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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 Li 2 BaP 2 O 7 ceramics, synthesized through the solid-state reaction method, exhibit a pure monoclinic phase. Upon sintering at 750 °C, the ceramic achieves a high relative density of 97.3 %, which is indicative of an optimal microstructure conducive to the superior microwave dielectric properties: a ε r of 9.9, a Q × f of 86200 GHz, and a τ f of −95.4 ppm/°C. The variation in relative density is identified as the principal driver of changes in both the ε r and Q × f values for the Li 2 BaP 2 O 7 ceramics. The molecular polarizability is pivotal in determining the ε r of Li 2 BaP 2 O 7 ceramics. The P-V-L theory analysis elucidates that the P-O bond significantly surpasses other chemical bonds in contributing to the ionicity, lattice energy, and bond energy, thereby underscoring its dominance over the three principal microwave dielectric characteristics. Furthermore, Raman spectroscopy data demonstrate that the P-O bond vibration predominantly governs the overall vibrational spectrum. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the mechanical and thermal properties of rare earth sesquioxides A/B/C‐RE2O3 (RE = La to Lu) by using the first‐principles calculation. It is shown that the lattice parameters of RE2O3 generally decrease with the rare earth atomic number owing to the lanthanide contraction. Compared to [REO6] polyhedrons, all [REO7] polyhedrons present the longer RE‐O bonds and the lower energies in spite of different polymorphs. Meanwhile, the elastic moduli show clear increasing tendency from A‐RE2O3 to C‐RE2O3 and from La2O3 to Lu2O3, which may originate from the stronger covalancy or weaker ionicity according to P‐V‐L chemical bond theory. In addition, the theoretical minimum thermal conductivity is predicted in range of 0.57–0.61 W·m1·K−1, 0.68–0.72 W·m−1·K−1, and 0.59–0.73 W·m−1·K−1 for A‐, B‐, and C‐RE2O3, respectively. Further analysis about temperature‐dependent thermal conductivity indicates that the chemical bonds dominate the increasing thermal conductivity with RE elements while the structural complexity determines the difference between three phases. This work provides a comprehensive database on structural, mechanical and thermal properties of RE2O3, but also shields light on the exploration of rare‐earth‐containing oxides with complex structure for potential applications including thermal/environmental barrier coatings. [ABSTRACT FROM AUTHOR]

Mg 3 Ga 2 TiO 8 ceramics were prepared using a solid-phase method. The ceramics sintered at 1440 °C exhibited excellent microwave dielectric properties (ε r = 12.07, Q × f = 89,270 GHz, and τ f = −40.7 ppm/°C). The typical spinel structure of the Mg 3 Ga 2 TiO 8 ceramic was confirmed through Rietveld refinement and Raman spectroscopy. High-resolution transmission electron microscopy indicated local lattice distortion in the Mg 3 Ga 2 TiO 8 ceramics, with a Vickers hardness of 12.53 GPa. The values of ε r and Q × f for the Mg 3 Ga 2 TiO 8 ceramics were affected by the relative density. The theoretical ε r obtained from the C-M equation was lower than the measured ε r , plausibly due to underestimation of the polarizability of the Ti ions. According to the P-V-L theory, Ti2-O1 has the highest f i value, contributing 29.92 % to ε r. The contribution rate of the Ga2-O1 bond to U was 35.76 %, with the greatest impact on Q × f. [ABSTRACT FROM AUTHOR]

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]

Novel spinel-type Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics were prepared by the solid-state method. Rietveld refinement revealed that the Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics possess a cubic spinel structure with the F d 3 ‾ m (227) space group. Raman spectrum analysis indicated that the Q × f and FWHM of ceramics exhibit an inverse relationship. According to the P-V-L theory, the Ti-O bond has the highest percentage of contribution to both of bond ionicity and lattice energy, indicating a significant impact on ε r and Q × f , respectively. The Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics showed the best microwave dielectric properties (ε r = 15.72, Q × f = 69,633 GHz, and τ f = −20 ppm/°C), sintering at an optimum temperature of 1200 °C. Additionally, a dielectric resonance antenna, on the basis of Li 2 Mg 2 Ga 2 Ti 3 O 12 ceramics was designed and simulated. [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]

