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High Q·f value and temperature-stable MgF 2 -doped MgTi 1-x (Mn 1/3 Sb 2/3) x O 3 ceramics have been successfully prepared by the solid-state reaction method. Microwave dielectric properties and sintering performance of MgF 2 -doped MgTi 1-x (Mn 1/3 Sb 2/3) x O 3 ceramics were systematically investigated by the classic theory and the P-V-L theory. The results show that MgF 2 doping and complex cation (Mn 1/3 Sb 2/3)4+ substitution not only further reduces the sintering temperature of MgTiO 3 ceramics from 1400 °C to 1250 °C, but also effectively improves the quality factor from 110210 GHz to 228713 GHz and adjust the τf value from −53.55 ppm/°C to −20.42 ppm/°C. The ionicity, the bond valence and octahedral distortion confirmed that Ti/(Mn 1/3 Sb 2/3)-O bonds exert a greater influence on microwave dielectric properties than Mg-O bonds in MgTiO 3 ceramics, which provides a guide to further improve the microwave dielectric performances. The optimal microwave dielectric properties: ε r = 18.8 ± 0.28, Q·f = 228713 ± 2500 GHz (at 6.08 GHz), τ f = (−20.42 ± 1.1) ppm/°C were achieved for 3 wt% MgF 2 doped MgTi 0.99 (Mn 1/3 Sb 2/3) 0.01 O 3 ceramics sintered at 1250 °C. [ABSTRACT FROM AUTHOR]

Ceramics of Li 2 Mg 2 GaTi 2 O 8 F (LMGTOF) were prepared by the traditional solid-state method. XRD and TEM results confirmed that a single phase of Li 2 Mg 2 GaTi 2 O 8 F, with an Fd-3m space group and a cubic spinel structure, was formed by the ceramics. It was shown by the results that the lattice parameters of the ceramics at 1050 °C were measured as a = b = c = 8.36576 Å, with a volume of V = 585.485549 Å3. Furthermore, it was observed through the analysis of the Raman peak at 718 cm−1 that an inverse relationship was exhibited between the Raman shift and ε r. Similarly, an opposing trend was also demonstrated between the Q × f value and FWHM. By bond valence analysis, it was shown that Mg2+, Ga3+, and Ti4+ ions were in a "rattling" state, and the large positive deviation between ε corr and ε theo was attributed to the strong "rattling" effect induced by the cations. At 1050 °C, the best microwave dielectric properties (ε r = 14.58, Q × f = 76,689 GHz, and τ f = −52 ppm/°C) were exhibited by LMGTOF ceramics. [ABSTRACT FROM AUTHOR]

In this paper, Ce 2 [Zr 1− x (Cd 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1− x (CS) x M, x = 0.01–0.1) were prepared via the conventional solid-state method. XRD and Rietveld refinement analyses confirmed the formation of a single-phase CZ 1− x (CS) x M solid solution with a space group of R -3c(167). The sintering behavior of the samples were investigated using SEM and relative density, which showed that optimal densification for CZ 0.98 (CS) 0.02 M ceramics were achieved at 675 °C with an average grain size of 1.70 μm. The P-V-L theory revealed the significant influence of the Zr(Cd/Sb)-O bond on the dielectric properties of CZ 1− x (CS) x M ceramics. Furthermore, far-IR reflectance spectra indicated that the measured dielectric loss value (1.04 × 10−4) is in line with the calculated value (1.60 × 10−4), suggesting a substantial impact of phonon oscillation absorption on the dielectric properties. Notably, CZ 0.98 (CS) 0.02 M ceramics demonstrated superior performance at 675 °C, with ε r = 10.44, Q × f = 93,152 GHz (at 12.96 GHz), and τ f = −17.73 ppm/°C. [ABSTRACT FROM AUTHOR]

This study examines the low‐loss and temperature‐stable Na2O–Ln2O3–MoO3–TiO2 (Ln = Nd, La and Ce) system, synthesized via a solid‐state process at low‐sintering temperatures ranging from 840°C to 900°C The structure, microstructure and microwave properties of the Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce) ceramics as a function of the sintering temperature were studied. The results of XRD patterns and microstructure characterization showed that the main phase in compositions belong to tetragonal scheelite and tetragonal structure. The ceramic composition Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce), sintered at 840°C–900°C for 2 hours, demonstrated excellent microwave dielectric properties, exhibiting relative dielectric constant (εr) of 13.9–14.4, Q × f value of about 31 100 (at 9.66 GHz) – 48 600 GHz (at 9.33 GHz), and temperature coefficient of –8.1 to –1 ppm/°C. Our work designs temperature‐stable microwave dielectric ceramics with low‐sintering temperature for LTCC technology applications. [ABSTRACT FROM AUTHOR]

In this study, the element substitution technique was utilized to create a solid solution, which in turn allowed for the manipulation of lattice parameters. The microwave dielectric properties of Mg 1.8 R 0.2 Al 4 Si 5 O 18 (R=Mg, Ni, Zn, Cu, Sr, Ca, Ba) ceramics were investigated following the substitution of Mg2+ ions. The influence of microstructural alterations on these properties was also examined. A cordierite solid solution was formed when R = Ni, Cu, Sr, or Ba; however, an additional phase emerged when R = Zn, Sr, or Ca. The complete substitution influenced the relative dielectric constant of Mg 1.8 R 0.2 Al 4 Si 5 O 18 due to the ionic polarizability and the average ionic property of the R ion. The Q × f value was found to be related to the crystal lattice energy, while the τ f value was primarily affected by octahedral distortion. The appearance of a secondary phase altered the primary factors influencing the dielectric properties of the Mg 1.8 R 0.2 Al 4 Si 5 O 18 ceramics. Among the substitutions tested, Mg 1.8 Ni 0.2 Al 4 Si 5 O 18 exhibited superior microwave dielectric properties with ε r = 4.64, Q × f = 44,770 GHz, and τ f = −32 ppm/°C. [ABSTRACT FROM AUTHOR]

Inorganic oxide ceramics are essential for microwave applications due to their stable structure and exceptional performance. LiZnMgGaTi 2 O 8 ceramics were prepared using the solid-phase method. XRD and TEM confirmed that the ceramics possess spinel structures. The ceramics had a maximum relative density of 94.57 % and a Vickers hardness of 8.58 GPa when sintered at 1220 °C. The ionic polarizability of Ti4+ in the ceramics exceeds the Shannon value, leading to a 20.3 % deviation between ε th and ε r. The activation energy of the impedance spectrum fitting is 1.302 eV, indicating a low concentration of oxygen vacancies in the ceramic. Hence, the Q × f value of the ceramics is primarily influenced by relative density. The optimal microwave dielectric properties of LiZnMgGaTi 2 O 8 ceramics are ε r = 15.68, Q × f = 66,620 GHz, and τ f = −30.9 ppm/°C. The test curves of ε r and dielectric loss remain nearly parallel to the x-axis from −80 °C to 80 °C, demonstrating the excellent stability of LiZnMgGaTi 2 O 8 ceramics. [ABSTRACT FROM AUTHOR]

