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Published in:
01-07-2013
Preparation and characterization of K-substituted NaCa4Nb5O17 microwave dielectric ceramics
Published in: Journal of Materials Science: Materials in Electronics | Issue 7/2013
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Abstract
The effect of K substitution for Na on the phase, microstructure and microwave dielectric properties of the Na1−x
K
x
Ca4Nb5O17 (x = 0–1) composition series was investigated. The compositions with x = 0, 0.5 and 1 formed single-phase Na1−x
K
x
Ca4Nb5O17 ceramics within the detection limit of the in-house XRD facility when sintered at 1,200–1,300 °C. At x = 0.25 and 0.75, the major Na1−x
K
x
Ca4Nb5O17 phase formed but along with a secondary CaNb2O6 phase. Relative permittivity (ε
r
) and temperature coefficient of resonant frequency (τf) increased from 45 to 51 and −120 to +473 ppm/ °C respectively while the quality factor (Q × f
o
) decreased from 13,838 to 2,374 GHz with an increase in x from 0 to 1. Optimum microwave dielectric properties (i.e. ε
r
= 47, Q × f
o
= 5,047 GHz and τf = − 23 ppm/ °C) were achieved for the x = 0.5 (i.e. Na0.5K0.5Ca4Nb5O17) composition. Further investigations are required to improve the density and hence microwave dielectric properties of Na1−x
K
x
Ca4Nb5O17 ceramics.