Complex impedance spectroscopy of perovskite microwave dielectric ceramics with high dielectric constant. Issue 4 (25th September 2018)

• Record Type: Journal Article
• Authors: Wang, Zixing; Yuan, Changlai; Zhu, Baohua; Feng, Qin; Liu, Fei; Xu, Jiwen; Zhou, Changrong; Chen, Guohua
• Is Part Of: Journal of the American Ceramic Society. Volume 102:Issue 4(2019)
• Page Start: 1852
• Page End: 1865
• Publication Date: 2018-09-25
• Subjects: impedance spectroscopy -- microwave ceramics -- perovskite; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.16054
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: The AC impedance of SrTiO3, Ca0.9 Sr0.1 TiO3, Ca0.7 Sm0.2 TiO3, and Ca0.7 Sm0.3 Ti0.7 Al0.3 O3 microwave dielectric ceramics with perovskite structures has been analyzed. The impedance spectroscopy results reveal the electrical properties of this series of samples vary significantly with the ceramic microstructure and electrical homogeneity. The ε r values of grains for SrTiO3 and Ca0.9 Sr0.1 TiO3 ceramics are 193.8 and 138.1, respectively, confirming that dielectric response of the high‐ ε r microwave ceramics is contributed to the grains, at microwave frequencies. Impedance spectroscopy of Ca0.7 Sm0.2 TiO3 ceramic illustrates that electrical heterogeneous microstructures include interior grains and grain shells. The secondary phase existing in Ca0.7 Sm0.2 TiO3 ceramic causes deviation in bulk permittivity, resulting in a higher ε r ~ 148 of grains than ε r ~ 112 of bulk permittivity, measured at microwave frequencies. Grain and grain‐boundary impedance of Ca0.7 Sm0.3 Ti0.7 Al0.3 O3 ceramic cannot be separated completely. The permittivities of grains and grain boundaries in Ca0.7 Sm0.3 Ti0.7 Al0.3 O3 ceramic are ε g ~ 17.8 and ε gb ~ 20.8, and the combination of them is close to ε r ~ 40 at microwave frequencies. The Log I −Log U curves of the ceramic system indicate that the conducting mechanism of grains and grain boundaries follows ohmic behavior.