A solid-state synthesis method was employed to produce (Mg 1-x Mn x) 2 Ti 0.95 Ga 1/15 O 4 (x = 0.06,0.12,0.18, and 0.24), which is intended for use in mobile communications. This involved using a combination of Mg 2 Ti 0.95 Ga 1/15 O 4 and Mn 2 Ti 0.95 Ga 1/15 O 4 solid solutions. By substituting Mg2+ and Mn2+, the resulting material exhibited an improved Q × f value and achieved densification (ρ re = 97.62 %) at a lower sintering temperature compared to the sintering temperature required for Mg 2 TiO 4 , which is 1450 °C. After sintering at 1350 °C for 4 h, (Mg 0.94 Mn 0.06) 2 Ti 0.95 Ga 1/15 O 4 ceramic showed optimal dielectric properties (ε r = 14.59, Q × f = 263,953 GHz, τ f = −61.86 ppm/°C). To delve deeper into the inherent mechanisms of the ceramic's microwave dielectric properties, a thorough analysis was conducted based on the P–V-L theory. Additionally, XRD analysis revealed a minor secondary phase (Mg 1-x Mn x Ti 0.95 Ga 1/15 O 3) that deteriorated loss characteristics. SEM provided a comprehensive view of the grains' morphologies, giving crucial insights into the microstructure, while Raman spectroscopy explored into the intricate influence of lattice vibrations on the microwave dielectric properties of the ceramics. [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]

In this study, Ce2[Zr1−x(Ba1/3Nb2/3)x]3(MoO4)9 (0.02 ≤ x ≤ 0.1, CZ1−xNx) ceramics were sintered at 600 °C and 700 °C using the traditional solid-state method. An analysis conducted through XRD and Rietveld refinement confirmed that all the CZ1−xNx ceramics displayed a single phase with a trigonal structure (space group R-3c). The observed increases in cell volume with increasing x values indicate the successful substitution of (Ba1/3Nb2/3)4+. The high densification of the synthesized phase was validated by the density and SEM results. Additionally, the P-V-L theory demonstrates a strong correlation between the Ce-O bond and εr, as well as τf, and between the Mo-O bond and Q×f. Notably, the CZ0.98N0.02 ceramics demonstrated superior performance at 675 °C, exhibiting εr = 10.41, Q×f = 53,296 GHz, and τf = −23.45 ppm/°C. Finally, leveraging CZ0.98N0.02 ceramics as substrate materials enabled the design of a patch antenna suitable for the 5G communication band, demonstrating its significant potential in this field.

The single-phase, cubic-structured Ba 3 La(PO 4) 3 ceramics were synthesized using the traditional solid-state reaction method. The ceramic sintered at 1375 °C exhibited a relative density of 95.4 %, indicative of a dense microstructure and excellent sintering characteristics. Furthermore, they displayed remarkable microwave dielectric properties: ε r = 9.54, Q × f = 32820 GHz, and τ f = −43.1 ppm/°C. In addition, the relative density is positively correlated with ε r and Q × f of ceramics. According to the complex chemical bond theory, the ionicity of the Ba/La–O bond has a more significant impact on the ε r , while the lattice energy and bond energy of the P–O bond respectively dominate the Q × f and τ f values. Moreover, the results from Raman spectroscopy indicate that several prominent Raman bands are associated with the vibration of the P–O bond. These findings suggest that Ba 3 La(PO 4) 3 ceramics hold promise for applications in high-frequency microwave communication. [ABSTRACT FROM AUTHOR]

In this study, Ce2[Zr1−x(Ba1/3Nb2/3)x]3(MoO4)9 (0.02 ≤ x ≤ 0.1, CZ1−xNx) ceramics were sintered at 600 °C and 700 °C using the traditional solid-state method. An analysis conducted through XRD and Rietveld refinement confirmed that all the CZ1−xNx ceramics displayed a single phase with a trigonal structure (space group R-3c). The observed increases in cell volume with increasing x values indicate the successful substitution of (Ba1/3Nb2/3)4+. The high densification of the synthesized phase was validated by the density and SEM results. Additionally, the P-V-L theory demonstrates a strong correlation between the Ce-O bond and εr, as well as τf, and between the Mo-O bond and Q×f. Notably, the CZ0.98N0.02 ceramics demonstrated superior performance at 675 °C, exhibiting εr = 10.41, Q×f = 53,296 GHz, and τf = −23.45 ppm/°C. Finally, leveraging CZ0.98N0.02 ceramics as substrate materials enabled the design of a patch antenna suitable for the 5G communication band, demonstrating its significant potential in this field. [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 Ba 3 (ZnB 5 O 10)PO 4 (BZBPO) phosphate ceramic was synthesised using a conventional solid-state technology. The BZBPO ceramic sintered at 850 °C demonstrated exceptional microwave dielectric properties: ε r = 5.88 ± 0.08, Q×f = 52,896 ± 1200 GHz (f 0 = 16.5 GHz) and τ f = 0.34 ± 0.25 ppm/°C. Raman spectroscopy revealed that ε r and Q×f were negatively correlated with the Raman shift and full width at half maximum of the BZBPO ceramic, respectively. Meanwhile, Phillips–Vechten–Levine theory revealed that Q×f was highly correlated with the lattice energy (U b), and τ f was closely related to the bond energy (E b) and the thermal expansion coefficient. Among contribution ratios of individual chemical bonds, the B–O bond mainly contributed to U b , E b and ionicity, proving that the bond dominantly affected the dielectric properties of the BZBPO ceramic. Finally, the BZBPO ceramic was co-fired with silver, demonstrating its potential applicability towards low temperature co-fired ceramic technology. [ABSTRACT FROM AUTHOR]

