Title
Crystal structure, phonon modes, and bond characteristics of AgPb2B2V3O12 (B = Mg, Zn) microwave ceramics
Author
Rakhi Madhuri; Subodh Ganesanpotti
Year
2019
Journal
Journal of The American Society
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 urn:x-wiley:00027820:media:jace16991:jace16991-math-0001. The number of observed vibrational modes and those predicted by group theoretical calculations also confirm the urn:x-wiley:00027820:media:jace16991:jace16991-math-0002 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 (urn:x-wiley:00027820:media:jace16991:jace16991-math-0003) of 26 900 ± 500 GHz (urn:x-wiley:00027820:media:jace16991:jace16991-math-0004), 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 (urn:x-wiley:00027820:media:jace16991:jace16991-math-0005) 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 urn:x-wiley:00027820:media:jace16991:jace16991-math-0006 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.
Instrument
FTIR-6800
Keywords
Fourier transform infrared spectroscopy, microwave ceramics,