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J. Korean Ceram. Soc. > Volume 57(3); 2020 > Article
Journal of the Korean Ceramic Society 2020;57(3): 314-320.
doi: https://doi.org/10.1007/s43207-020-00035-y
Microwave dielectric properties of Mg4Nb2−x(Zr1/2W1/2)xO9 ceramics
Jeong Hoon Kim, Eung Soo Kim
Department of Advanced Materials Engineering, Kyonggi University, Suwon, Gyeonggi‑do 16227, Korea
Correspondence  Eung Soo Kim ,Email: eskim@kyonggi.ac.kr
Received: January 15, 2020;  Accepted: February 4, 2020.  Published online: March 31, 2020.
ABSTRACT
The relationship between the microwave dielectric properties and structural characteristics of Mg4Nb2−x(Zr1/2W1/2)xO9 (0.05 ≤ x ≤ 0.15) ceramics was investigated along with the microwave dielectric properties of Mg4Nb2−x(Zr1/3W2/3)xO9 (0.05 ≤ x ≤ 0.15) ceramics for comparison. The quality factors (Qf) of Mg4Nb2−x(Zr1/2W1/2)xO9 (MNZW) and Mg4Nb2−x(Zr1/3W2/3)xO9 (MNAW) were proportional to the average bond valence of the Nb-sites. Mg4Nb1.95(Zr1/2W1/2)xO9 (Vavg.B= 3.014), which has a higher average bond valence (VB) than that of Mg4Nb2O9 (VB = 2.991), showed an excellent Qf; however, Qf decreased with further substitution. With an increase in the substitution content, the dielectric constant (K) of the specimens decreased, because the dielectric polarizability of the Nb5+( 3.97 Å3) was larger than that of the substitution ions such as ( Zr1/2W1/2)5+ (3.225 Å3) and ( Al1/3W2/3)5+ (2.397 Å3). The temperature coefficients of resonant frequency (TCF) of the specimens decrease as the K value decreases.
Key words: Dielectric properties · Niobates · Quality factor · Bond valence · Dielectric polarizability
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