Effect of cation occupancy on crystal structure and microwave dielectric characteristics of spinel-structured (1-x)Zn2TiO4-xli2MgTi3O8 ceramics

Excellent spinel microwave dielectric ceramics (1- x )Zn 2 TiO 4 - x Li 2 MgTi 3 O 8 (ZTLMT x , x  = 1/3 and 2/3) were prepared at relatively low densification temperatures of 1100 °C and 1080 °C, respectively. A disordered cubic phase with space group Fd -3 m was formed at x  = 1/3, whereas an ordered cubic phase with space group P 4 3 32 was formed at x  = 2/3. The ceramics at x  = 1/3 and 2/3 exhibited promising microwave dielectric properties of ɛ r  = 18.27 and 22.96, Q  ×  f  = 91,877 GHz and 75,186 GHz, and τ f  = −42.3 ppm/°C and −21.05 ppm/°C, respectively. The large deviation between the experimental ԑ r and theoretical ε th of 1/3 and 2/3 ceramics were 18.3 % and 57 %, respectively, due to the underestimation of the ionic polarizability of Ti 4+ . The difference in their ɛ r , Q  ×  f , and τ f were discussed by the structure, FWHM of A 1g , lattice energy and bond energy in detail.