Ba1 − 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 (<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. [ABSTRACT FROM AUTHOR]

Ba1 − 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 (<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. [ABSTRACT FROM AUTHOR]

Mg1/3A11/3A21/3Ta2O6 ceramics (where A1 and A2 represent Co, Ni, or Zn) were prepared using the solid‐phase reaction route. The results of X‐ray diffraction and Raman tests showed that (Co1/2Ni1/2)2+, (Co1/ 2Zn1/2)2+, and (Ni1/2Zn1/2)2+ ions replaced Mg2+ ions in the lattice of MgTa2O6, resulting in the formation of a pure tri‐rutile structure. All three complex ions could significantly reduce the sintering temperature of the ceramics (by 150°C–200°C) and could broaden the sintering window. The large deviation (48.8%–69.2%) between the porosity corrected relative permittivity εr‐corr. and the theoretical relative permittivity εr‐theo. might be due to the overestimation of the ionic polarizability of Ta5+ by Shannon. (Co1/2Ni1/2)2+ has the most significant effect of increasing the bond energy of ceramic A–O bonds, reducing the τf value from 51 to 36 ppm/°C. In addition, the mechanisms affecting their dielectric properties are discussed based on bond ionicity (fi), full width at half maximum (FWHM) of Raman peak, and bond energy (E). Mg1/3Co1/3Ni1/3Ta2O6 ceramic sintered at 1350°C have the most excellent microwave dielectric properties: εr = 26.8, Q × f = 86,000 GHz, and τf = 36 ppm/°C. [ABSTRACT FROM AUTHOR]

The LiVO 3 ultra-low temperature cofired ceramic (ULTCC) was synthesized by the solid-state chemical method and its crystal structure, sintering behavior, and microwave dielectric performances were systematically studied by X-ray diffractometer (XRD) and Scanning electron microscope (SEM). XRD showed that LiVO 3 were pure monoclinic single phase with a space group of C2/c. Furthermore, the best microwave dielectric properties Q × f = 16,900 ± 720 GHz, ε r = 8.78 ± 0.06, and τ f = − 117 ± 2.3 ppm/°C could be obtained when LiVO 3 sintered at optimal sintering condition 520 °C/8 h affirmed by SEM. The microwave dielectric properties were also deeply investigated utilizing the P–V–L chemical bond theory. The microwave dielectric performances of LiVO 3 had a great closer relationship with the V(1)–O bonds explained by analysis data. The low permittivity LiVO 3 with attractive features highlighted it to be a good candidate for ULTCC applications. [ABSTRACT FROM AUTHOR]

As communication technology continues to evolve, 5G technology is becoming more mature, and 6G technology is steadily advancing. Microwave equipment is moving toward high frequency, miniaturization, low loss and high temperature stability, and microwave dielectric ceramics have been deeply applied in this field. To elevate the Q × f value of CoNb2O6 system, Ta5+ was introduced into CoNb2O6, and CoNb2‐xTaxO6 (0.0 ≤ x ≤ 0.8) ceramics were prepared by the traditional solid‐phase method. By X‐ray diffraction, it was observed that at x = 0.8, in addition to a single niobium ferrite phase, information of tantalate phase also appeared. Raman spectral detection and group theory analysis indicate that Ag(2) and Ag(3) modes are the dominant Raman vibrations at ≈873 cm−1. Furthermore, the polarization rate affects the εr value, and the bond energy of Nb/Ta‐O and the recovery force characterized by the average deformation of the [Nb/TaO6] octahedron are the key elements influencing the temperature coefficient of the resonance frequency (τf). The internal strain, ordered induced size, and chemical bonding valence of ionic valence states are the key factors that can increase the Q × f value. Moreover, the introduction of ions with lower electronegativity leads to an enhanced electronic compensation of oxygen vacancies, which also reduces the dielectric loss. This paper enriches the theory related to low dielectric loss and shows that CoNb1.8Ta0.2O6 (εr = 21.4832, Q × f = 100723 GHz, τf = ‐61.38 ppm/°C) ceramics with superior microwave dielectric properties are expected to be used in wireless communication devices. [ABSTRACT FROM AUTHOR]

Calcite, as the thermodynamically stable phase of calcium carbonate, is a promising low-cost candidate as low- ε r microwave dielectric ceramics because of its large natural reserve and the strong covalency of C–O bond, while it is difficult to be densified due to the decomposition at about 627 °C. In the present work, calcite ceramics with the relative density of 87.8 % and low Qf value of 5,600 GHz were prepared by the room-temperature cold sintering, and the pressure-less sintering at 400–600 °C was conducted subsequently. The pressure-less sintering only increases the relative density slightly, while the microstructural evolution including the formation of uniform grains and significant grain growth were observed with increasing the sintering temperature, leading to a dramatic increase in Qf value. The best microwave dielectric properties with ε r = 7.60, Qf = 20,200 GHz, and τ f = −154 ppm/°C at around 12 GHz were obtained in the calcite ceramic sintered at 600 °C, indicating the applicable possibility of carbonate ceramics in microwave communications. [ABSTRACT FROM AUTHOR]

A series of (Mg 1- x Zn x) 3 (PO 4) 2 (x = 0.02–0.10) microwave dielectric ceramics were fabricated by the solid-state reaction method and investigated in terms of crystal structure, chemical bond properties, and dielectric properties were analyzed. The XRD data indicates that (Mg 1- x Zn x) 3 (PO 4) 2 samples belong to the monoclinic crystal with P 2 1 /c space group and no detectable secondary phases. The Rietveld refinement was employed to obtain crystal parameters. In addition, the results of chemical bond properties reveal that the lattice energy and ionicity of Mg (2)–O (3) bonds play a primary effect on the dielectric loss and dielectric constant, respectively. The bond energy of Mg(l)-O (2) bonds plays a dominant role in thermal stability. The far-infrared spectroscopy was employed to explore the intrinsic dielectric parameters, and the results showed that peaks below 400 cm-l contributed 78.9 % to ε′ and 99.1 % to ε″. The Raman data demonstrated that the Raman shift and FWHM exhibit an important influence on Q × f. The optimal performance was achieved in (Mg 0.94 Zn 0.06) 3 (PO 4) 2 ceramics: ε r = 5.00, Q × f = 84,674 GHz, τ f = −59.98 ppm/°C. [ABSTRACT FROM AUTHOR]

A series of microwave dielectric ceramics, (1-x)Na 0.5 Y 0.5 MoO 4 -xNa 0.5 Bi 0.5 MoO 4 , with low sintering temperatures and excellent microwave dielectric properties, were prepared by solid-state reaction. The ceramics were sintered well at 820 oC, and the structure, microwave dielectric properties, and chemical compatibility were investigated. When x=0.1, the microwave dielectric constant (ε r), the quality factor (Q × f value), and the temperature coefficient of resonant frequency (TCF value) of the 0.9NYM-0.1NBM ceramic were 10.9(±0.2), 54,060(±1,000) GHz, and -48.6(±1) ppm/°C, respectively. When x=0.7, the ε r of the 0.3NYM-0.7NBM ceramic was 23.6(±0.5), the Q × f value was 19,020(±400) GHz, the TCF value was -3.1(±0.1) ppm/°C and the room temperature thermal conductivity was 1.21(±0.01) W/(m.K). After co-firing with 20 w.t. % silver powder at 820 °C, it was found that (1-x)NYM-xNBM ceramics were chemically compatible with Ag electrodes, indicating their potential as alternative materials for low-temperature co-fired ceramics (LTCC). [ABSTRACT FROM AUTHOR]