Ca 2 LaNbO 6 (CLN) ceramics were synthesised using a solid-state reaction process. The CLN ceramics were characterised through X–ray diffraction, transmission electron microscopy, and Rietveld refinement, and it was confirmed that they crystallised into a pure Ca 2 LaNbO 6 phase with a monoclinic structure. The analysis of Raman spectra verified that the ε r exhibited a variation tendency contrary to that of Raman shift near 744 cm−1. The Q×f was highly dependent on the lattice energy (U b), full width at half-maximum, and packing fraction, and the τ f was mainly affected by bond energy (E b). Furthermore, P–V–L analysis indicated that both the ionicity (f i) and U b depended heavily on the Nb–O bond, whereas E b was dominated by the Ca–O bond. The CLN ceramics sintered at 1175 °C exhibited favourable microwave dielectric properties, including ε r of 21.92 ± 0.077, Q×f of 63,207 ± 500 GHz (f 0 = 8.2 GHz), and τ f of − 8.06 ± 0.41 ppm/°C. [ABSTRACT FROM AUTHOR]

Li 5 Mg 3 Ti 2 O 9 F (LMTOF) ceramic was successfully synthesized using the solid-state reaction method at a temperature of 925 °C. XRD analysis revealed the presence of a unique cubic structure, resulting in the formation of a solid solution of Li 5 Mg 3 Ti 2 O 9 F. Notably, a significant correlation was observed between the ions polarization and the ε r of the LMTOF ceramic. Furthermore, the impact of sintering temperature on the ε r and Q × f value of the ceramic was primarily evidenced by changes in the sintered density. Applying the P–V-L theory, computational results highlighted the crucial role played by the ionicity of Mg–O/F and Ti–O/F in determining the behavior of the LMTOF ceramic. Particularly, the lattice energy associated with the Ti–O/F bond exerted a predominant influence on the Q × f value, while the bond energy of Li–O/F exhibited a greater impact on the τ f. Additionally, insightful details regarding the lattice vibrations of the ceramic were obtained through Raman spectroscopy. Impressively, the ceramic sintered at 925 °C exhibited exceptional microwave dielectric performance, demonstrating an ε r of 14.8, a Q × f value of 98,500 GHz, and a τ f of −15.6 ppm/°C. These outcomes underscore the significant potential of LMTOF ceramic for advancements in the LTCC field. [ABSTRACT FROM AUTHOR]

In this study, Ba 1- x Sr x ZnP 2 O 7 (0 ≤ x ≤ 0.1) ceramics were synthesized at 875–950 °C. The X-ray diffraction and SEM test revealed that Ba 1- x Sr x ZnP 2 O 7 (0 ≤ x ≤ 0.1) ceramics formed a single phase with a P-1 triclinic structure. Moreover, a moderate substitution of Sr2+ is conducive to grain growth and pore reduction. The ε r value was primarily affected by the average bond ionicity (A f i) and porosity, while the unit molecule polarizability contribution was insignificant. The Q × f value was closely related to the packing fraction, U total , and FWHM value of the strongest peak with a wavelength of approximately 1050 cm−1 in Raman spectra. Additionally, the P–O bond significantly influenced the bond ionicity and lattice energy. The Ba 0.92 Sr 0.08 ZnP 2 O 7 ceramic sintered at 925 °C for 4 h exhibits satisfactory microwave performance: ε r = 8.26 ± 0.06, Q × f = 61,677 ± 1781 GHz, τ f = −18.34 ± 0.21 ppm/°C. [ABSTRACT FROM AUTHOR]

Novel glass-free low-temperature cofiring NaCaLn(MoO 4) 3 (Ln = Nd, Sm) ceramics were prepared by a conventional solid-state reaction method, and their sintering characteristics, phase composition, micro-morphology and microwave dielectric properties were comprehensively investigated. The pure tetragonal scheelite structure of NaCaLn(MoO 4) 3 (Ln = Nd, Sm) ceramics were disclosed by the XRD patterns. The extremely dense micro-morphology was revealed in the SEM images, which corresponds to the density measurements results. Those results showed that the change of ε r values is closely related to relative density and molecular polarizability. The change in Q × ƒ value are considered influenced by both grain size and packing fraction. In addition, the largest contribution of Mo–O bonds to the Q × ƒ of NaCaLn(MoO 4) 3 (Ln = Nd, Sm) ceramics was revealed by P–V–L theory. The best dielectric properties were obtained at 850 °C and 875 °C for NaCaNd(MoO 4) 3 and NaCaSm(MoO 4) 3 , respectively: ε r = 11.06, Q × ƒ = 58,442 GHz, τ ƒ = −37.7 ppm/°C and ε r = 11.02, Q × ƒ = 47,190 GHz, τ ƒ = −43.8 ppm/°C. Furthermore, the good compatibility of these two ceramics with silver powder indicated that they have potential for LTCC applications. [ABSTRACT FROM AUTHOR]

