Enhancing the thermal stability of the dielectric property by tilting the NbO₆ octahedra in (Na_1-zK_z)NbO₃-SrTiO₃ceramics

초록

(1-x) (Na0.2K0.8)NbO3-xSrTiO(3) [(1-x) (N0.2K0.8)N-xST] ceramics with a homogeneous perovskite structure were well-sintered in the range of 1080-1160 degrees C. The 0.9(N0.2K0.8)N-0.1ST ceramic was found to have a temperature-stable dielectric constant (epsilon(r)) that complies with the X9R multilayer ceramic capacitor (MLCC) requirement. The temperature stability of the epsilon(r) value was also investigated for the 0.9(N1-zKz)N-0.1ST ceramics (0.0 <= z <= 1.0). The results indicated that as z (or K+ ions) increased, the Curie temperature (T-C) decreased, and its peak broadened. The broadening of the T-C peak was attributed to the development of the relaxor property owing to the tilting of the NbO6 octahedra. The 0.9(N1-zKz)N-0.1ST ceramics (0.7 <= z <= 1.0) exhibited a temperature-independent epsilon(r) value, thus fulfilling the X9R MLCC requirement because of the broad T-C peak. The MLCC fabricated from 0.9(N0.2K0.8)N-0.1ST thick films complied with the X9R MLCC requirement with excellent capacitance stability under the supplied electric field. Hence, 0.9(N1-zKz)N-0.1ST ceramics (0.7 <= z <= 1.0) are good candidates for X9R MLCCs.

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