Effect of Ni substitution on the microwave dielectric properties of cordierite

Cordierite (Mg 2Al 4Si 5O 18) is one of the silicates with low dielectric constant ( ɛ r), which are expected for good candidate of millimeter wave dielectrics. Microwave dielectric properties of Ni substituted cordierite solid solutions; (Mg 1− x Ni x ) 2Al 4Si 5O 18 have been investigated. (Mg 1− x Ni x ) 2Al 4Si 5O 18 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 ( τ f) was observed in the range from x = 0.05 to 0.2, On the other hand, τ f 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.