The effect of Li 2 O substitution on the sintering behavior, lattice structure, microstructure, and microwave dielectric properties of ZnO–B 2 O 3 –Bi 2 O 3 glass-ceramics was studied by various amounts of Li 2 O to substitute ZnO. The substitution of Li 2 O decreases the glass network connectivity and thus decreases the sintering temperature of the glass. In the sintered glass-ceramics, the substitution of 0.2 mol % Li 2 O leads to the most significant lattice activation resulting in the glass-ceramic exhibiting the smallest cell volume of Zn 3 B 2 O 6 crystal and the microstructure with fine and uniform grains. The P–V-L theory is innovatively applied to glass-ceramic materials to characterize the variation in bond characteristics caused by lattice activation and it indicates that the 0.2 mol % Li 2 O substitution decreases the Zn–O bond ionicity and increases the lattice energy of the B–O bond, in the Zn 3 B 2 O 6 crystalline phase. The refinement of microstructure and the optimization of bond characteristics improve the microwave dielectric properties of glass-ceramics. The glass-ceramic with 0.2 mol % Li 2 O substitution sintered at 620 °C for 5 h exhibits excellent microwave dielectric properties of ε r ∼5.05, Q×f ∼15,383 GHz, τ f ∼ −6 ppm/°C and good chemical compatibility with Ag or Al electrodes, which is a favorable candidate for application in ULTCC substrate materials. [ABSTRACT FROM AUTHOR]

The La 2 Sn 2 O 7 ceramic was synthesized using the solid−phase reaction method. The crystal structure, sintering characteristics, and microwave dielectric properties of the La 2 Sn 2 O 7 ceramics were studied. XRD analysis shows that La 2 Sn 2 O 7 ceramics possess a pyrochlore structure with a space group of F d 3 ¯ m. As the sintering temperature increases, the ε r and relative density show the same trend of change. The Q × f of ceramics has a strong correlation with the packing fraction. The P−V−L theory shows that La−O and Sn−O bonds have certain effects on the ε r and Q × f. The intrinsic dielectric properties of ceramics were analyzed using infrared reflection spectra. At 1350 °C, La 2 Sn 2 O 7 ceramic obtained the largest relative density and optimum microwave dielectric properties (ε r = 15.65, Q × f = 73,804 GHz and τ f = −18.58 ppm/°C). [ABSTRACT FROM AUTHOR]

Low-temperature sintered La 2−x Y x Mo 2 O 9 ceramics (x = 0–0.12) were synthesized by solid-state method. XRD analysis confirmed pure La 2 Mo 2 O 9 with a cubic structure (space group P 21 3). Sintering at 925 °C resulted in La 2 Mo 2 O 9 ceramic with favorable microwave dielectric properties: ε r = 17.8, Q × f = 24300 GHz, τ f = −35.1 ppm/°C. Notably, adding Y3+ greatly improved Q × f and τ f. Sintering La 1.88 Y 0.12 Mo 2 O 9 at 900 °C significantly enhanced microwave dielectric properties: ε r = 17.4, Q × f = 34100 GHz, τ f = −5.5 ppm/°C. ε r was primarily influenced by ionic polarizability, while Q × f correlated positively with packing fraction. Analysis based on P-V-L theory showed that increased ionicity, lattice energy, and bond energy led to higher ε r , Q × f , and τ f values. Raman spectroscopy revealed that most observed peaks were associated with Mo-O bond vibrations. These findings highlight La 2−x Y x Mo 2 O 9 ceramics as promising candidates for LTCC materials. [ABSTRACT FROM AUTHOR]

In this work, two novel CaASbWO 8 (A = Gd, La; named CGSWO and CLSWO) microwave dielectric ceramics were synthesized by a classical solid-state method. Remarkably, the outstanding microwave dielectric properties (ε r = 12.97, Q×f = 45,034 GHz, and τ f = −16.29 ppm/°C) were achieved for CGSWO ceramics sintered at 1440 °C, and CLSWO ceramics sintered at 1300 °C possessed the excellent microwave dielectric properties of ε r = 9.89, Q×f = 61,326 GHz, and τ f = 0.55 ppm/°C. Bond valence, ionic polarizability, Raman spectroscopy and Phillips–Vechten–Levine (P-V-L) theory were used to study the internal lattice vibration and chemical bonds in detail, and the dielectric properties were explored from the internal factors. In comparison to the ε r , the ε theo of CGSWO was found to be consistently underestimated, whereas CLSWO exhibited a contrasting pattern. This discrepancy was primarily attributed to the rattling and compressed effects of A-site cation. According to the analysis of P-V-L theory, W-O bond played an important role in regulating the Q×f value. Moreover, the τ f values of CGSWO and CLSWO ceramics were opposite, which provided an opportunity to manufacture microwave ceramic devices with good temperature stability. [ABSTRACT FROM AUTHOR]

