Crystal structure, phonon modes, and bond characteristics of AgPb₂B₂V₃O₁₂ (B = Mg, Zn) microwave ceramics

Abstract

AgPb2B2V3O12 (B = Mg, Zn) ceramics with low sintering temperature were synthesized via the conventional solid‐state reaction route. Rietveld refinements of the X‐ray diffraction patterns confirm cubic symmetry with space group Ia3¯d. The number of observed vibrational modes and those predicted by group theoretical calculations also confirm the Ia3¯d space group. At the optimum sintering temperature of 750°C/4 hours, AgPb2Mg2V3O12 has a relative permittivity of 23.3 ± 0.2, unloaded quality factor (Qnormalu×f) of 26 900 ± 500 GHz (f=7.57GHz), and temperature coefficient of resonant frequency of 19.3 ± 1 ppm/°C, while AgPb2Zn2V3O12 has the corresponding values of 26.4 ± 0.2, 28 400 ± 500 GHz (f=7.21GHz) and –18.4 ± 1 ppm/°C at 590°C/4 hours. Microwave dielectric properties of a few reported garnets and Pb2AgB2V3O12 (B = Mg, Zn) ceramics were correlated with their intrinsic characteristics such as the Raman shifts as well as width of A1g Raman bands. Higher quality factor was obtained for lower full width at half‐maxima (FWHMs) values of A1g modes. The increase in B‐site bond valence contributes to high Qnormalu×f and low |τf| with the substitution of Zn2+ by Mg2+. Furthermore, the high ionic polarizability and unit cell volume with Zn2+substitution contribute to increased relative permittivity.

Sintering behavior, crystal structure, and microwave dielectric properties of a novel NaY9Si6O26 ceramic

“…39 There is a linear relationship between the high frequency band of 800-1000 cm −1 and lattice parameters. 40,41 Additionally, a robust Raman crest value at approximately 419 cm −1 results from a symmetrically bent v2 mode, whereas fainter Raman bands associated with the asymmetric bent v3 mode and v4 mode materialize at 544 and 958 cm −1 , respectively. 42 Figure 5B intricately depicts the dynamic interplay between the Q × f value of NaY 9 Si 6 O 26 ceramics sintered at diverse temperatures and the full width at half maximum (FWHM) of the A 1g (O) stretching vibration mode at 878 cm −1 .…”

“…Notably, a conspicuous crest emerges around 878 cm −1 , denoting the symmetric stretching mode A 1g (O) of the SiO 4 tetrahedron 39 . There is a linear relationship between the high frequency band of 800–1000 cm −1 and lattice parameters 40,41 . Additionally, a robust Raman crest value at approximately 419 cm −1 results from a symmetrically bent v2 mode, whereas fainter Raman bands associated with the asymmetric bent v3 mode and v4 mode materialize at 544 and 958 cm −1 , respectively 42 …”

Insights Into the Microstructure and Dielectric Properties of Cold Sintered NaCa2Mg2V3O12 Based Composites

“…The C ions form CO 4 tetrahedra, while the B-site ions form octahedral coordination with the oxygen atoms. The corner-shared octahedra and tetrahedra form dodecahedra, where the A-site ions are placed (Rakhi and Subodh, 2020). Among this, Fang et al studied dielectric properties of NaCa 2 Mg 2 V 3 O 12 ceramic, which possesses relative permittivity of 10, quality factor around 50,600 GHz and temperature coefficient of resonant frequency of −47 ppm/ • C (Fang et al, 2013).…”

Phase Composition, Crystal Structure and Microwave Dielectric Properties of Nb-Doped Yttrium Aluminum Garnet Ceramics

“…Reportedly [28], According to calculations, when the Nb 5+ ions enter the aluminium oxygen octahedron [AlO6] replacing Al 3+ , both the bond valence and bond strength decrease. Generally in oxygen octahedra, when the bond valence between anions and cations decreases, the bond strength also decreases, implying that the structure tends to be unstable [29], which also explains the deterioration of the τf values.…”