Recently, microwave dielectric ceramics with an oxyfluoride cubic rock salt structure have been widely studied due to their excellent microwave dielectric properties. However, the sintering mechanism of this material, especially the role of F-ions, is not clear. Here, the ceramic samples with two different LiF addition strategies were prepared by a conventional solid-phase reaction method. The sintering mechanisms of both samples were discussed in detail by analyzing the sintering activation energy, F-ions distribution, and concentration of oxygen vacancies by linear shrinkage, SEM-EDS, and XPS. The best microwave dielectric properties were obtained for Li 2 MgTiO 4 +4 wt% LiF (LiF-B) ceramics sintered at 950°C: ε r = 18.0, Q×f = 82,100 GHz, and τ ƒ = −32.7 ppm/°C. [ABSTRACT FROM AUTHOR]

Here, a low-loss and low sintering temperature Zn 3- x Cu x (VO 4) 2 (ZCuVO) (x = 0.06) ceramic with two phases has been developed. The addition of Cu2+ induced the Zn 3 (VO 4) 2 (ZVO) ceramic to catalyze a small amount of the Zn 2 V 2 O 7 phase. The macroscopic manifestations of weight loss and heat flow reveal the sintering behavior of ZCuVO ceramics. Final formation and densification of ZCuVO ceramics in the range of 700–825 °C. The addition of trace amounts of Cu2+ promoted the critical melt-state of grains, the improvement of the density, the change of the molecular polarization, and the degree of structural ordering, which ultimately manifested itself in the further enhancement of the microwave dielectric properties. The results show that a moderate amount of Cu2+ substitution can modulate ε r , improve the Q×f value, and increase the τ f value. The ZCuVO (x = 0.06) ceramic sintered at 775 °C showed excellent performance (ε r = 12.62, Q×f = 38798.56 GHz, and τ f = −69.29 ppm/°C). This study shows that this ceramic has good potential for LTCC applications and provides a reference for the critical melting state of the grains to enhance microwave dielectric properties. [ABSTRACT FROM AUTHOR]

The effects of Ca2+ substitution for Ba2+ in BaZnP 2 O 7 ceramics on the phase composition, sintering behavior, and microwave dielectric mechanism were systematically investigated. When x ≤ 0.02, the ceramics crystallized into a single-phase solid solution of BaZnP 2 O 7 , whereas samples with x ≥ 0.04 showed mixed phases of BaZnP 2 O 7 and CaZnP 2 O 7. The sintering behavior was ameliorated by Ca2+ substitution, and the sintering temperature of Ba 1- x Ca x ZnP 2 O 7 (0 ≤ x ≤ 0.1) was reduced from 920 to 840 °C effectively. The Raman spectra and P–V-L theory confirmed that the compressed P–O bond caused by Ca2+ substitution is beneficial to reducing the lattice anharmonic vibration and enhancing the lattice energy (U), which is conducive to the improvement of the Q × f value of the Ba 1- x Ca x ZnP 2 O 7 ceramic when x = 0.02. Excellent microwave dielectric properties were obtained for the Ba 0.98 Ca 0.02 ZnP 2 O 7 ceramic after sintered at 880 °C for 4 h, i.e., ε r = 8.29, Q × f = 84,116 GHz, τ f = −23.84 ppm/°C. [ABSTRACT FROM AUTHOR]

This study investigates the synthesis, structural analysis, and microwave dielectric characteristics of ZnZrNb2O8 ceramics, prepared via solid-state reaction method and subjected to sintering at temperatures ranging from 1,000°C to 1,200°C for 4 h. X-ray diffraction (XRD) analysis confirms the successful formation of ZnZrNb2O8 phase, with a monoclinic wolframite phase. Scanning electron microscopy (SEM) investigations unveil microstructural features such as grain size and porosity, reveals material's morphological details. Dielectric properties conducted in the microwave frequency regime show a correlation between dielectric constant (εr) and relative density of the ceramics. Importantly, the ceramics exhibited a suitable dielectric constant and low dielectric loss, indicative of their suitability for microwave applications. Remarkably, ZnZrNb2O8 ceramics sintered at 1,150°C for 4 h exhibit excellent microwave dielectric properties (εr = 27.2, Q × f = 54,500 GHz, and τf = -60 ppm/°C). These findings underscore the potential of ZnZrNb2O8 ceramics as advanced materials for high-frequency applications, including filters, resonators, and other microwave devices, thus contributing significantly to the advancement of next-generation telecommunications technologies. [ABSTRACT FROM AUTHOR]

In this work, MgF 2 – x wt%LiF (x = 0.5, 1.0, 2.5, 4.0, 5.0) ceramics have been prepared through the standard solid-state reaction method. X-ray diffraction patterns and scanning electron micrographs revealed the successful preparation of dense MgF 2 –LiF composite ceramics at an exceptionally low sintering temperature range of 525–600°C. The optimal microwave dielectric properties (ε r = 5.09 ± 0.03, Qf = 100,733 ± 1646 GHz, τ f = −67.4 ± 3.3 ppm/°C) were achieved in MgF 2 –0.5 wt%LiF ceramics after sintering at 550 °C for 3 h. The present ceramics exhibited an outstanding combination of low- ε r , high Qf , and an ultra-low sintering temperature, surpassing the performance of most low-temperature-fired dielectric materials. Moreover, the theoretical Qf value, extrapolated from the fitting of infrared reflectivity spectra, was calculated to be 326,583 GHz, indicating significant potential for further Qf improvement. Additionally, the chemical compatibility with Al electrodes was confirmed, suggesting promising potential for ultra-low temperature co-fired ceramic (ULTCC) applications. [ABSTRACT FROM AUTHOR]

Dielectric ceramics with low permittivity (εr), high quality factor (Q×f), and near-zero resonant frequency (τf) in the microwave bands are key materials used in fifth/sixth-generation (5G/6G) telecommunication, whileτf of most low-εr microwave dielectric ceramics is relatively negative. In this work, the first low-εr Ga-based ceramic SrGa12O19 with an anomalous positive τf was reported, and the causes of the positive τf, intrinsic polarization, and loss mechanism were systematically studied. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the SrGa12O19 ceramic formed a pure hexagonal magnetoplumbite structure with spinel blocks and rock-salt blocks stacked along the crystallographic c-axis. When sintered at 1430 °C, it possessed the optimal microwave dielectric properties of a low εr of 14.46, high Q×f of 64,705 GHz, and exceptional positive τf of +55.7 ppm/°C, along with a low linear thermal expansion coefficient (αL) of 11.617 ppm/°C. The large positive deviation between εr and εr(C–M) of 45.31% resulted from the rattling effect of atoms in the rock-salt block. The unique positive τf (+55.7 ppm/°C) was governed by the rattling effect, resulting in a positive ταm (the temperature coefficient of ion polarizability) of 8.489 ppm/°C and a large negative temperature coefficient of permittivity (τε) of −132.864 ppm/°C. Phillips–Vechten–Levine (P–V–L) chemical bond theory revealed greater contributions of the spinel block to bond ionicity (fi, 52.95%), permittivity (ε, 55.15%), bond energy (E, 56.87%), and lattice energy (U, 74.88%) than those of the rock-salt block. The intrinsic dielectric properties were analyzed using infrared (IR) reflectivity spectra. The favorable performance of the SrGa12O19 ceramic indicated that it is a novel τf compensator. This selection of compounds with different structural layer combinations provides a new idea for exploring excellent microwave dielectric ceramics.

