystal structure and microwave dielectric properties. The results showed that rutile Zn0.15Nb0.3-xTaxTi0.55O2 solid solutions could be synthesized in whole composition range of x = 0–0.3. With increase of x value, cell volume and bond length are reduced, which is confirmed by blue shift of Raman vibrational peaks. Dielectric constant (εr) is closely related to average NbO bond ionicity. Quality factor (Q × f) values and temperature coefficient values of resonant frequency (τf) are mainly affected by lattice energy and octahedral distortion respectively. In Zn0.15Nb0.3-xTaxTi0.55O2 ceramics, proper substitution of Ta5+ ion efficiently improves Q × f values and reduces the τf values. Optimal microwave dielectric properties of εr = 75.87, Q × f = 22050 GHz and τf = 234.6 ppm/°C were obtained for Zn0.15Nb0.3-xTaxTi0.55O2 solid solutions at x = 0.2 when sintered at 1100 °C.

Phase structures, microstructures, and dielectric characteristics of high εr (1-x-y)Bi0.5Na0.5TiO3-xLi0.5Sm0.5TiO3-yNa0.5La0.5TiO3 microwave ceramic systems

Ultrahigh dielectric constant (εr) (1-x-y)Bi0.5Na0.5TiO3-xLi0.5Sm0.5TiO3-yNa0.5La0.5TiO3 (BNT-LST-NLT, 0.3 ≤ x ≤ 0.7, 0.0 ≤ y ≤ 0.4) microwave ceramic systems were fabricated using a conventional solid-state reaction method, and their phase structures, microstructures, and microwave dielectric characteristics were systematically investigated. From XRD pattern analyses and refinement results, (1-x-y)BNT-xLST-yNLT (x = 0.3–0.6 and y = 0.4–0.1) samples were crystallized into a cubic perovskite structure, and XRD peaks corresponding to the (031), (131), and (230) planes were identified as super-reflections belonging to the tilt system of orthorhombic a−a−b+ with the Pnma space group. In particular, on the basis of the Raman spectra and microwave dielectric properties analysis results, the crystal structure of the sample (x = 0.6 and y = 0.1) sintered at 1200 °C for 4 h was considered to be closer to orthorhombic symmetry. In addition, solid orthorhombic perovskite-type solutions were formed together with a small amount of secondary phase Sm2Ti2O7 as x = 0.6 and y = 0.2, 0.3. However, an increase in the Sm2Ti2O7 phase content was also detected for x = 0.7 and y = 0.0, accompanied by the perovskite phase. For the microwave dielectric properties, the εr and Q×f values strongly depended on the apparent density, ionic polarizability, phase structure, and phase composition, and also, the τf value was predicted by adjusting the tolerance factor (t). The εr and τf values basically agreed with the existing models, such as the mixing rule. As a result, the (1-x-y)BNT-xLST-yNLT (x = 0.6 and y = 0.1) ceramic sample sintered at 1200 °C for 4 h exhibited superior microwave dielectric properties of εr ~ 149.1, Q×f ~ 3270 GHz, and τf ~ 39.1 ppm/°C.