Microwave dielectric properties of temperature stable CoTiNb2O8-CoNb2O6 composite ceramics

(1 - x)CoTiNb2O8-xCoNb(2)O(6) microwave dielectric ceramics were synthesized via conventional solid-state reaction route. Compositionally induced phase formation was investigated by X-ray diffraction. For the CoNb2O6-added compounds, rutile-structured CoTiNb2O8 and columbite phase were coexisted without any secondary phases. The microwave dielectric properties were strongly related to the density, sintering condition, and chemical composition of samples. As expected, CoNb2O6 addition from 0.5 to 0.83 led to a decrease in the epsilon(r) from 43.0 to 27.2. In contrast, Qxf increased considerably, attributing to the CoNb2O6 phase and enhanced densification. When sintered at 1200 degrees C, the 0.2CoTiNb(2)O(8)-0.8CoNb(2)O(6) ceramic possessed excellent microwave dielectric properties with epsilon(r)similar to 28.9, Qx f similar to 36,948 GHz (at 8.1 GHz), and tau(f)similar to 0.5 ppm/degrees C. (C) 2016 Elsevier B.V. All rights reserved.