Structure and Microwave Dielectric Characteristics of Ca1+xNd1−xAl1−xTixO4 Ceramics |
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Authors: | Hong Xia Yuan Xiang Ming Chen Min Min Mao |
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Affiliation: | Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China |
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Abstract: | CaNdAlO4 microwave dielectric ceramics were modified by Ca/Ti co-substitution, and their dielectric characteristics were evaluated along with their structure and microstructures. Ca1+ x Nd1? x Al1? x Ti x O4 ( x =0, 0.025, 0.05, 0.10, 0.15, 0.20) ceramics with the relative density of over 95% theoretical density were obtained by sintering at 1400°–1450°C in air for 3 h, where the K2NiF4-type solid solution single phase was determined from the compositions of x <0.20, while a small amount of CaTiO3 secondary phase was detected for x =0.20. With Ca/Ti co-substitution in CaNdAlO4 ceramics, the dielectric constant (?r) increased with increasing x , and the temperature coefficient of resonant frequency (τf) was adjusted from negative to positive, while the Q × f 0 value increased significantly at first and reached an extreme value at x =0.025 and the maximum at x =0.15. The best combination of microwave dielectric characteristics were achieved at x =0.15 (?r=19.5, Q × f 0=93 400 GHz, τf=?2 ppm/°C). The improvement of the Q × f 0 value primarily originated from the reduced interlayer polarization with Ca/Ti co-substitution, while the decreased tolerance factor, the subsequent increased interlayer stress, and the appearance of CaTiO3 secondary phase brought negative effects upon the Q × f 0 value. |
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