Electrical properties of Al–ZrMgMo3O12 with controllable thermal expansion

Abstract Al–ZrMgMo 3 O 12 composites samples were prepared by the solid state method. The crystal phase and microstructure of the composites were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns show two phases of Al and ZrMgMo 3 O 12 . The SEM images show the microstructures of the ceramics containing particles of ZrMgMo 3 O 12 and blocks of Al–ZrMgMo 3 O 12 . The ratio of particles to blocks changed on adjusting the mass ratio of Al:ZrMgMo 3 O 12 , consequently changing the coefficient of thermal expansion (CTE) and the electrical properties of the composites. When the mass ratio of Al:ZrMgMo 3 O 12 is 2:8 the CTE is 0.77×10 −6  K −1 (room temperature to 673 K), which corresponds to a near-zero thermal expansion dielectric material. For Al–ZrMgMo 3 O 12 composite with mass ratio of 6:4, the CTE (8.72×10 −6  K −1 ) is reduced to one-third of that of Al (23.79×10 −6  K −1 ) and the impedance is decreased to 7.68 Ω. The conductivity change of Al–ZrMgMo 3 O 12 composites can be attributed to the conductive percolation phenomenon, resulting from the presence of large mixed blocks of Al–ZrMgMo 3 O 12 among the particles of ZrMgMo 3 O 12 .