Sintering behavior, crystal structure and microwave dielectric properties of (1−x)Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃– x(Na_0.5Nd_0.5)TiO₃ ceramics

(1−x)Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃–x(Na_0.5Nd_0.5)TiO₃ (x = 0, 0.2, 0.4, 0.6, 0.8) ceramics were prepared using the solid–state reaction route. The effects of (Na_0.5Nd_0.5)TiO₃ content on the sintering behavior, structural characteristics and microwave dielectric properties of Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃ were investigated in detail. (1−x)Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃–x(Na_0.5Nd_0.5)TiO₃ ceramics exhibited different sintering characteristics in the whole investigated compositional range. X–ray diffraction analysis showed that a complete solid solution with perovskite structure formed in the composition range of x = 0.2–0.8. Moreover, a structural change from the monoclinic to the cubic perovskite structure occurred at x = 0.8. Compared with the pure Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃ ceramics, (1−x)Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃–x (Na_0.5Nd_0.5)TiO₃ ceramics displayed more anomalous microstructural characteristics. Microwave measurements indicated that the dielectric constant (ε_r) increased from 31.15 to 78.4, the quality factor (Q × f) value decreased from 2151300 GHz to 12013 GHz, and the temperature coefficient of resonant frequency (τ_f) moved to positive from −35.7 ppm/°C to +59.1 ppm/°C with the x value increasing from 0 to 0.8. Typically, 0.6Nd[(Zn_0.7Co_0.3)_0.5Ti_0.5]O₃–0.4(Na_0.5Nd_0.5)TiO₃ ceramics sintered at 1410 °C for 4 h possessed excellent microwave dielectric properties of ε_r = 50.21, Q × f = 54714 GHz, τ_f = −3 ppm/°C.