In this work, tetragonal K 2 NiF 4 structured SrPrBO 4 (B = Ga, Al) ceramics with I 4/ mmm space group were synthesized via the conventional solid-phase method. High relative density (>95 %) and excellent microwave dielectric properties of ε r = 18.15, Q × f = 36,643 GHz, τ f = −20.20 ppm/°C for SrPrAlO 4 , and ε r = 22.02, Q × f = 27,475 GHz, τ f = +19.11 ppm/°C for SrPrGaO 4 were obtained when sintered at 1500 °C and 1375 °C, respectively. Analyses of the bond valences show that the ε r and τ f values are closely related to the rattling and compressing effects of the A-site cation. The strong compressed effect of Sr2+ in SrPrAlO 4 leads to its ε r value less than the ε r(C-M) ; while, the strong rattling effect of Pr3+ in SrPrGaO 4 leads to its ε r value higher than the ε r(C-M) , and thus to a positive τ f. The Al/Ga–O bonds play a crucial role in the influence of the dielectric loss according to the P–V–L chemical bonding theory analysis. The E dc of SrPrAlO 4 (0.99 eV) and SrPrGaO 4 (0.52 eV) indicates that the formation mechanisms of oxygen vacancies in both ceramics are different. [ABSTRACT FROM AUTHOR]

ZnCu 2 Nb 2 O 8 (ZCN) ceramics were prepared by solid-state reaction technology for investigating the influences of different sintering temperatures (S.T.) on crystal structure, microscopic morphology, and microwave dielectric properties. The characterization results of X-ray diffraction (XRD), Rietveld refinement, and transmission electron microscope (TEM) identify formation of ZnCu 2 Nb 2 O 8 phase with triclinic structure and P 1 ‾ space group. Scanning electron microscopy (SEM) demonstrates that proper sintering temperature can promote growth of grains, revealing the maximum relative density of 98.9% for ZCN ceramics sintered at 920 °C. Inverse correlation is observed between dielectric constant (ε r) and Raman shift of A 1g (O) near 805 cm−1. The relative density, lattice energy (U b) and full width at half maximum (FWHM) are correlated with the quality factor (Q × f) of ZCN ceramics. Based on P–V-L theory, it is confirmed that Nb–O bond plays dominant role in ionicity, lattice energy, and bond energy, which has significant impact on the dielectric properties than other bonds. Notably, the ZCN ceramics by sintering at 920 °C, present optimal microwave dielectric properties: ε r = 18.56, Q × f = 47,776 GHz, and τ f = −16.3 ppm/°C. Furthermore, The co-firing ZCN ceramics with Ag demonstrates good compatibility, highlighting the potential candidacy of ZCN ceramic as low temperature co-fired ceramic (LTCC). [ABSTRACT FROM AUTHOR]

In order to develop novel lightweight low-cost microwave dielectric ceramics (MDCs), middle- ε r Na 2 Ti 6 O 13 ceramics were prepared by a traditional solid-state reaction method and the sintering behavior and microwave dielectric properties ((MDPs) were investigated. The detailed structural parameters of the Na 2 Ti 6 O 13 ceramics were obtained by X-ray diffraction and Rietveld refinement, and the chemical bond characteristics of the structures were further studied using Raman spectroscopy. The relative density of the ceramics and scanning electron microscopy (SEM) images show that density and porosity are important factors affecting the dielectric properties of the samples. Based on the acquired Raman spectra and complex chemical bond theory (P–V–L theory), the chemical bond properties were calculated and analyzed, and the effects of intrinsic factors on the MDPs were investigated. The MDPs of Na 2 Ti 6 O 13 ceramic sintered at 1025 °C were as follows: ε r = 34.3, Q×f = 33660 GHz, and τ f = 40.3 ppm/°C. [ABSTRACT FROM AUTHOR]

TiSnNbTaGa 2 O 12 (TSNTGO) high–entropy dielectric ceramic was successful synthesized using the solid-state reaction method. X–ray diffraction (XRD), Rietveld refinement and transmission electron microscopy (TEM) were used to verify that all samples have rutile structure of P42–mnm space group. The analysis of Raman spectra proved that the ε r exhibited a contrary changing trend as that of Raman shift near 822 cm−1, and the same similar relationship occurred between Q×f values and full width at half maximum (FWHM). The exploration of complex chemical bonding theory (P–V–L theory) for TSNTGO ceramics suggested that the bond ionicity played a dominant role in ε r , while Q×f and τ f were primarily determined by lattice energy and bond energy, respectively. Notably, the TSNTGO ceramics sintered at 1275 ℃ demonstrated optimal microwave dielectric properties of ε r = 33.62 ± 0.03, Q×f = 51,832 ± 1000 GHz (f 0 = 6.4 GHz), and τ f = –0.38 ± 0.16 ppm/℃. [ABSTRACT FROM AUTHOR]

