Temperature Coefficient Of Resonant Frequency Research Articles

Resolving the Role of Configurational Entropy in the Optimization of Mechanical, Thermal, and Microwave Dielectric Properties of SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 Ceramics.

The demand for high-performance microwave dielectric ceramics has surged with the proliferation of fifth-generation (5G) communication networks. In this work, SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 (x = 0-0.20) ceramics were designed by leveraging the unique properties of SrLaAlO4 ceramics and high-entropy engineering. The effects of configurational entropy (Sconf = 1.23R - 1.54R) on the mechanical, thermal, and microwave dielectric properties of SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 ceramics were investigated. X-ray diffractometer and transmission electron microscope analyses confirmed that each composition belonged to the tetragonal structure with a space group of I4/mmm. Significant improvements in Vickers hardness were observed with increasing Sconf, reaching 8.05 GPa at Sconf = 1.54R compared to 5.64 GPa in SrLaAlO4 ceramics. Additionally, the increasing entropy showed great potential in reducing the thermal expansion coefficient (CTE) from 12.32 to 11.49 ppm/°C. The optimal quality factor (Q × f) of 98,000 GHz was achieved at Sconf = 1.37R, attributed to the optimization of intrinsic lattice energy and infrared-damped modes. The temperature coefficient of resonant frequency (τf) was successfully modified toward zero due to entropy-driven CTE and structural modifications. Excellent microwave dielectric properties with εr = 22.5, Q × f = 98,000 GHz, and τf = -2.0 ppm/°C were obtained at Sconf = 1.37R. This work highlights the potential of entropy-engineering in developing high-performance microwave dielectric ceramics, offering a promising pathway for the advancement of 5G communication components.

Substitution of Ce4+ for ionic at both A/B sites greatly improves the microwave responses of (Sr0.9Ca0.1)1/2La1/2Al1/2Ti1/2O3 perovskite ceramics

In this paper, (Sr0.9Ca0.1)1/2La1/2Al1/2Ti1/2O3-x wt.% CeO2 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics were synthesized via solid state reaction. The effects of Ce4+ doping on microstructure and microwave dielectric properties were studied. All samples crystallized as perovskite single-phase. Ce4+ substitution for La3+ occurred at the A site for 0 < x ≤ 0.4, and for Ti4+ at the B site for 0.4 ≤ x ≤ 0.5. Oxygen vacancy concentration was linked to substitution sites, decreasing for x ≤ 0.3 and increasing for x ≥ 0.4, as shown by XPS analysis. The quality factor was influenced by oxygen vacancies, grain size, and packing fraction. Bonding valence and oxygen octahedral distortion affected the temperature coefficient of resonant frequency. At x = 0.4 and sintered at 1570 °C, the ceramics showed excellent properties: εr = 38.83, Q×f = 54058 GHz, τf = 2.137 ppm/°C, making it a promising low-loss dielectric ceramic for microwave communication applications.

Reaction-sintered highly transparent MgGa2O4 ceramics with enhanced dielectric properties

Reaction sintering of MgO and Ga2O3 powders was first used to prepare MgGa2O4 transparent ceramics. The microstructural evolution suggested that the negligible volume change resulting from the solid-phase reaction of MgO and Ga2O3, as well as the close and homogeneous arrangement of both fine particles, are the key factors in obtaining pre-sintered ceramics with an ideal microstructure at lower temperature. After a hot isostatic pressing (HIP) treatment, the fully dense ceramic exhibited improved in-transmittance (74.7%@600nm, and 85.4%@4401nm) and quality factor (Q×f=168000GHz). Due to the combination of high transparency, wide transmission range (6.22 μm at the 60% transmittance), ultra-low dielectric loss, and near-zero temperature coefficient of resonance frequency (–3.9 ppm/◦C), transparent MgGa2O4 ceramic is suggested to be an ideal optical-dielectric integration material.

