Effect of Ni substitution on the microwave dielectric properties of cordierite

Cordierite (Mg2Al4Si5O18) is one of the silicates with low dielectric constant (ɛr), which are expected for good candidate of millimeter wave dielectrics. Microwave dielectric properties of Ni substituted cordierite solid solutions; (Mg1−xNix)2Al4Si5O18 have been investigated. (Mg1−xNix)2Al4Si5O18 with no secondary phase was obtained in the compositions x range from 0 to 0.1. It was found that a very small amount of Ni substitution was effectively increased of the quality factor (Qf) value and the highest Qf value of 99,110 GHz was obtained in the composition x = 0.1. No remarkable composition dependence of the temperature coefficient of resonance frequency (τf) was observed in the range from x = 0.05 to 0.2, On the other hand, τf abruptly shifted toward negative value with increasing x from 0.3 to 0.5. The correlation between the crystal structure of cordierite and the microwave dielectric properties, particularly Qf is discussed.