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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]

The structural characteristics and microwave dielectric properties of SrBi2TeO7 ceramics intended for low-temperature co-fired ceramic (LTCC) applications were investigated. Comprehensive analyses were conducted using x-ray diffraction, structural refinement, transmission electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. The findings demonstrated that SrBi2TeO7 ceramics possess a pure cubic structure. Scanning electron microscopy characterizes the grain microstructure, revealing a relative density of 95.5% for SrBi2TeO7 ceramic. Optimal microwave dielectric properties were achieved for SrBi2TeO7 ceramics calcined at 765°C, displaying a relative permittivity (εr) of 24.96, a Q × f value of 25,898 GHz (f = 6.6 GHz), and a temperature coefficient of resonant frequency (τf) of –80.7 ppm/°C. The combination of low sintering temperature and minimal dielectric loss renders these ceramics advantageous for utilization in LTCC materials. [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]

This study presents a comprehensive investigation into the dielectric properties of LiY 9 Si 6 O 26 ceramics, which were prepared for the first time using the solid-state method. XRD patterns and Rietveld refinement analysis conclusively demonstrate that LiY 9 Si 6 O 26 adopts a hexagonal crystal structure with space group P63/m (176). Furthermore, Raman spectroscopy reveals a significant correlation between the quality factor and the FWHM of the A 1g (O) mode at 879 cm−1. Transmission electron microscopy (TEM) was employed to verify the ordered layered structure inherent in the hexagonal LiY 9 Si 6 O 26 ceramics. The microstructure of the ceramic grains was analysed using scanning electron microscopy (SEM), which revealed a remarkably high relative density of 96.4% for the LiY 9 Si 6 O 26 ceramic. The Si–O bond valences (V Si – O) were found to be closely associated with the τ f in LiY 9 Si 6 O 26 ceramics. Remarkably, the microwave dielectric properties of LiY 9 Si 6 O 26 ceramics sintered at 1425 °C were ascertained to be ε r = 10.54, Q × f = 25,579 GHz (f = 10.3 GHz), and τ f = 2.64 ppm/°C. These outstanding properties position LiY 9 Si 6 O 26 ceramics as promising candidates for high-performance dielectric materials. [ABSTRACT FROM AUTHOR]

• ① A novel Nd 2 CaSnO 6 microwave dielectric ceramic was first discovered: ε r = 20.65, Q × f = 27,523 GHz, and τ f = –36.0 ppm/°C. • ② We analyzed the relationship between Raman spectroscopy and microwave dielectric properties. • ③ TEM analysis confirmed the double perovskite structure of Nd 2 CaSnO 6 ceramics. • ④ SEM images revealed the microstructure of the ceramic grains, with the maximum relative density reaching 97.5 %. This study elucidates the synthesis of a new class of Nd 2 CaSnO 6 microwave dielectric ceramics employing the conventional solid-phase method. X-ray diffraction (XRD) patterns and Rietveld refinement analysis revealed that the Nd 2 CaSnO 6 material crystallized into a single phase with an P21/n (14) space group. The double perovskite structure Nd 2 CaSnO 6 ceramics was confirmed through transmission electron microscopy (TEM), the structure exhibits a layered arrangement that is orderly. The internal microstructure was characterized using SEM, which showed that the sample's relative density reached 97.5 %. We discuss the correlation between FWHM and Q × f value of the Raman matrix at the Raman shift of 650.1 cm–1. Additionally, the main factors affecting the dielectric constant were analyzed, including density, secondary phase and porosity changes, etc. The ceramics exhibited remarkable microwave dielectric properties (ε r = 20.65, Q × f = 27523 GHz, and τ f = –36.0 ppm/ °C) when sintered at 1390 °C, indicating their potential as a microwave dielectric material. [Display omitted] [ABSTRACT FROM AUTHOR]

Ceramics of Y 2 GaSbO 7 (YGSO) were prepared by the solid-state reaction method. The ceramics were confirmed by XRD and TEM to exhibit the Fd-3 m (227) space group and a cubic pyrochlore structure within the temperature range of 1420–1500 °C. XPS verified that the valence states of Y, Ga, and Sb in the ceramics were + 3, + 3, and + 5, respectively. Additionally, the relationship between the FWHM of the notable peak at 775 cm−1 and the Q × f value was elucidated through Raman spectroscopic analysis. The analysis of the P-V-L theory revealed that the Sb-O bond is crucial in determining ε r , while the values of τ f and Q × f are affected by the Y-O bond. At 1460 °C, YGSO ceramics obtained the maximum relative density (97.5%) and the best microwave dielectric properties (ε r = 14.78, Q × f = 50,153 GHz, and τ f = –22.3 ppm/°C). • For the first time, a Y 2 GaSbO 7 microwave dielectric ceramic with a pyrochlore structure was discovered. • The Raman spectra of the ceramics were analyzed, and the valence state was studied using XPS. • TEM analysis confirmed the cubic structure of Y 2 GaSbO 7 ceramics. • SEM images revealed the microstructure of the ceramic grains, with the maximum relative density reaching 97.5%. • The relationship between α , f i , E b , U b , and the dielectric properties of Y 2 GaSbO 7 ceramics was examined using P-V-L theory. [ABSTRACT FROM AUTHOR]