Abstract
Non-stoichiometric Nd[Mg0.5Sn0.5(1+x)]O3 (− 0.04 ≤ x ≤ + 0.04)—type samples were prepared using a traditional two-step solid-state sintering process. Their crystal structures, phase compositions, dielectric properties and lattice vibrational characteristics were identified in detail. The double perovskite Nd(Mg0.5Sn0.5)O3 with a monoclinic structure was distinguished as the main crystalline phase, and pure phase was obtained when x < 0. The sample [Nd(Mg0.5Sn0.49)O3] at x = − 0.02 shows the excellent dielectric properties: er = 18.74, Q × f = 47,979 GHz. The lattice vibrational characteristics were clarified with Raman and infrared active mode spectroscopy. The intrinsic properties were fitted by four-parameter semi-quantum model, which show that the low-frequency infrared modes yield a more significant contribution to permittivity and dielectric loss. Raman shifts of modes F2g(A) and F2g(B) correlate with dielectric constants negatively, which implies that the bond length has a positive correlation with permittivity. Full widths at half maximum of vibrational modes A1g(O) correlate with dielectric loss values positively and correlate with the degree of order (S) negatively.
Highlights
Microwave dielectric ceramics (MWDCs) have been widely used as application-driven materials for the manufacture of various microwave components, which are fundamental to modern microwave communication, such as mobile communication, satellite communication, global positioning system, and wireless local area network[1,2,3]
Nd(Mg0.5Sn0.5)O3 can be clearly distinguished as the main crystalline phase, which belongs to a monoclinic crystal structure (P21/n space group) with a double perovskite structure
The reason is that Mg2+ can volatilize at higher sintering temperature during the reaction process, but excess Sn4+ can promote the generation of the secondary phase. (100) and 1/2(210) peaks move to lower angles from -0.04 to -0.02 and to higher angles from -0.02 to +0.04, as shown in the inset figure, which indicates that the lattice volume of the samples increases first from -0.04 to -0.02 and decreases from -0.02 to +0.04
Summary
Microwave dielectric ceramics (MWDCs) have been widely used as application-driven materials for the manufacture of various microwave components, which are fundamental to modern microwave communication, such as mobile communication, satellite communication, global positioning system, and wireless local area network[1,2,3]. Previous researches on rare-earth based A(B'0.5B''0.5)O3-type MWDCs are mostly concentrated on the basic structures of pure phase ceramics, lowering sintering temperature by sintering aid, and enhancing property by doping, but few research focused on the influence of nonstoichiometry on the crystal structures and dielectric properties, especially non-stoichiometric Nd(Mg0.5Sn0.5)O3 system. Research on the non-stoichiometric Nd(Mg0.5Sn0.5)O3 ceramics contributes to understand the composition control, defect chemistry, crystal structures, dielectric properties, and performance regulation of rare-earth based A(B'0.5B''0.5)O3-type MWDCs. In addition, Raman scattering spectroscopy and far-infrared reflection spectroscopy were often used to investigate the lattice vibrational characteristics of solid-state materials[10,11,12,13], which helps to analyze macroscopic properties from a microscopic perspective and provides more innovative perspectives in inherent attribute and structure-property regulation. The structure-property correlations were established using Raman active phonon modes as a media so as to contribute to the design of new-type MWDCs from the perspective of material science as a furthers study basen on the previous results[17,18]
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