Li4Mg3Ti2O9: A novel low-loss microwave dielectric ceramic for LTCC applications

Low-loss novel Li 4 Mg 3 Ti 2 O 9 dielectric ceramics with rock-salt structure were prepared by a conventional solid-state route. The crystalline structure, chemical bond properties, infrared spectroscopy and microwave dielectric properties of the abovementioned system were initially investigated. It could be concluded from this work that the extrinsic factors such as sintering temperatures and grain sizes significantly affected the dielectric properties of Li 4 Mg 3 Ti 2 O 9 at lower sintering temperatures, while the intrinsic factors like bond ionicity and lattice energy played a dominant role when the ceramics were densified at 1450   °C. In order to explore the origin of intrinsic characteristics, complex dielectric constants ( ε ’ and ε ’’ ) were calculated by the infrared spectra, which indicated that the absorptions of phonon oscillation predominantly effected the polarization of the ceramics. The Li 4 Mg 3 Ti 2 O 9 ceramics sintered at 1450   °C exhibited excellent properties of ε r =15.97, Q· f =135,800   GHz and τ f =−7.06   ppm/°C. In addition, certain amounts of lithium fluoride (LiF) were added to lower the sintering temperatures of matrix. The Li 4 Mg 3 Ti 2 O 9 −3   wt% LiF ceramics sintered at 900   °C possessed suitable dielectric properties of ε r =15.17, Q· f =42,800   GHz and τ f =−11.30   ppm/°C, which made such materials promising for low temperature co-fired ceramic applications (LTCC).