Sintering behavior, lattice vibrational characteristics and dielectric properties of B-site ion substituted BaWO4 ceramics for LTCC applications

The influences of Mo6+ substitution at the B-site of scheelite structure on the sintering character, microstructures, lattice vibrational characteristics, and dielectric properties of BaW1-xMoxO4 (x = 0.10-0.30) ceramics were studied in detail in this paper. The sintering temperature of BaW1-xMoxO4 ceramics was effectively reduced to less than 950oC through forming a scheelite solid solution. The densification and the quality factor (Q×f) of BaW1-xMoxO4 ceramics were also enhanced compared with pure BaWO4 ceramic. Raman spectroscopy confirmed that the dielectric constant (εr) was highly correlated with molecular polarizability, and the Q×f was strongly dependent on the symmetric stretching bond of [WO4] tetrahedron. Oxygen bond valence was one of crucial parameters for modulating the temperature coefficient of resonant frequency (τf). Interestingly, the BaW0.75Mo0.25O4 ceramic sintered at 910oC exhibited favorable microwave dielectric properties of εr = 9.44, Q×f = 46,820GHz (@12.5GHz), and τf = −69.2 ppm/oC. Meanwhile, the BaW0.75Mo0.25O4 ceramic had stupendous dielectric properties in low-frequency band: εr = 17.5 and dielectric loss (tanδ) = 2.2×10-4 (@10MHz). In addition, there was good chemical compatibility between BaW0.75Mo0.25O4 ceramic and silver electrodes. These findings evidence that BaW1-xMoxO4 ceramics are competitive candidates in LTCC technology.

Influence of V substitutions on sintering behaviors and microwave dielectric properties of Ba4LiNb3O12 ceramic

AbstractIn this study, a series of Ba4Li(Nb1‐xVx)3O12 (x = 0.05∼0.3) ceramics were synthesized using the solid‐state reaction method. X‐ray powder diffraction (XRD) analysis shows that the composite ceramics contain both Ba4LiNb3O12 and Ba3(VO4)2 phases, without any other phases present. The grains consist of Ba4LiNb3O12 and Ba3(VO4)2, as illustrated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Additionally, with the increase of V content, the grain size decreases, and the (microwave dielectric constant) decreases, the (resonant frequency temperature coefficient) value decreases, and the value increases (where = quality factor = 1 / dielectric loss, and = resonant frequency). The densest Ba4Li(Nb0.7V0.3)3O12, with a of 31.3, of + 70 ppm/°C, and high of 42 850 GHz, was obtained at a sintering temperature of 1350°C. Furthermore, the addition of 5 wt.% BaCu(B2O5) (BCB) into Ba4Li(Nb0.7V0.3)3O12 resulted in obtaining dense ceramics at a sintering temperature of 925°C, with a of 23.5, a high value of 14 370 GHz, and of + 88 ppm/°C. Further investigations have shown that Ba4Li(Nb1‐xVx)3O12 ceramics are chemically compatible with Ag, suggesting its potential use in low‐temperature cofired ceramics technology.

Microstrip dielectric patch antenna fabrication and characterization using ultra low permittivity and low temperature Co-fired LiAlSiO4 ceramics

LiBxAl1-xSiO4 (x = 0.02–0.1) ceramics were prepared by conventional solid-state method with a reduction in sintering temperature by up to 250–475 °C. The relative permittivity was significantly decreased by εr = 3.3–3.7, one of the lowest ever reported values among crystalline ceramics, while maintaining exceptional quality factors (Q×f = 25,000–28,000 GHz) and low temperature coefficients of resonance frequency (τf = −23 ∼ −16 ppm/°C). Furthermore, these LiBxAl1-xSiO4 ceramics possess a low density (∼2.3 g/cm3), making them highly promising for lightweight microwave devices. The potential application of LiB0.1Al0.9SiO4 ceramics in LTCC was assessed based on their ability to achieve low densification temperature and exhibit chemical compatibility with silver electrodes. A microstrip patch antenna with an operating frequency of 6.68 GHz, featuring high efficiency (91.88 %) and wide bandwidth (400 MHz), has been designed and fabricated from LiB0.1Al0.9SiO4 ceramics substrate, which provides a good application prospect for advanced wireless systems. The development of these ultra-low permittivity dielectric ceramics opens new potential to revolutionize the field of microwave dielectric ceramics.

High thermal stability of the microwave dielectric properties of ZnNb2O6 with CaTiO3 addition

This paper presents a study of the dielectric properties of ZnNb2O6 (ZNO) with added CaTiO3 (CTO) in the microwave (MW) region. An X-ray diffraction analysis is performed, and a reaction between ZNO and CTO is demonstrated that results in the formation of other crystalline phases. The dielectric properties in the MW region show no significant change in permittivity (ε'r), whereas the addition of CTO results in an increase in the dielectric loss (tan δ). The thermal stability is also measured, and the temperature coefficient of resonant frequency (τf) is varied from −88.95 to −8.16 ppm °C−1. Numerical simulations are carried out to evaluate these materials for use as a dielectric resonator antenna, and the results show a reflection coefficient (|S11|) of below −10 dB, a radiation efficiency above 96 %, a bandwidth ranging from 100 to 170 MHz, and a gain of above 4.50 dBi. The values obtained here show that these materials could be employed in electronic devices acting in the C- and S-bands.