Recently, fluoride ceramics have gained much interest because of their low permittivities and high Q×f values at microwave frequencies, coupled with relatively low sintering temperatures. In this paper, we have explored the effects of the particle-size and O contamination of LiF raw material, sintering/annealing atmosphere on the mechanosynthesis, structural stability, and microwave dielectric properties of BaLiF 3 ceramic. Using a fine LiF raw material would facilitate the mechanical synthesis of BaLiF 3 , being densified at lower temperatures than the coarse one. A high concentration of oxygen contamination in LiF raw material and partial pressure of O 2 in the sintering atmosphere would lead to the formation of BaF 2 due to the instability of the fluoride perovskite with an increase in the concentration of F-vacancies caused by the partial oxidization during the sintering at high temperature (850 °C/2h). The oxidization of fluoride perovskite preferably occurs at the surface and grain boundaries via O diffusion, which reduces the Q×f value from 83175 to 70228 GHz with little change in ε r (∼11) and τ f values (∼-71 ppm/°C). [ABSTRACT FROM AUTHOR]

xSrTiO 3 -(1-x)SmAlO 3 (ST-SA) (x = 0.4, 0.5, 0.6) microwave dielectric ceramics were prepared by solid-state reaction method and the microwave dielectric properties (ε r , Q × f , τ f) were studied. The 0.4ST-0.6SA component with better Q × f and τ f was selected and the effects of different ywt % Ga 2 O 3 (y = 0.5, 1.0, 1.5, 2.0, 2.5) doping on the phase structure, microstructure, and microwave dielectric properties of ceramics were investigated. X-ray diffraction analysis showed that Ga3+ mainly replaced Ti4+ site when y ≤ 0.5, and when y > 0.5, Ga3+ start to replace Al3+ site. The best grain uniformity of the ceramics was observed at y = 2.0 by scanning electron microscopy testing. Raman spectroscopy shows that the stability of the oxygen octahedron is improved after Ga 2 O 3 doping with increased Q × f value. The change of Ga 2 O 3 doping amount also affects the dielectric properties of ST-SA ceramics. The optimum Q × f value of the ceramic is improved by about 50% from 10,278 GHz (7.465 GHz, 0.4ST-0.6SA) to 15,712 GHz (6.950 GHz, 0.4ST-0.6SA-2.0 wt% Ga 2 O 3) with improved dielectric properties (ε r = 36.14， τ f = 4.17 ppm/°C). [ABSTRACT FROM AUTHOR]

A solid-state sintering process is used to fabricate Li 4 Mg 2 SbO 6 F oxyfluoride ceramics. The sintering behavior, phase structure as well as microwave dielectric performances of Li 4 Mg 2 SbO 6 F sintered bodies were studied. The phase transformation from cubic to orthorhombic occurred for Li 4 Mg 2 SbO 6 F ceramics sintered above 750 °C. The values of ɛ r, Q × f and τ f for Li 4 Mg 2 SbO 6 F ceramics were closely related to density, and configurational entropy caused by the phase transformation. The perfect microwave dielectric performances (ɛ r = 12.6, Q × f = 59,000 GHz (at 11.3 GHz), τ f = −37.0 ppm/K) could be acquired in Li 4 Mg 2 SbO 6 F ceramics following densification at 750 °C. A cylindrical dielectric resonator antenna was fabricated from the 0.15Li 4 Mg 2 SbO 6 F-0.85Li 2 SnO 3 composite ceramics with close zero τ f , which showed good performances. [ABSTRACT FROM AUTHOR]

SrLaAlO 4 -based ceramics have attracted intense interest due to their high quality factor (Qf) at high frequency. However, the poor resonant frequency temperature stability (τ f) limits their practical applications. Therefore, obtaining near-zero τ f while guaranteeing high Qf values is challenging. (Zn 0.5 Ti 0.5)3+ is utilized in Sr 0.6 Ca 0.4 LaAlO 4 ceramics to improve the τ f value effectively. The relationship between the structural features and microwave dielectric properties of Sr 0.6 Ca 0.4 LaAl 1- x (Zn 0.5 Ti 0.5) x O 4 (x = 0–0.5) ceramics has been systematically investigated by XRD, Rietveld refinement, SEM, Raman spectroscopy, TEM and P–V-L theory. XRD and Raman spectroscopy reveal the effect of (Zn 0.5 Ti 0.5)3+ substitution on the evolution of the crystal structure. According to the chemical bond theory, (Zn 0.5 Ti 0.5)3+ substitution leads to the increase of the dielectric constant, which is related to the increase of the average bond ionicity, with the La–O bond contributing predominantly to the bond ionicity. The variation of the Qf values can be attributed to the densification of the ceramics, the lattice energy of the Al/Zn/Ti–O bond, and the FWHM. The τ f value is strongly affected by the coefficient of thermal expansion of the lattice and the Al/Zn/Ti–O bond valence. It is noteworthy that excellent microwave dielectric properties are obtained for Sr 0.6 Ca 0.4 LaAl 1- x (Zn 0.5 Ti 0.5) x O 4 ceramics at x = 0.4: ε r = 21.62, Qf = 87,700 GHz (at 7.23 GHz), and τ f = −1.81 ppm/°C. The above work provides deeper insights into establishing the relationship between the K 2 NiF 4 -type crystal structure and dielectric properties from the perspective of chemical bond. [ABSTRACT FROM AUTHOR]

In pursuit of the objective of implementing fifth-generation communication technology, a LiMg 2 P 3 O 10 microwave dielectric ceramic was developed in this study, and an ultra-wideband dielectric resonant antenna was fabricated. Rietveld refinement confirmed that the monoclinic crystal structure of LiMg 2 P 3 O 10 ceramics is constituted of MgO 6 octahedral chains and shared angle PO 4 tetrahedra. The impact of chemical bond characteristics on properties was explored through P-V-L theory. The primary contributions to the intrinsic properties were investigated through infrared spectroscopy. The LiMg 2 P 3 O 10 ceramics sintered at 830 °C were found to have the best microwave dielectric properties (ε r = 6.16, Q × f = 33,573 GHz (at 15.538 GHz), and τ f = −35.6 ppm/°C). A novel ultra-wideband dielectric resonant antenna with 53.7 % relative bandwidth, 6.53 dBi maximum gain and 81.7 % radiation efficiency was designed and fabricated. Its wide ultra-wideband characteristics makes it suitable for signal transmission in modern wireless communication systems. [ABSTRACT FROM AUTHOR]

