Mechanical strength and microwave dielectric properties of Al₂O₃ doped Li₂MgTi₃O₈ ceramics with high temperature stability

A temperature stability microwave dielectric ceramic with composition of Li2MgTi3O8 (LMT) and Al2O3 with high flexural strength is synthesized by a conventional solid-state reaction method. The effects of Al2O3 (particles and whiskers) doping on the mechanical and dielectric properties of LMT ceramics are studied. A single spinel structure, without any secondary phases, is detected in the Al2O3 particles and Al2O3 whiskers doped LMT ceramics. The maximum flexural strengths of 152.5 MPa and 166.73 MPa are delivered in LMT +0.3 wt% Al2O3 (p) ceramics and LMT + 0.3 wt% Al2O3 (w) ceramics, respectively, which are enhanced by 53.21% and 67.52% over those of unmodified LMT ceramics. Pinning and grain refinement contribute to the enhanced flexural strength of the system. The intrinsic factors of Q x f change are analyzed by calculating the packing fraction and lattice energy. In addition, ceramics exhibit excellent comprehensive microwave properties at 1050 degrees C: (LMT + 0.2 wt% Al2O3 (p):Q x f = 67056 GHz, tau(f) = -8.25 ppm/degrees C, epsilon(r) = 24.34, sigma(f) = 133.3 MPa; LMT + 0.1 wt% Al2O3(w): Q x f = 68670 GHz, tau(f) = -8.94 ppm/degrees C, epsilon(r) = 24.32, sigma(f) = 122.7 MPa) The results indicate that Al2O3 particles and Al2O3 whiskers are decent reinforcing agents for LMT ceramics.