Dense microwave dielectric ceramics of Sr1–xCaxTm2O4 (x = 0.025–0.300) were fabricated via the conventional solid-state reaction method. Systematical investigations on the impact of Ca2+ on their microstructures, sintering behaviors, and microwave dielectric properties were detailly conducted. The combined XRD data and subsequent refinement demonstrated that all samples exhibited structural conformity with SrTm2O4 and belonged to Pnam space group. Calculations were executed to illustrate the evolution of performance-related chemical bonding parameters associated with Ca2+ on the basis of the PVL theory. High density, lattice energy and narrow full width at half maximum of Raman modes contribute to a performance boost of around 14%. Excellent dielectric properties of Sr0.95Ca0.05Tm2O4, including relative permittivity of 15.97, quality factor of 47,142 GHz, and temperature coefficient of resonant frequency of −24.65 × 10−6 °C−1. Furthermore, Sr0.95Ca0.05Tm2O4 ceramics were designed as rectangular dielectric resonator antennas with 388 MHz bandwidth at the center frequency of 6.525 GHz, along with high simulated radiation efficiency (≥90%) and realized gain (5.80–6.47 dBi), which suggests their considerable potential in 5G communication applications.

This paper presents a study on the microwave dielectric properties of K 2 Bi(PO 4)(MoO 4) (KBPM) ceramics prepared through the solid-state method. XRD refinement analysis confirmed the presence of the orthorhombic crystal structure of the ceramics, belonging to space group Ibca (#73), with only the K 2 Bi(PO 4)(MoO 4) phase observed. The ceramic sintered at 625 °C exhibited the most compact structure and demonstrated excellent microwave dielectric properties: ε r = 8.37, Q × f = 42,500 GHz, and τ f = −78.2 ppm/°C. The measured value of ε r closely matched the theoretical value, indicating a strong correlation between polarization and the ε r. The Q × f value was found to be influenced by the packing fraction, while the τ f value showed an inverse relationship with the Mo–O bond valence. Analysis based on the P–V-L theory revealed the interconnected nature of ionicity, lattice energy, bond energy, and the ε r , Q × f , and τ f of the ceramics. Raman spectroscopy provided valuable insights into the lattice vibrations of the ceramics. Additionally, the KBPM ceramics were found to possess favorable chemical compatibility with silver, suggesting their potential application as ultra-low-temperature co-fired ceramics. [ABSTRACT FROM AUTHOR]

Low-fired Li 3 VO 4 ceramics were fabricated and their sintering characteristics, intrinsic structure of the crystal, and microwave dielectric performances were discussed. After the Rietveld refinements, all samples showed the single orthorhombic Li 3 VO 4 phase with the space group Pnm2 1 over the sintering temperature 700–820 °C for 2–6 h. The results presented that the permittivity, quality factor, and density exhibited a close correlation at different sintering conditions. The homogenous microstructures and outstanding dielectric performances were achieved upon sintering at 730 °C/4h: ε r of 6.65, Q × f value of 15,700 GHz, and τ f of −103 ppm/°C. The intrinsic characteristics of Li 3 VO 4 compounds were also discussed by chemical bond theory. The results indicated that the V(1)–O bonds dominated the contribution to the dielectric properties of the Li 3 VO 4 ceramics. [ABSTRACT FROM AUTHOR]

In this work, garnet structured Ca 3 Yb 2 Ge 3 O 12 ceramics with a space group of Ia- 3 d were synthesized by a solid-state reaction method. Rietveld refinement analysis demonstrated that Yb3+with small ionic radius and large electronegativity entered the B-sites and shortened the bond length of B–O and Ge–O. The bond valence and P-V-L theory analysis results showed that Ca cations with a weakened rattling effect exerted a critical effect on the dielectric constant, and the Ge–O bond was the main factor that influenced dielectric loss. Ca 3 Yb 2 Ge 3 O 12 with a high relative density (98.2%) and excellent microwave dielectric properties (ε r = 10.2, Q × f = 98,400 GHz, τ f = -48 ppm/°C) was obtained at 1360 °C for 4 h. Furthermore, the intrinsic dielectric constant and dielectric loss (ε r =10.12, Q × f = 101,900 GHz) of Ca 3 Yb 2 Ge 3 O 12 were obtained by infrared reflectivity spectroscopy. [ABSTRACT FROM AUTHOR]