Improved microwave dielectric properties of LaZn1/2Ti1/2O3 through Y3+ substitution

LaZn1/2Ti1/2O3 is a double perovskite with promising microwave dielectric properties for applications towards dielectric resonators and antennas. Its dielectric properties can be enhanced through the substitution of suitable ions in either A- or B-sites. In this paper, we report a significant improvement in the quality factor (Q) by substituting Y3+ in the La site with a marginal reduction in dielectric constant (εr). A single phase is confirmed in XRD indicating the formation of La1-xYxZn1/2Ti1/2O3 (0 ≤ x ≤ 0.25) solid solutions. The substitution results in an expansion of lattice along the b direction while there is a contraction in both a and c directions, leading to a reduction in unit cell volume. The dielectric constant, εr, is observed to reduce from 33.4 to 29.6 due to the polarizability of A-site atoms. The temperature coefficient of resonant frequency (τf) increases with an increase in x which does not appear to correlate with reducing tolerance factor (t). This non-conventional behaviour of τf in this perovskite based solid solutions brings bond valence of O site (VO) into picture. VO appears to show competing effect on τf. The non-monotonic behaviour is observed in Q×f with a maximum value of 41,400 GHz at x = 0.15 and a sharp decline for x > 0.15. This observation is correlated with variations in the A-site bond valence (VA) and a long-range ordering (LRO) of B-site ions. LRO is associated with Ag mode at 710 cm−1 in the Raman spectra. The low frequency (< 250 cm−1) Raman modes shift to a higher frequency with the increase in Y3+. Y3+ substitution also induces lattice distortion which is discussed in terms of variations in FWHM and relative intensity of the Raman modes.

High-performance SiO2-Sr3(PO4)2 low-εr dielectric ceramics for MW/THz applications

We developed high-performance SiO2-based low-εr microwave dielectric composites via adding Sr3(PO4)2 and investigated their phase assemblages, sintering behaviors, microwave dielectric properties, thermal expansion coefficients (CTE), and mechanical strengths in this paper. Adding Sr3(PO4)2 into SiO2 could successfully suppress the occurrence of microcracks in SiO2, tune the values of both temperature coefficient of resonant frequency (τf) and CTE, and enhance the flexural strength of the composite simultaneously. The composite with 22.5 % volume fraction (Vf) of Sr3(PO4)2 exhibits excellent combined properties with a low-εr (∼5.35), high Q×f value ( ∼73,717 GHz), near-zero τf value(∼ −1.1 ppm/°C), suitable high CTE value (∼17 ppm/°C), and acceptable high flexural strength (∼85Mpa) after sintering at the temperature of 1150°C/3 h.

Sintering behavior, zinc volatilization, microstructure and microwave dielectric properties of ZnxSiO2+x ceramics

In this paper, the evolution of the microstructure for the zinc silicate ceramics with different Zn/Si ratios was revealed, and the factors influencing their dielectric properties were discussed. Our results demonstrate that Zn volatilization plays an important role on the defect structure of the samples. Low relative density, high conductivity loss caused by volatilization, and the presence of ZnO phase collectively result in low quality factor (Qf) of Zn2.0SiO4.0. By using the powder embedded sintering method, the loss could be reduced owing to the suppression of volatilization. As the Zn/Si ratio decreases, the ZnO disappears, while the Si-rich phase emerges and increases. The formation of a liquid phase results in a dense microstructure of the non-stoichiometric samples. Moreover, these samples exhibit a minor degree of Zn loss, probably because the presence of liquid phase constraints the volatilization during sintering. The samples with x = 1.8 display desirable properties, including a relative dielectric constant (εr) of 6.5, a Qf of 100,800 GHz, and a temperature coefficient of resonant frequency (τf) of −21.3 ppm/°C, due to their high degree of densification, slight zinc loss, and the elimination of the ZnO phase.

Near-Zero Temperature Coefficient of Resonance Frequency in Rare-Earth Titanates via the Phase Transition Strategy.

