Enhancement of dielectric properties in MnTiNb2O8-Based microwave ceramic materials
A novel MnTiNb 2 O 8 -based microwave dielectric ceramic was synthesized by solid-state route and its microwave dielectric properties were investigated. The effects of excess Mn 2+ on the microstructure and microwave dielectric properties of Mn x TiNb 2 O 8 ( x = 1.00–1.20) were investigated. The X-ray diffraction and scanning electron microscopy results showed that MnTiNb 2 O 8 was the dominant crystalline phase in all samples, but TiO 2 , as a second phase, was consistently present. The complex impedance spectroscopy and X-ray photoelectron spectroscopy analysis suggested that the addition of a small amount of Mn could inhibit the formation of oxygen vacancies and hinder the reduction of Ti 4+ . The study found that by adding a small amount of Mn, the quality factor ( Q × f ) of ceramics can be significantly improved without affecting the dielectric constant ( ε r ), thereby greatly optimizing the dielectric properties of ceramics. Subsequently, the temperature coefficient of resonant frequency ( τ f ) of the ceramic was successfully adjusted to near zero by adding a small amount of Zr 4+ instead of Ti 4+ . Among all Mn x Ti 1- y Zr y Nb 2 O 8 ( x = 1.00–1.20, 0 ≤ y ≤ 0.28) ceramics, samples with x = 1.05 and y = 0.1 sintered at 1200 °C showed the best microwave dielectric properties: ε r = 32.9, Q × f = 11,427 GHz, and τ f = 0 ppm/°C.
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