Herein, the crystal structure, dielectric properties, and gyromagnetic characteristics of Zn–Sn codoped Y3ZnxSnxFe5−2xO12 (x = 0.0–0.5) prepared using a conventional ceramic process were investigated. According to the first‐principles' calculations and complex crystal bonding theory, Zn2+–Sn4+ codoping can increase the relative dielectric constant (εr) by enhancing the average ionicity. The x‐ray photoelectron spectroscopy (XPS) and Raman analysis results indicate that an appropriate amount of Zn2+–Sn4+ codoping can help improve the microscopic morphology, maintain the appropriate ratio of divalent iron ions, and reduce the microwave magnetic and electrical losses of YIG ferrites. The optimized microwave properties are as follows. Y3Zn0.3Sn0.3Fe4.4O12 after sintering at 1400°C; εr = 15.6; dielectric loss, that is, tanδε = 4.3 × 10−4; saturation magnetization, that is, 4πMS = 2244 G; ferromagnetic resonance linewidth, that is, ΔH = 37 Oe. These properties can help improve the performance of high‐frequency microwave components by enhancing the properties of ferrite. [ABSTRACT FROM AUTHOR]

Gd 2 Mo 3 O 12 ceramics were prepared using the traditional solid-phase reaction method. All samples were found to possess an orthorhombic crystal structure with a space group of Pba2, as revealed by refined XRD results. The ceramic sintered at 1000 °C exhibited a high relative density of 96.95 % and superior microwave dielectric properties, including ε r of 9.42 ± 0.05, × f of 49258 ± 1200 GHz, and τ f of −71.8 ± 0.7 ppm/°C. The results suggest a correlation between an increase in ε r and higher relative density, and a more compact and uniform microstructure can lead to higher × f value. Chemical bonding theories and Raman spectroscopy analysis reveal that Mo-O bonds, rather than Gd-O bonds, dominate the microwave dielectric properties. Furthermore, the ε r of Gd 2 Mo 3 O 12 ceramic was closely related to bond ionicity, while × f and τ f were mainly determined by lattice energy and bond energy, respectively. [ABSTRACT FROM AUTHOR]

Li(1+x)2MgTi3O8 (0.0 ≤ x ≤ 0.10) ceramics with Li non-stoichiometric ratios were prepared by the solid-state reaction method to inhibit the volatilization of Li. The effects of the Li non-stoichiometric ratios on the sintering behavior, crystal structure, microscopic morphology, Raman vibrations, electron density, and dielectric properties of Li(1+x)2MgTi3O8 ceramics were systematically investigated. The Li(1+0.06)2MgTi3O8 ceramics demonstrate the best dielectric properties with εr = 26.33, Q × f = 69 435 GHz (@6.87 GHz, 54% improvement), τf = 2.95 × 10−6 °C−1. For the non-intrinsic factors, the high relative density (97.15%) and larger grain size (16.78 μm) allow the dielectric properties to be improved. As for the intrinsic factors, a reasonable excess of Li improves the bond ionicity of the Mg—O bond, the lattice energy of the Ti—O bond, and the electron cloud density, thus optimizing the dielectric properties. Raman spectroscopy leads to the same result from the point of view of lattice vibrations. At the same time, the distortion of the polyhedra is also improved, so that τf also approaches 0. The improved Li(1+0.06)2MgTi3O8 has potential applications in microwave communication technology.

Novel walstromite-type MCa 2 Si 3 O 9 (M = Ba, Sr) ceramics, with triclinic space group P-1 , were prepared through a solid-state reaction method. The P–V-L theory proves that the lattice energy and bond energy of the Si–O bond play a leading role in the quality factor and the dielectric constant is mainly determined by the ionic polarization. Excellent microwave dielectric properties of BaCa 2 Si 3 O 9 and SrCa 2 Si 3 O 9 ceramics could be obtained: ε r = 8.99 ± 0.23, Q × f = 44,542 ± 500 GHz, and τ f = −25.9 ± 3.0 ppm/°C and ε r = 7.39 ± 0.23, Q × f = 48,772 ± 500 GHz, and τ f = −27.5 ± 3.0 ppm/°C, when sintered at 1240/1280 °C for 4 h. Then SrCa 2 Si 3 O 9 ceramic is applied to a new microstrip bandpass filter, because of its high microwave dielectric properties and low thermal expansion coefficient. With reduced dimension, the filtering performance of the circuit is also highly improved, including reduced capacitor parasitic effect and the optimized stopband insertion loss. Accordingly, the SrCa 2 Si 3 O 9 ceramic is a promising candidate for sub-6 GHz a filter of microstrip bandpass applications. [ABSTRACT FROM AUTHOR]

