Degree of inversion of A/B lattice sites and microwave/millimeter wave/terahertz dielectric properties of MgAl2-x(Zn0.5Mn0.5)xO4 ceramics

In this work, spinel-structured MgAl 2- x (Zn 0.5 Mn 0.5 ) x O 4 (0 ≤  x  ≤ 0.08) single-phase ceramics were prepared through a solid-state reaction route. The substitution of (Zn 0.5 Mn 0.5 ) 3+ for Al 3+ at the octahedral site affected the degree of inversion of A/B lattice sites, bond length/strength/valence, and covalency of metal-oxygen bond in the tetrahedron and hence microwave dielectric properties of MgAl 2 O 4 . The variation in ε r and tanδ of ceramics is investigated in the millimeter wave-terahertz frequency band by combining infrared reflection spectrum and terahertz time-domain spectroscopy. A high Q × f value of 111,010 GHz @ 12.01 GHz, low ε r = 8.3, and slightly lower τ f = −60 ppm/°C is obtained for MgAl 1.98 Zn 0.01 Mn 0.01 O 4 ceramics, which is tuned by adding a small amount of SrTiO 3 . The composite ceramics exhibited a near-zero τ f (2.8 ppm/°C), high Q × f (55,400 GHz @ 11.15 GHz), and low ε r (= 8.5), showing a great potential application prospect for 5G/6G wireless communication.