Effect of CuO on Crystallization Behavior and Microwave Dielectric Properties of Cordierite Glass-Ceramics
The xCuO-(22.2-x)MgO-22.2Al2O3-55.6SiO2(x=0,0.25,0.50,0.75 and 1.00,molar fraction)(MAS)glass-ceramics were synthesized using sintering-crystallization method.The effect of CuO content on the crystallization behavior,crystal type,micromorphology and microwave dielectric properties of MAS glass-ceramics was studied.The results show that as the CuO content increases from 0％to 1.00％,substituting for MgO,the glass transition temperature decreases.Additionally,the precipitation peak temperatures also show a decreasing trend,while the Avrami index n gradually increases.The primary crystalline phase in glass-ceramics is α-cordierite.The inclusion of CuO facilitates the transformation of μ-cordierite to α-cordierite at lower temperatures and reduces the thermal expansion coefficient.With the increase of CuO content,the dielectric constant of glass-ceramics increases first and then decreases,while the dielectric loss decreases first and then increases.At a heat treatment 650 ℃/2 h+1 050 ℃/2 h,the glass-ceramics doped with 0.25％and 0.50％CuO exhibits optimal integrated dielectric properties,which dielectric constant is 5.04 and 5.07,dielectric loss is 7.49 ×10-4 and 7.12×10-4,and quality factor is 20 013.35 and 20 786.41 GHz within the frequency range of 14.6～15.2 GHz.
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