This study addresses the challenge posed by the high sintering temperature (>850 °C) required for current high-performance BaZnP 2 O 7 -based ceramics by investigating the substitution of V5+ at the P-site in BaZnP 2 O 7 ceramic. The objective was to lower the sintering temperature to below 850 °C while preserving the high-quality characteristics of the ceramics. Results reveal that the solubility of V5+ in BaZnP 2 O 7 ceramics is limited, and secondary phases such as BaZn 2 (PO 4) 2 and Ba 3 V 2 O 3 (PO 4) 3 were formed when the concentration of V5+ exceeds 0.005. The substitution of V5+ for P5+ effectively reduces the sintering temperature of BaZnP 2 O 7 ceramics from 840 (at x = 0) to 680 °C (at x = 0.10). The dielectric constant (ε r) of BaZn(P 1- x V x) 2 O 7 ceramics is primarily influenced by porosity and the presence of secondary phases. The losses due to anharmonic vibrations in BaZn(P 1- x V x) 2 O 7 ceramics were effectively reduced, leading to an increase in Q × f to ∼70,000 GHz at x = 0.005. The temperature coefficient of resonant frequency (τ f) is mainly affected by bond energy (E) and the content of the Ba 3 V 2 O 3 (PO 4) 3 phase. Ultimately, the BaZn(P 0.995 V 0.005) 2 O 7 ceramic sintered at 820 °C for 4 h exhibited the optimal microwave dielectric properties: ε r = 8.24, Q × f = 75,419 GHz, and τ f = −34.76 ppm/°C. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis and characterization of Ca 0.6 Sr 0.4-x Ba x ZrO 3 (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, Ca 0.612 Sr 0.388 ZrO 3 (CSZ), across the entire range of x values. It is evident that the Ca 0.6 Sr 0.39 Ba 0.01 ZrO 3 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 Ca 0.612 Sr 0.388 ZrO 3 ceramics, and the impedance curves clearly showed effects on the electrical properties. [ABSTRACT FROM AUTHOR]

Dense Sm 2- x Ce x O 3+ x /2 (x = 0.10−0.25) ceramics were obtained by the solid-state method. Main-phase Sm 2 O 3 with monoclinic structure and a small amount of fluorite-structured CeO 2 were achieved. As the x value increased, the τ f significantly reduced from 18.8 ± 2.0 ppm/°C to −20.3 ± 2.0 ppm/°C and the Q × f enhanced from 21,382 ± 300–32,927 ± 300 GHz. The τ f variating from positive to negative was related to the increasing temperature coefficient of ion polarizability (τ αm) from 20.6 ppm/°C to 27.9 ppm/°C. The rise in Q × f was attributed to the reduced AC conductivity resulting from the decreasing oxygen vacancy concentration. The addition of Ce could effectively inhibit the decomposition of Sm 2 O 3 ceramics in atmospheric condition. Notably, the Sm 1.80 Ce 0.20 O 3.10 ceramic sintered at 1475 °C demonstrated optimal microwave dielectric properties of ε r = 19.2 ± 0.2, Q × f = 28,033 ± 300 GHz, and τ f = 1.8 ± 2.0 ppm/°C. [ABSTRACT FROM AUTHOR]

The novel spinel Li 2 Zn 6 MgTi 6 O 20 ceramic with high configuration entropy was synthesized using the traditional solid-state method. Analysis from X–ray diffraction, transmission electron microscope, and Raman spectra demonstrates a disordered state in Li 2 Zn 6 MgTi 6 O 20 (Fd -3 m). This dense ceramic exhibits excellent microwave dielectric properties at 1240 °C: ε r = 18.01 ± 0.2, Q × f = 98,450 ± 3,000 GHz (at 9.17 GHz), and τ f = −38 ± 3.6 ppm/°C. Further studies combining bond valence and P–V–L theory reveal that Ti4+ significantly influences the ε r of Li 2 Zn 6 MgTi 6 O 20 ceramic, while the Ti4+ polarizability is underestimated by 10.6%, resulting in the ԑ r higher than the ԑ th. The solid solution leads to structural disorder and high configuration entropy, driving each bond to contribute almost equally to the bond energy. This structural feature promotes a favorable and stable microstructure, enhancing the microwave dielectric and sintering properties synergistically. Furthermore, the τ f is optimized by composites (4.5 ppm/°C). [ABSTRACT FROM AUTHOR]

A novel type of Li 3 NbO 4 –Li 2 TiO 3 - x MgO (LLM x , x = 1–5) ceramics were prepared using the solid-state reaction method. When the sintering temperature is between 1180 °C and 1300 °C, the solid solution ceramics with cubic rock salt structure are obtained. As the MgO content increases, the ε r value decreases, the τ f value is basically constant, and Q×f exhibits ideal dielectric properties at x = 4 (ε r = 15.26, Q×f = 119,456 GHz (f = 9.97 GHz), τ f = −35.9 ppm/°C). The Raman spectrum analysis was used to examine and understand the vibration mode and intrinsic mechanism of dielectric properties in ceramics. Additionally, a dielectric resonant antenna based on LLM 4 ceramic is fabricated with a resonant frequency of 7.23 GHz (|S 11 | = −45.6 dB), a higher gain and broadband width of 501 MHz. [ABSTRACT FROM AUTHOR]

The well-densified CaREAlO 4 (RE = Eu, Ho, Er, Yb) microwave dielectric ceramics with the K 2 NiF 4 structure are fabricated at 1360–1500 °C. Crystal structures were investigated via XRD and HRTEM, and no phase transition occurred. The ceramics exhibit low ε r of 17.9–19.3 and relatively high Q × f values of 25,110 - 48,310 GHz, and tunable τ f values ranging from −1.1 ppm/°C to +18.4 ppm/°C and then to −20.4 ppm/°C. The variations in ε r and τ f were ascribed to the mutual effects of rattling RE3+ and compressed Ca2+ characterized by bond valence theory and temperature coefficient of ion polarizability (τ αm). The Q×f values of CaREAlO 4 ceramics positively correlate with structure stability and lattice energy, the main intrinsic factors affecting Q×f. [ABSTRACT FROM AUTHOR]

The microwave dielectric properties of NdTi(0.5-x)GexMo0.5O4 ceramics were examined using densification and X-ray diffraction (XRD) patterns. As x increased from 0 to 0.05, the unit cell volume decreased, indicating that Ge4+ ions were incorporated within Ti4+ ions. After sintering at 1425 °C for 4 h, Nd(Ti0.49Ge0.01Mo0.5)O4 ceramics achieved a maximum relative density of 98.9%. The unloaded quality factor (Qu × f) of the NdTi0.49Ge0.01Mo0.5O4 ceramic sintered at 1425 ℃ for 4 h was 33,400 GHz (at 17.6 GHz). Additionally, this ceramic exhibited a dielectric constant (εr) of 17.6 and the obtained temperature coefficient of resonant frequency (τf) was-30.8 ppm/℃. In addition, this ceramic was used as a substrate for slot antenna liquid sensor application. We demonstrated how to improve the measurement results as well as the methodology for obtaining the results. As the water content in acetone increased from 0 to 100%, the measured resonant frequencies shifted from 2.6 to 2.0 GHz. [ABSTRACT FROM AUTHOR]