This study presents an approach to achieve a near-zero temperature coefficient of resonance frequency (τf) in rare-earth titanate microwave dielectric ceramics (MWDCs) by inducing a phase transition. By Zr4+ substitution at the B site, a series of Sm2Ti1-xZrxO5 (0.02 ≤ x ≤ 0.55) ceramics are synthesized using the solid-state method to intentionally alter the radius ratio of the A/B sites, realizing in a controlled phase transition from orthorhombic (Pnma) to biphasic coexistence and ultimately to cubic (Fd3̅m) structure. The phase composition is rigorously identified through X-ray diffraction (XRD) Rietveld refinement, high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), and Raman spectroscopy. A comprehensive analysis is conducted to elucidate the relationships between factors such as ionic polarizability, packing fraction, bond valence, complex chemical bonding, and far-infrared reflectivity spectra with microwave dielectric properties. The results demonstrate that these ceramics exhibit a broad range of permittivity (14.30-23.18), high-quality factors (14,828-22,300 GHz), opposite temperature coefficient of resonance frequency (-16.0 to + 22.4 ppm/°C), and nice thermal conductivity (1.81-2.76 W·m-1·K-1), particularly at x = 0.30 with a near-zero τf value of +1.6 ppm/°C. The findings not only provide insights into designing MWDCs with a near-zero τf but also offer a promising route for developing advanced microwave materials with improved performance and reliability.

A novel Li3Mg4(Nb1-xVx)O8 ceramic with high Q×f value and good temperature stability with low sintering temperature

A series of low-loss Li3Mg4(Nb1-xVx)O8 (0.02 ≤ x ≤ 0.08) ceramics has been synthesized in this work, with the optimal sintering temperature lowered to 950°C due to the incorporation of V5+ ions. Moreover, the effects of substituting V5+ for Nb5+ on the sintering, composition, structure and properties of the ceramics have been systematically analyzed. It has been discovered that the permittivity (εr) and quality factor (Q×f) of Li3Mg4(Nb1-xVx)O8 ceramics exhibit a correlation with the relative density, which is influenced by the variation in grain size distribution resulting from the substitution of V5+ ions. Additionally, the total lattice energy of Li3Mg4(Nb1-xVx)O8 ceramics is also affected by the bond characteristics within the Nb-O octahedra, thus influencing the Q×f value. The resonant frequency temperature coefficient (τf) fluctuates within a small range. The Li3Mg4(Nb0.98V0.02)O8 ceramics exhibit excellent microwave dielectric properties at 950°C: εr∼14.03, Q×f∼93,425 GHz, τf∼-6.12 ppm/°C, with a relative density reaching 98.3 %. Compared to unsubstituted Li3Mg4NbO8 ceramics, the sintering temperature is reduced by 200°C without forming impurity phases. While adjusting the τf value to nearly zero, it maintains a high Q×f value, indicating promising applications in Low-Temperature Co-fired Ceramics (LTCC).

Influence of structural characteristics of Ca1-xNdxW1-xVxO4 ceramics on microwave dielectric properties

Dense Ca1-xNdxW1-xVxO4 (x = 0−0.4) microwave dielectric ceramics were obtained when sintered at 1150 °C for 4 h. A tetragonal scheelite could be formed in the range of x ≤ 0.3, while a composite region with tetragonal scheelite and tetragonal zircon was found at x ≥ 0.4. The relative permittivity (εr) increased from 10.15 to 13.66, mainly attributed to an increase in the ionic polarizability. The quality factor (Q×f) decreased from 61,060 to 32,204 GHz, correlated to the variations in lattice energy and the Raman FWHM. The temperature coefficient of resonant frequency (τf) gradually increased from −54.03 to −23.50 ppm/℃, mainly affected by the rattling effect of W6+/V5+ and the temperature coefficient of ion polarizability (ταm). Ca0.7Nd0.3W0.7V0.3O4 with excellent comprehensive properties (εr = 13.21, Q×f = 35,570 GHz, and τf = −23.50 ppm/°C) were obtained at 1150 °C.

Structures and properties of LiBaF3 microwave dielectric ceramics for ULTCC applications

Perovskite structural LiBaF3 ceramics with excellent microwave dielectric properties were synthesized using traditional solid-state method. By regulating the sintering temperatures from 600 °C to 675 °C, LiBaF3 ceramics exhibit tunable dielectric constant (εr) from 12.42 to 13.72, adjustable Q × f value from 55000 GHz to 73000 GHz, and regulable temperature coefficient of resonance frequency (τf) from −36.78 ppm/°C to −34.68 ppm/°C. The properties are strongly associated with the density, and can be further optimized by 0.5 wt%TiO2 addition (εr = 14.43, Q × f = 56000 GHz, τf = -1.26 ppm/°C). The LiBaF3 ceramics also exhibit excellent compatibility with Ag and Al electrodes. Furthermore, relationships between multiscale structures and microwave dielectric properties of the ceramics were revealed. Oxidation behaviors between LiBaF3 and O2 would result in the lattice shrinkage, the introduction of defect level, the decrease of bandgap and density, and then deteriorating the microwave dielectric properties. All the findings make the LiBaF3 ceramic a promising candidate for ULTCC application, and may facilitate the development of other novel microwave dielectric materials.

