Enhancement of dielectric properties in MnTiNb2O8-Based microwave ceramic materials

A novel MnTiNb2O8-based microwave dielectric ceramic was synthesized by solid-state route and its microwave dielectric properties were investigated. The effects of excess Mn2+ on the microstructure and microwave dielectric properties of MnxTiNb2O8 (x = 1.00-1.20) were investigated. The X-ray diffraction and scanning electron microscopy results showed that MnTiNb2O8 was the dominant crystalline phase in all samples, but TiO2, 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 Ti4+. The study found that by adding a small amount of Mn, the quality factor (Q x f) of ceramics can be significantly improved without affecting the dielectric constant (epsilon(r)), thereby greatly optimizing the dielectric properties of ceramics. Subsequently, the temperature coefficient of resonant frequency (tau(f)) of the ceramic was successfully adjusted to near zero by adding a small amount of Zr4+ instead of Ti4+. Among all MnxTi1-yZryNb2O8 (x = 1.00-1.20, 0 <= y <= 0.28) ceramics, samples with x = 1.05 and y = 0.1 sintered at 1200 degrees C showed the best microwave dielectric properties: epsilon(r) = 32.9, Q x f = 11,427 GHz, and tau(f) = 0 ppm/degrees C