This study introduced a novel low-loss tungstate ceramic, La 7 Nb 3 W 4 O 30 (LNWO), synthesized using the solid-state techniques. The structural analysis of the La 7 Nb 3 W 4 O 30 ceramic material, utilizing X-ray diffraction (XRD) patterns and followed by detailed structural refinement, validated its rhombohedral structure. Transmission electron microscopy (TEM) was utilized to confirm the ordered layer arrangement characteristic of the rhombohedral structure. The internal structure was characterized by scanning electron microscopy (SEM), with the sample's relative density reaching 97.5 %. The correlation between the full width at half maximum (FWHM) of the Raman matrix at 901 cm−1 corresponding to the symmetric bending mode vibrations of WO 5 and the Q × f value was discussed. Furthermore, the main factors affecting the dielectric constant, including density, bond valence, secondary phases, and variations in porosity, were analyzed. Encouragingly, the ceramic showed significant microwave dielectric properties when it was sintered at 1425 °C (ε r = 23.68, Q × f = 26,687 GHz (f = 7.2 GHz), τ f = −35.2 ppm/°C). [ABSTRACT FROM AUTHOR]

The traditional solid-state sintering method was employed to prepare Li 3 Ba 2 Ln 3 (MoO 4) 8 (Ln = Gd, Tm) ceramics, and the impact of firing temperature on the structure, microstructure and microwave dielectric properties of the novel molybdate Li 3 Ba 2 Ln 3 (MoO 4) 8 (Ln = Gd, Tm) ceramics was examined. XRD and Rietveld refinement outcomes validate the monoclinic system with the C2 / c space group for Li 3 Ba 2 Ln 3 (MoO 4) 8 (Ln = Gd, Tm). For the Li 3 Ba 2 Gd 3 (MoO 4) 8 ceramic sintered at 800 °C, a ε r is 9.42, a Q × f is 16,988 GHz, and a τ f is 4.57 ppm/°C. The Li 3 Ba 2 Tm 3 (MoO 4) 8 ceramic sintered at 800 °C has a ε r of 9.74, a Q × f of 25,401 GHz, and a τ f of 1.08 ppm/°C. XRD and EDS analyses prove the good chemical compatibility of the co-sintered Li 3 Ba 2 Gd 3 (MoO 4) 8 ceramic with the Ag electrode. Therefore, the Li 3 Ba 2 Gd 3 (MoO 4) 8 ceramic is suitable candidate material for LTCC applications. [ABSTRACT FROM AUTHOR]

Novel ZnV 2 O 6 ceramic was synthesized using the solid-state process. A single monoclinic crystalline phase with a space group C2 / m was detected at the sintering temperatures ranging from 580 to 670 °C. The correlations between the chemical bond parameters and microwave dielectric properties were analyzed using the P-V-L bond theory. The full width at half maximum (FWHM) of the most intense Raman peak at 914 cm–1 is inversely proportional to the Q × f value. The ZnV 2 O 6 ceramic can be well-sintered at 640 °C to exhibit an excellent combination of microwave dielectric properties (ε r =14.6, Q × f =46,000 GHz and τ f =–42 ppm/°C). Additionally, the specimen sintered at 580 °C (ε r =13.2, Q × f =28,000 GHz and τ f =–5.2 ppm/°C) is also suggested for highly thermal-stable applications. Both samples can be used as ultra-low-temperature co-fired ceramics (ULTCCs) for high-frequency applications. [ABSTRACT FROM AUTHOR]

In this study, Ba(Mg 1/3 Ta 2/3)O 3 (BMT) ceramics added with different amounts of CaO–B 2 O 3 –ZnO (CBZ) glass were prepared through the solid-state sintering route. The sintering behavior, microstructure, phase composition and dielectric properties of the BMT ceramics added with CBZ glass were investigated. The addition of CBZ glass decreased the sintering temperature of BMT ceramics by over 300 °C, resulting in a highly dense microstructure without interacting with the main BMT phase. The lower sintering temperature led to small ceramic grains and caused a decrease in the Q × f value. Prolonging the sintering time improved the ordering degree of cations on the B-site in BMT ceramic, leading to an enhancement in the Q × f value. The BMT ceramic added with 0.4 wt% CBZ glass exhibited excellent microwave dielectric properties: ε r = 24.19, Q × f = 115,100 GHz, τ f = 9.84 ppm/°C, after sintering at 1400 °C for 12 h. [ABSTRACT FROM AUTHOR]

Li2(Mg1–xCux)2Mo3O12 (0 ≤x ≤0.1) ceramics were prepared using the conventional solid‐phase method to study the effect of the Cu2+ substitution for Mg2+ on the sintering behavior, crystal structure, and microwave dielectric properties of ceramics. The experimental results show that the substitution of Cu2+ for Mg2+ reduces the sintering temperature of the ceramics to 550°C. X‐ray diffraction patterns show that the introduction of Cu2+ does not produce a new phase, but rather promotes the formation of Li2(Mg1–xCux)2Mo3O12 solid solution. The microwave dielectric properties of the ceramics are influenced by the cell parameters, bond lengths, and structural stability. However, Cu2+ creates oxygen vacancies during sintering, thereby deteriorating the dielectric properties (Q × f decreases). The microwave dielectric properties of Li2(Mg1–xCux)2Mo3O12 ceramics are optimal at a sintering temperature of 550°C and x = 0.02, with εr = 9.17, Q × f = 7960 GHz, and τf = –58.77 ppm/°C. Additionally, these ceramics are compatible with Al electrodes. [ABSTRACT FROM AUTHOR]

Co-substitution of Ce3+ at the A-site and Nb5+ at the B-site by smaller Ca2+ and W6+ in (Ce 1- x Ca x)(Nb 1- x W x)O 4 ceramics drives the structure from monoclinic fergusonite (x = 0.1 - 0.3) to tetragonal scheelite (x = 0.4). Adjusting the A-O and B-O bond characteristics could drastically tune the microwave dielectric properties. The ε r decreased from 20.7 to 16.2, and the negative deviations between ε r and ε r (C-M) resulted from the rattling effect of Nb5+/W6+ cations in the octahedron along the b -axis direction. The τ f varied from negative (−11 ppm/°C at x = 0.1) to positive (+87.8 ppm/°C at x = 0.4), mainly attributed to the rattling effect of Nb5+/W6+. Q×f increased from 21,006 to 45,025 GHz (x = 0.3) and then decreased to 36,563 GHZ (x = 0.4), accompanied by increasing packing fraction and decreasing Raman FWHM. The ceramic at x = 0.15 exhibited the optimum microwave dielectric properties of ε r = 19.7, Q×f = 35,450 GHz, and τ f = 0.8 ppm/°C. [ABSTRACT FROM AUTHOR]