Crystal structure and microwave dielectric properties of BaZn(1-x)CoxP2O7 ceramics

BaZn(1-x)CoxP2O7 (0 ≤x≤ 0.125) ceramics were synthesized using the solid-state reaction method, with sintering temperatures ranging from 875 °C to 975 °C. The study systematically investigated the phase composition, crystal structure, and microstructure of the ceramics, and correlated these characteristics with their dielectric properties. Additionally, density functional theory (DFT) was employed to examine the energy band structure, electron density, and density of states of the materials. The dielectric constant εr values were primarily influenced by polarizability, while the Q × f values of BaZn(1-x)CoxP2O7 ceramics were predominantly affected by the packing fraction and full width at half maximum (FWHM). The temperature coefficient of resonant frequency was influenced by a decrease in bond valence and an increase in PO4 tetrahedral distortion. Notably, the BaZn0.975Co0.025P2O7 ceramic demonstrated promising microwave dielectric properties, with εr = 8.15, Q × f = 42,431 GHz, and τf = −27.5 ppm/°C, when sintered at 950 °C for 4 h.

Structure and microwave dielectric characteristics of (Ba,Sr,Ca)HfO3 ceramics

In the present work, the structure and microwave dielectric properties of (Ba,Sr,Ca)HfO3 ceramics were systematically investigated to understand the general mechanism of tuning the temperature coefficient of resonant frequency, τf in perovskite ceramics. Ba1–xSrxHfO3 and Sr1–yCayHfO3 could form continuous solid solutions while the solid solubility of Ca in Ba1–yCayHfO3 was about 20% (in mole). τf changed nonlinearly with increasing tolerance factor as the result of competition between the increase in the restoring force on the ions and the increase in polarizability. Under the guidance of three microscopic mechanisms affecting τf, a preliminary attempt was made to explore the suitable parameters to predict the variation trend of τf. Normalized ionic radii and the τf values of the end members were selected as independent variables, and τf was calculated by using multiple linear regression method. For Ba1–xSrxHfO3 and Sr1–yCayHfO3 with orthorhombic structures, the root mean square error between the calculated and measured τf was only 6.8×10–6 °C–1. The good agreement between the calculated τf values and the measured ones in Ba1–x–ySrxCayHfO3 ceramics confirmed its validity where three elements jointly occupy A-site, but it only works when there is no structural phase transition. Progresses in this research field would not only deepen our understanding of mechanism of regulating properties in multi-ion solid solutions, but also boost the developments of closely related fields such as machine learning-assisted design and high-entropy ceramics. Finally, a good combination of microwave dielectric properties was achieved in Sr0.15Ca0.85Hf0.96Ti0.040O3: εr = 27.8, Qf = 36,470 GHz, τf = +5×10–6 °C–1.

Microwave properties of SrY2O4 spinel synthesized for advanced applications

This study investigated the microwave dielectric properties and microstructures of SrY2O4 ceramics fabricated using the conventional solid-state route. The investigation revealed that the dielectric constant (ε r ) values exhibited saturation behavior, reaching a plateau within the range of 14–15. Notably, high quality factor (Q⋅f) values ranging from 64,500 to 92,000 (measured at 11 GHz) were achievable when sintering temperatures were maintained between 1480 and 1520 °C. Furthermore, the temperature coefficient of resonant frequency (τ f ) demonstrated minimal sensitivity to variations in sintering temperature. Significantly, SrY2O4 ceramics sintered at 1520 °C for 4 h exhibited a desirable combination of microwave dielectric properties, including a high ε r value of 15, an exceptional Q⋅f value of 92,000, and a favorable τ f value of −6.2 ppm/°C. These findings suggest the potential of SrY2O4 ceramics, particularly under these specific sintering conditions, for applications in microwave devices.

