Structure and Microwave Dielectric Properties of Ba5[Nb1-x(Al1/3Mo2/3)x]4O15 Ceramics
With the comprehensive and rapid development of mobile communications,it is urgent to research and develop new microwave dielectric ceramic materials with medium εr and high Q value and low frequency temperature coefficient.In this work,(Al1/3 Mo2/3)5+were introduced into the B-site of the deficiency-type hexagonal perovskite ceramic Ba5Nb4O15 by solid-phase reaction method to investigate the effects of ion substitution on its phase composition,microstructure and microwave dielectric properties.The analysis shows that the moderate amount of(Al 1/3 Mo2/3)5+substitution is favorable for the densification and sintering of Ba5Nb4O15 ceramics,however,when the doping amount is too much,the complete solid solution is not formed and the second phase BaMoO4 appears,which affects the microwave dielectric properties of the ceramic matrix to a certain extent.With increasing substitution,the dielectric constant and Qxf value of Ba5[Nb1-x(Al1/3Mo2/3)x]4O15 ceramics show a decreasing trend,but the composite substitution makes the τf value move in the negative direction.When x=0.1,the ceramic samples sintered at 1 385 ℃ have the optimal microwave dielectric properties:εr=37,Qxf=10 300 GHz,τf=6.5x10-6/℃.The experimental results show that the modified Ba5Nb4O15 ceramic dielectrics can be used as a candidate material for high-reliability mobile communication devices.
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