A novel Li 4 AlSbO 6 (LASO) microwave dielectric ceramic with a monoclinic structure and space group C12/c1 was successfully prepared using traditional solid-state methods. When the sintering temperature was 1200 °C, it had excellent microwave dielectric properties, with ε r = 8.2, Q × f = 22,098 GHz, and τ f = −15.53 ppm/°C. Raman spectroscopy analysis showed that the FWHM of the strong peak at 691 cm−1 reflected the variation trend of Q × f value and was opposite to the variation trend of Q × f value. Additionally, the augmentation in the Q × f value can be attributed to a higher relative density. As per the bond valence analysis, ε r is closely connected to the rattling and compressing effects of A-site cations, and the higher ε theo than ε r in Li 4 AlSbO 6 can be attributed to the strong compression effect induced by Li+. Additionally, τ f may be influenced by both the Sb–O bond and relative density. [ABSTRACT FROM AUTHOR]

The present work begins with the investigation of a large number of studies that give the phase diagram of Y–Al–O ternary compounds. Furthermore, the phase compositions of the Y 2 O 3 –Al 2 O 3 system at different temperatures are obtained by high-temperature in situ XRD detection. The constitutive relationships between the lattice properties, grain development, polarizability, internal strain and microwave dielectric properties of the three Y–Al oxides (Y 4 Al 2 O 9 , YAlO 3 , Y 3 Al 5 O 12) are elaborated in detail. As an ideal candidate crystalline material for terahertz wave transmission dielectric devices, yttrium-aluminum-garnet ceramics have a dielectric constant of 11.7 in the real part and a Q × f value of 214,735 GHz at high-frequency band (THz). [ABSTRACT FROM AUTHOR]

This study investigates NaY9Si6O26 ceramics prepared through the solid‐phase method, focusing on their microwave dielectric properties and crystallographic characteristics. X‐ray diffraction analysis reveals a hexagonal crystal structure for NaY9Si6O26 ceramics within the P63/m (176) space group. Rietveld refinement analysis precisely determines the lattice constants as a = b = 9.3423 Å, c = 6.7524 Å, and a unit cell volume of V = 510.3877 Å3. Additionally, Raman spectroscopy unveils a noteworthy correlation between the quality factor and the full width at half maximum of the A1g(O) mode at 878 cm−1. The structural attributes, including lattice fringes and diffraction patterns of hexagonal NaY9Si6O26 ceramics, are elucidated through transmission electron microscopy. Of significance are the microwave dielectric properties of NaY9Si6O26 ceramics sintered at 1465°C, revealing a relative permittivity (εr) of 10.42, an impressive Q × f product of 33 766 GHz (at f = 11.14 GHz), and a temperature coefficient of resonant frequency (τf) of −28.7 ppm/°C. This comprehensive investigation contributes to the understanding of both the structural and microwave dielectric characteristics of NaY9Si6O26 ceramics, with potential applications in advanced electronic devices. [ABSTRACT FROM AUTHOR]

With the emergence of 5G–6G communication technology, the miniaturization and integration of electronic components are crucial. Ba3Ti4Nb4O21 (BTN) ceramics with hexagonal structures have attracted special attention due to their high dielectric constant, which shows greater application potential in communication base stations and dielectric resonators. However, its high sintering temperature and low‐quality factors also greatly limit the application field. In this paper, boric acid (H3BO3) as a dopant, was used to investigate the influence on the structure, microstructure, Raman spectrum, and microwave properties for Ba2.92Cu0.08(Zn1/3Nb2/3)2Ti2Nb4O21 (BCZTN)‐xHB (0.25≤x≤1.25 wt%) ceramics. The results reflected that H3BO3 was an effective additive, which could promote ceramic densification, accelerate grain growth and uniform distribution, and enhance its microwave performance. Among them, high densification was 93.92 ± 0.35%, and the Q × f value ∼16981 ± 340 GHz at x = 0.75, was more than 2∼3 times higher than other BTN‐based ceramics. Superior microwave dielectric properties were achieved for 0.75 wt% H3BO3‐doped BCZTN ceramic sintered at 900°C: εr∼42.35 ± 0.48, Q×f∼16981 ± 340 GHz, and τf∼40.02 ± 1.43 ppm/°C. More encouragingly, BCZTN‐0.75HB ceramic did not chemically react with Ag, which suggested that it had the potential to be a candidate material for low‐temperature co‐fired ceramics base station communication devices. [ABSTRACT FROM AUTHOR]

In garnet phase ceramics Y 2.9 M 0.1 Al 4.9 Si 0.1 O 12 (M = Mg2+, Co2+, Zn2+, Mn2+, Ca2+, Sr2+, Ba2+), rattling effects occur when M = Mg2+, Co2+, Zn2+, Mn2+ ions with smaller ionic radius (<1Å) occupy the dodecahedron lattice lattices. This results in an abnormally high dielectric constant, in contrast to the larger ionic radius (>1 Å) of M = Ca2+, Sr2+ and Ba2+, which deviate from the theoretical values calculated using the Clausius-Mosotti formula according to each ion's polarizability. The optimal microwave dielectric properties for Y 2.9 Mg 0.1 Al 4.9 Si 0.1 O 12 was obtained by sintering at 1575 °C for 5 h (Q × f = 51,382 GHz, ε r = 9.74, and τ f = −30.12 ppm/°C). Additionally, a thermal stable Y 2.9 Mg 0.1 Al 4.9 Si 0.1 O 12 -6 wt%TiO 2 composite ceramic was developed. Based on this composite, a Wifi6E/7 patch antenna operating at 6.3 GHz and a millimeter-wave resonant antenna functioning at 27.1 GHz were designed and validated. This indicates the potential application prospects of garnet ceramics in 5G/6G radio communication technologies. [ABSTRACT FROM AUTHOR]

The present study focuses on the synthesis and characterization of rare-earth titanates, specifically Re 2 TiO 5 (Re La, Nd, Sm), with a particular emphasis on their microwave dielectric properties. The factors influencing the synthesis of La 2 TiO 5 compound through the traditional solid-state method were thoroughly investigated, with a significant finding being the notable impact of moisture absorption in La 2 O 3. The impact of variations in rare-earth cation radii on the structure and dielectric properties was systematically analyzed. Re 2 TiO 5 (Re La, Nd, Sm) ceramics crystallized into an orthorhombic structure with space group Pnam, which was confirmed through Rietveld refinement. The resulting materials demonstrated exceptional microwave dielectric properties characterized by a low permittivity range of 13.72–17.39, high-quality factors ranging from 8331 to 17,795 GHz, and a significantly reduced temperature coefficient of resonance frequency (−33.2∼-12.6 ppm/°C). The correlation between microwave dielectric properties and structural characteristics (including ionic polarizability, packing fraction, and bond valence) was investigated. The exceptional potential of these rare-earth titanates lies in their ability to meet the stringent requirements for low signal transmission delay in wireless communication systems, owing to their advantageous low permittivity within the microwave frequency spectrum. [ABSTRACT FROM AUTHOR]

