A novel Na_1−xK_xTaO₃ perovskite microwave dielectric ceramic with high permittivity and high positive temperature coefficient

A novel Na_1−xK_xTaO₃ (x = 0, 0.025, 0.05, 0.075, 0.1, and 0.15) ceramic with high permittivity and high positive temperature coefficient was synthesized via the conventional solid-state method. All samples were determined to be pure phase orthorhombic NaTaO₃ structure of space group Pmcn, and larger grain and lower porosity were observed after adding an appropriate amount of K⁺ ions. The Q × f value is majored by the packing fraction and grain size, while the value of τ_f is influenced by Ta–O bond valence. The Na_0.95K_0.05TaO₃ ceramic possesses excellent dielectric properties of ε_r = 164.29, Q × f = 9091 GHz (f = 3.15 GHz), tanδ = 3.46×10^–4, τ_f = +809.52 ppm/℃, sintered at 1550 ℃. Compared with NaTaO₃ ceramics, the Na_1−xK_xTaO₃ ceramics prepared in this study demonstrate higher dielectric constants and higher positive temperature coefficients, which are promising for device miniaturization and τ_f compensators.