Correlations between crystal structure and microwave dielectric properties of Mn2+-substituted ZnTiNb2O8 ceramics
Zn 1− x Mn x TiNb 2 O 8 (0.05 ≤ x ≤ 0.30) microwave dielectric ceramics were synthesized by the solid-state reaction method. The impacts of partial substitution of Mn 2+ for Zn 2+ on the crystal phase, crystal structure, grain morphology, and microwave dielectric properties were investigated in detail. Minor ixiolite phase of MnTiNb 2 O 8 was detected via the X-ray diffraction at higher x levels. Structural characteristics, such as porosity, packing fraction, and [Zn/Ti/NbO 6 ] octahedron distortion, were discussed to reveal the correlations between the microwave dielectric characteristics and the crystal structure. It was suggested that the permittivity was related to the porosity and the minor phase, while the quality factor was mainly determined by the packing fraction and relative density. The temperature coefficient of the resonant frequency was positively correlated with the distortion of [Zn/Ti/NbO 6 ] octahedron. Among all Zn 1− x Mn x TiNb 2 O 8 ceramics, the sample of x = 0.05 sintered at 1100 °C exhibited good microwave dielectric properties: ε r = 35.91, Q × f = 63,672 GHz (at 6.52 GHz), and τ f = − 68.68 ppm/°C, which provided an effective performance modulating approach for microwave dielectric ceramic design.
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