This study delves into the synthesis and characterization of rare earth germanate La 4 GeO 8 ceramics, employing the solid-phase reaction method, with a focus on their microwave dielectric properties and crystallographic characteristics. The research employs X-ray diffraction (XRD) and transmission electron microscopy (TEM) to ascertain the orthorhombic crystal structure within the Pnma space group. Rietveld refinement analysis precisely determines the lattice constants (a = 18.3006 Å, b = 7.6697 Å, c = 5.8513 Å) and unit cell volume (V = 821.28429 Å3). Raman spectroscopy provides insights into the correlation between the quality factor (Q × f) and the Full Width at Half Maximum (FWHM) of the A g (O) mode at 733 cm⁻1. A notable highlight of the study is the exceptional microwave dielectric performance of La 4 GeO 8 ceramic sintered at 1540 °C, characterized by a relative dielectric constant (ε r) of 13.24, a Q × f product of 47,826 GHz at 10.16 GHz, and a temperature coefficient of frequency (τ f) of −82.3 ppm/°C. This comprehensive investigation offers valuable insights into the structural and microwave dielectric properties of AB-type rare earth germanate La 4 GeO 8 ceramics, underscoring their potential in advanced dielectric material applications. [ABSTRACT FROM AUTHOR]

In this study, we report the effect of Zr4+ doping on the optical energy gap and microwave dielectric properties of rutile TiO2. Rietveld analysis explicitly confirmed that Zr4+ occupies the octahedral site, forming a single-phase tetragonal structure below the solubility limit (x < 0.10). Notably, at x = 0.025, a significant enhancement in Q × fo was observed. This enhancement was attributed to the reduction in dielectric loss, associated with a decrease in oxygen vacancies and a lower concentration of Ti3+ paramagnetic centers. This conclusion was supported by Raman and electron paramagnetic resonance spectroscopy, respectively. The origin of high τf in rutile Ti1−xZrxO2 is explained on the basis of the octahedral distortion/tetragonality ratio, covalency, and bond strength. [ABSTRACT FROM AUTHOR]

Investigating the microwave dielectric properties of ceramics prepared through the conventional solid-state route, such as x[(Mg0.6Zn0.4)0.95Co0.05]1.02TiO3.02-(1−x)Ca0.6(La0.9Y0.1)0.2667TiO3, reveals notable characteristics. [(Mg0.6Zn0.4)0.95Co0.05]1.02TiO3.02 shows a permittivity (εr) of approximately 20, a high quality factor (Q × f) ranging between 250,000 and 560,000 GHz, and a temperature coefficient of resonant frequency (τf) of approximately −65 ppm/°C. To enhance the temperature stability, Ca0.6(La0.9Y0.1)0.2667TiO3 featuring a τf value of +374 ppm/°C was incorporated into the [(Mg0.6Zn0.4)0.95Co0.05]1.02TiO3.02 composition. τf demonstrated an increase with rising Ca0.6(La0.9Y0.1)0.2667TiO3 content, reaching zero at x = 0.95. A ceramic composition of 0.95[(Mg0.6Zn0.4)0.95Co0.05]1.02TiO3.02-0.05Ca0.6(La0.9Y0.1)0.2667TiO3, incorporating 3wt.% BaCu(B2O5) as sintering aids, exhibited outstanding microwave dielectric properties: εr~22.5, Q × f~195,000 (at 9 GHz), and τf~0.1ppm/°C, with a sintering temperature at 950 °C. This material is proposed as a prospective candidate for 6G band components and GPS antennas. [ABSTRACT FROM AUTHOR]

This study prepared ultralow electron-loss perovskites with spinel-like structures via a solid-state reaction. The (Mg0.95Co0.05)2(Ti0.95Sn0.05)O4 (MCTS) ceramic exhibited approximate values for ultrahigh quality factor, permittivity, and negative temperature coefficient (τf) of 310,000 GHz, 14.25, and −48.1 ppm/oC, respectively. To bring the τf closer to zero, a trace amount of (Ca0.95Sr0.05)(Ti0.97Sn0.03)O3 (CSTS) perovskite was added to MCTS during ceramic manufacturing. CSTS exhibited a permittivity of 92 and a large positive τf value of 810 ppm/°C. A 0.92MCTS–0.08CSTS hybrid ceramic sintered at 1325°C achieved remarkable microwave dielectric properties of εr ~18.42, Q×f ~ 237,000 GHz and τf ~3.72 ppm/°C. This mixed ceramic has significant potential for applications in manufacturing microwave devices. [ABSTRACT FROM AUTHOR]

This study delves into the microwave dielectric properties of Li2Y9(SiO4)6O2F ceramics, synthesized using the conventional solid-state method. By employing x-ray diffraction analysis and meticulous data refinement across various temperatures, we unequivocally confirm the hexagonal crystal structure of Li2Y9(SiO4)6O2F ceramics. The refined lattice parameters, observed at a sintering temperature of 1275°C, exhibit a = b = 9.33318 Å, c = 6.71725 Å, with a corresponding unit cell volume of V = 506.73529 Å3. In-depth scrutiny of the microstructure of the ceramics' grains using scanning electron microscopy (SEM) reveals an optimal relative density of 96.2%. Subsequently, the study explores the impact of porosity, packing fraction, relative density, and Si-O bond valence (VSi-O) on the microwave dielectric properties of Li2Y9(SiO4)6O2F ceramics. Notably, the Li2Y9(SiO4)6O2F ceramic sintered at 1275°C demonstrates superior performance metrics, boasting an εr value of 14.28, a Q × f product of 16,760 GHz (at f = 9.4 GHz), and a temperature coefficient of frequency (τf) at 3.14 ppm/°C. This comprehensive investigation contributes valuable insights into optimizing the microwave dielectric characteristics of Li2Y9(SiO4)6O2F ceramics for potential applications in advanced electronic devices. [ABSTRACT FROM AUTHOR]

In this work, a silicate ceramic, CaY2Al4SiO12 (CYASO), with a low dielectric constant and low loss was prepared using traditional solid-state methods. X-ray diffraction (XRD) refinement analysis shows that the CYASO material crystallized into a phase with an Ia-3d space group and an impurity peak. The orthogonal cubic structure of the CYASO ceramic was confirmed through transmission electron microscopy (TEM), and the structure exhibited an orderly layered arrangement. The internal microstructure was characterized using scanning electron microscopy (SEM), which showed that the sample's relative density reached 97.8%. We discuss the correlation between the full width at half maximum (FWHM) of the Raman matrix corresponding to the vibration mode of the symmetric bending mode of AlO4 at the Raman shift of 855 cm−1 and the Q × f value. Additionally, the analysis focused on the various factors that influence the dielectric constant, including density, secondary phase, and porosity changes. The ceramics exhibited remarkable microwave dielectric properties (εr = 8.7, Q × f = 34,700 GHz, τf = −35 ppm/°C) when calcined at 1425°C. CYASO ceramic shows great capacity as a microwave dielectric material. [ABSTRACT FROM AUTHOR]