Effects of Mn2+ doping on the microwave dielectric properties of Ti1-xCux/3Nb2x/3O2 ceramics

In this study, undoped and Mn2+ doped Ti1-xCux/3Nb2x/3O2 (TCN, x = 0.2, 0.25, 0.3, 0.35) ceramics were prepared using a solid-state reaction method. The phase composition and microstructure of the TCN ceramics were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the density and permittivity of the TCN ceramics increase with the increasing of the Cu and Nb content. However, Q x f value of the undoped TCN ceramics decreases with an increase in the sintering temperature. A small amount of Mn2+ doping has no effect on the permittivity, but improves the Q x f value. X-ray photoelectron spectroscopy (XPS) analysis indicated that the transition of Cu2+ to Cu+ during the sintering process could be inhibited by Mn2+ doping, which suppresses the formation of oxygen vacancies, as a result, the improvement of Q x f value. Excellent microwave dielectric properties with a permittivity of 95 and Q x f value of 20800 GHz (@3.50 GHz) were achieved from the 0.6 at% Mn2+ doped TCN (x = 0.25) ceramics sintered at 1025 degrees C for 5 h.