The dimensional effect of MgTiO3 ceramic filler on the microwave dielectric properties of PTFE/MgTiO3 composite with ultra-low dielectric loss

PTFE matrix loaded with different volume fractions of MgTiO3 ceramic powder with particle sizes of around 5m and 15m (abbreviated as MT-5 and MT-15, respectively) was prepared. The microstructure, microwave dielectric properties and thermal properties of the composites were studied by scanning electron microscope, vector network analyzer and thermal dilatometer. The results show that PTFE/MT-15 composite exhibits higher relative density and better dielectric properties than the PTFE/MT-5 composite, since the former with coarse particles possesses lower surface energy to weaken the particle agglomeration effect. Even at 40% filler volume fraction, the ultra-low dielectric loss of PTFE/MT-15 composite can be maintained in the order of 10(-4)at 10GHz. Different models are used to predict the dielectric constant of the composites. Among which, the effective medium theory shows the least deviation from the experimental results. PTFE matrix filled with 40V% MT-15 ceramic powder shows excellent microwave dielectric properties: epsilon(r)=5.5, tan=2.7x10(-4) (at 10GHz), which may be a promising material in electronic packaging field.