Optimizing microwave dielectric properties of low‐temperature sintered Sr/Zn‐substituted BaMg2V2O8 by mixing with TiO2

AbstractBa1 − xSrxMg2 − yZnyV2O8 compounds, abbreviated as BSMZVO@xy (x = 0.0–0.2 and y = 0.02), were synthesized with tetragonal structures. The microstructure, molecular structure, and polarization mechanism were investigated using X‐ray diffraction, electronic microscopy, Raman spectroscopy, and vector network analyzer. The sintering temperatures (&lt;900°C) and microwave dielectric properties of BSMZVO are significantly impacted by (Sr/Zn)2+ substitution and TiO2 mixing. The BSMZVO@xy (x = 0.15 and y = 0.02) exhibited encouraging εr (12.4–12.7), Q × f (40 054–40 973 GHz), and temperature coefficient of resonance frequency (τf ∼ −5.2 to 0.0 ppm/°C) after sintering at 860°C/4 h and 800°C/4 h. For the first time, TiO2 was added to enhance the density and Q × f value without degrading τf. The 0.25 wt.% TiO2 resulted in optimum εr of 13.4, Q × f of 43 636 GHz, and τf of +1.8 ppm/°C after sintering at 760°C/4 h. The improved quality factor (Q × f) is linked to the Raman A1g mode and relative density.

The entropy effect on the structure and microwave dielectric properties of high-entropy Lix(MgZnCoNi)(1-x)/4Al2O4-δ ceramics

In present study, high-entropy Lix(MgZnCoNi)(1-x)/4Al2O4-δ ceramics (x = 0.00–0.45) were synthesized using solid-state reaction route, which formed a single-phase spinel structure with a Fd-3m space group. The reduction in unit cell volume and lattice parameters were attributed to the compression of polyhedral structures. A moderate content of Li+ ions promoted the grain growth and improved the densification of ceramics. The internal connection among the conformational entropy (ΔSconfig), structure, and microwave dielectric properties in high-entropy Lix(MgZnCoNi)(1-x)/4Al2O4-δ ceramics was systematically studied. The dielectric constant (εr) was largely affected by the polarizability, and relatively high conformational entropy helped to increase the phonon vibrational energy and enhance the bond strength, resulting in low εr values. Additionally, the high concentration of oxygen vacancies, high packing fraction, low internal strain/fluctuation and suppressed damping behavior were closely related to relatively low conformational entropy. Notably, the introduction of oxygen vacancy leaded to the Al3+ ions preferentially occupy tetrahedral sites enhancing the covalency. These factors collectively reduced the intrinsic losses and improved the quality factor (Q×f). Moreover, relatively high conformational entropy conduced to the structural stability by improving the M-O (M = Li, Mg, Zn, Co, and Ni) bond strength and valence, which contributes to achieve near-zero temperature coefficient of resonant frequency (τf). As ΔSconfig changes, high-entropy Lix(MgZnCoNi)(1-x)/4Al2O4-δ ceramics presented great microwave dielectric properties: εr values of 5.46 ∼ 8.49, Q×f values of 3,540 GHz (f = 14.84 GHz) ∼ 56,950 GHz (f = 12.99 GHz), and τf values of −58 ppm/°C∼ −14 ppm/°C. Our study demonstrates that the high-entropy strategy effectively enhances microwave dielectric properties. This approach has potential applications across a broad spectrum of microwave dielectrics ceramics.

Relationship between structure and microwave dielectric properties of new low-K garnet-type Ca3Cr2Ge3O12 ceramics

In order to solve the problem of signal delay, a novel low-K Ca3Cr2Ge3O12 ceramic for 5G and millimeter-wave communication was prepared by a solid-state reaction method. XRD and Rietveld refinement results confirm that it belongs to the garnet structure with the Ia-3d space group. The shrinkage rate of the sample sintered at 1350 °C reached 11.9 %, and the relative density exceeded 94.3 %. Excellent microwave dielectric properties were obtained. The permittivity was 8.38, the quality factor was 23,107 GHz, and the temperature coefficient of resonant frequency was −43.57 ppm/°C. The relationship between the crystal structure and microwave dielectric properties of ceramics was further studied. The results show that lattice vibration, stacking fraction and bond strength have a great influence on the Q × f value of ceramics, and the bond valence parameter is the key factor affecting the temperature stability. In addition, the theoretical quality factor of the ceramic can reach ∼13,0000 GHz by far-infrared reflection spectroscopy, and the ceramic has great research potential. The development of Ca3Cr2Ge3O12 ceramics and the study of microwave dielectric properties have filled the research gap of related systems. The excellent microwave dielectric properties indicate that it can be used as an alternative material for the preparation of components in the field of communication.