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This research demonstrates the microwave dielectric properties of Ba 2 Bi 2/3 TeO 6 ceramics, synthesized for the first time via the solid-state method, for LTCC applications. The analysis of X-ray diffraction (XRD) patterns and structural refinement verify the double perovskite structure of Ba 2 Bi 2/3 TeO 6 ceramics. Transmission electron microscopy (TEM) validates the ordered layered structure of the double perovskite Ba 2 Bi 2/3 TeO 6 ceramics. Scanning electron microscopy (SEM) characterizes the grain microstructure, revealing a relative density of 99.1% for the sample. An inverse proportionality is observed between the Raman full-width at half maximum (FWHM) and the Q × f value. X-ray photoelectron spectroscopy (XPS) elucidates the chemical composition and valence states of the Ba 2 Bi 2/3 TeO 6 ceramic elements. The microwave dielectric properties of Ba 2 Bi 2/3 TeO 6 ceramics calcined at 935 °C were discovered to be ε r = 11.94, Q × f = 21,579 GHz (f = 9.8 GHz), and τ f = −22.4 ppm/°C. Ba 2 Bi 2/3 TeO 6 ceramics emerge as an excellent candidate for LTCC applications. [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]