Novel ultra-low-loss Li 3 Mg 3 NbO 7 ceramics were synthesized using solid-state reaction method. The microstructure, bond characteristics, and microwave dielectric properties (MDPs) of the Li 3 Mg 3 NbO 7 ceramics were explored. Furthermore, the Li 3 Mg 3 NbO 7 ceramics crystallized in the orthorhombic rock-salt structure and the optimized density (97.7%) was obtained at 1200 °C. Utilizing complex chemical bond theory (P–V-L theory) and Raman spectra, the connection between structure and properties was constructed. ε r value was mainly affected by the ρ rel and average ionic polarization. The U Nb – O and packing fraction were the key internal factors influencing the Q × f value. The τ f was intimately relevant to Nb–O bond and τ ε. Notably, the Li 3 Mg 3 NbO 7 ceramics sintered at 1200 °C exhibited excellent MDPs (ε r = 14.7, Q × f = 121,047 GHz, τ f = −24.8 ppm/°C), offering enormous prospects for 5G/6G communication applications. [ABSTRACT FROM AUTHOR]

In this study, crystal structure and microwave dielectric properties of phosphate CaMgP 2 O 7 were comprehensively investigated. As a novel microwave dielectric ceramic, CaMgP 2 O 7 consists of highly dense structure with optimal microwave dielectric properties (ε r = 7.8 ± 0.124, Q×f = 13,165 ± 836 GHz, and τ f = −85.04 ± 1.205 ppm/℃) at a low sintering temperature (950 ℃). The Rietveld refinement of XRD patterns revealed that CaMgP 2 O 7 belongs to a triclinic system with P-1 symmetry type. Moreover, the substitution of Zn2+ for Mg2+ in CaMgP 2 O 7 can further reduce the sintering temperature, effectively promote the densification process, and improve the Q×f value. The effects of porosity (or density) and chemical bond characteristics on the performance of CaMg 1- x Zn x P 2 O 7 ceramics were carefully analyzed as well. Outstanding performance (ε r = 8.05 ± 0.12, Q×f = 20,670 ± 923 GHz, and τ f = −87.59 ± 3.24 ppm/℃) can be achieved for the CaMg 0.84 Zn 0.16 P 2 O 7 ceramic sintered at 875 ℃ for 3 h. [ABSTRACT FROM AUTHOR]

MnMoO 4 ceramic was prepared using solid-state reaction method. XRD and Rietveld refinement results confirmed the formation of a single phase of MnMoO 4 with monoclinic structure of C 2/ m space group. Excellent microwave dielectric properties, including ε r = 9.32, Q × f = 56,230 GHz, and τ f = −62.32 ppm/°C, were achieved for the resulting MnMoO 4 ceramic at 925 °C, which had a relative density of 97%. The dielectric polarization and packing fraction were closely related to the dielectric constant and quality factor of MnMoO 4 ceramics, respectively. Furthermore, our P–V-L analysis demonstrated that the ionicity, lattice energy, and bond energy of chemical bonds were all dominated by the Mo–O bond, which had a greater influence on microwave dielectric properties than the Mn–O bond. This finding was confirmed using Raman spectroscopy, which revealed that [MoO 4 ] tetrahedron vibrations predominated Raman vibrations, supporting the P–V-L theory. Additionally, the chemical compatibility of the MnMoO 4 ceramic with Ag co-firing was explored to investigate potential technological applications. [ABSTRACT FROM AUTHOR]

Two cubic garnet ceramics, Ca 3 B 2 ZnGa 2 O 12 (B = Nb, Sb), were synthesized via the solid-state approach, where Zn2+ and Ga3+ jointly occupied the tetrahedra (C -site), and Nb5+ (or Sb5+) fully occupied the octahedra (B -site). Ca 3 Nb 2 ZnGa 2 O 12 ceramic sintered at 1390 °C possessed a relatively larger ε r , τ f , and Q × f value of 16.57, −44.0 ppm/°C, and 39,200 GHz compared to ε r = 9.04, Q × f = 25,300 GHz, and τ f = −61.2 ppm/°C for Ca 3 Sb 2 ZnGa 2 O 12 fired at 1270 °C. Bond valence, ionic polarizability, packing fraction, Raman spectroscopy, and the P–V-L chemical bond theory were used to investigate the intrinsic factors affecting microwave dielectric properties. Compared with the measured permittivity ε r , the theoretical permittivity ε r (C-M) of Ca 3 Nb 2 ZnGa 2 O 12 is underestimated, and Ca 3 Sb 2 ZnGa 2 O 12 shows the opposite trend, which is mainly related to the under- and over-bonding in the structure. The packing fraction of Ca 3 Nb 2 ZnGa 2 O 12 is slightly lower than that of Ca 3 Sb 2 ZnGa 2 O 12 , but it does not lead to the low Q × f value of Ca 3 Nb 2 ZnGa 2 O 12. The variation in Q × f was related to relative density, weak short-range order (SRO), and lattice energy. The minus sign and magnitude of τ f for both ceramics were determined by their large positive τ αm values. [ABSTRACT FROM AUTHOR]