A novel Na <sub>1− <i>x</i> </sub>K <sub> <i>x</i> </sub>TaO <sub>3</sub> perovskite microwave dielectric ceramic with high permittivity and high positive temperature coefficient
Liu Tang, Hongcheng Yang, Enzhu Li, Chaowei Zhong
Abstract
A novel Na<sub>1-<em>x</em></sub>K<em><sub>x</sub></em>TaO<sub>3</sub> (<em>x </em>= 0, 0.025, 0.05, 0.075, 0.1, and 0.15) ceramic with high permittivity and high positive temperature coefficient<strong> </strong>was synthesized via the conventional solid-state method. All samples were determined to be pure phase orthorhombic NaTaO<sub>3</sub> structure of space group Pmcn, and larger grain and lower porosity were observed after adding an appropriate amount of K<sup>+</sup> ions. The <em>Q × f</em> value is majored by the packing fraction and grain size, while the value of <em>τ<sub>f</sub></em> is influenced by Ta-O bond valence. The Na<sub>0.95</sub>K<sub>0.05</sub>TaO<sub>3</sub> ceramic possesses excellent dielectric properties of <em>ε<sub>r</sub></em> = 164.29， <em>Q × f</em> = 9091 GHz (<em>f </em>= 3.15 GHz）， tan<em>δ</em> = 3.46 × 10<sup>-4</sup>， <em>τ<sub>f</sub></em> = +809.52 ppm/°C, sintered at 1550 °C. Compared with NaTaO<sub>3</sub> ceramics, the Na<sub>1-<em>x</em></sub>K<em><sub>x</sub></em>TaO<sub>3</sub> ceramics prepared in this study demonstrate higher dielectric constants and higher positive temperature coefficients, which are promising for device miniaturization and <em>τ<sub>f </sub></em>compensators.