xAl2O3-(1-x)Sr0.85Gd0.15TiO3(x=0.2, 0.3, 0.4, 0.5) ceramics were fabricated by hot-press sintering. Their morphology, phase composition, conductivity, dielectric properties as well as microwave absorption performance were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), multifunction digital four-probe meter and vector network analysis, respectively. The microwave absorption of as-prepared xAl2O3-(1-x)Sr0.85Gd0.15TiO3 ceramics demonstrates excellent microwave absorbability. It is unexpectedly found that with a thickness of only 0.346 mm, xAl2O3-(1-x)Sr0.85Gd0.15TiO3 (x=0.2) ceramic exhibits an absorption bandwidth of 3.7 GHz (8.7-12.4 GHz), being consequential to reflection loss less than -10 dB (over 90% of microwave absorption). It is as well discovered that the minimum reflection loss and absorption peak frequency of xAl2O3-(1-x)Sr0.85Gd0.15TiO3 (x=0.3) with a thickness of 0.436 mm were -45.43 dB and 11.3 GHz, respectively. The prominent microwave absorption performance of the ceramic with such a thin thickness can be attributed to strong interfacial polarization, dielectric frequency dispersion, and good electromagnetic impedance matching. It indicates that the xAl2O3-(1-x)Sr0.85Gd0.15TiO3 ceramics with appropriate Al2O3 mass fraction and thickness showing good potential for effective microwave absorbing materials.

Recently, high-temperature stability is a challenge in a number of microwave absorption materials. Hence, researchers are still searching for a novel material system preferably with a high-temperature resistance to be applied in the field of microwave absorption. Here, in the current study, toward this aim, lanthanum (La) doped strontium titanate (SrTiO 3 ) blended with TiO 2 were fabricated by hot-press sintering in vacuum. The as-prepared samples are denoted as TiO 2 -Sr 1- x La x TiO 3 with x varying from 0.1 to 0.3 in steps of 0.1. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), and microwave vector network analyzer were carried on to study their morphology, phase composition, structure, electromagnetic and microwave absorption properties, respectively. It is revealed that the La atom was efficiently doped at the Sr-site in SrTiO 3 . Benefiting from the tunability of its dielectric and impedance properties, TiO 2 -Sr 1- x La x TiO 3 can be utilized in a highly efficient way to absorb microwave radiations with a decent design. Results illustrated that TiO 2 -Sr 1- x La x TiO 3 ( x =0.2) with a thickness of only 0.42 mm exhibits a high microwave absorption efficiency of -40.89 dB and can achieve a 2.82 GHz bandwidth of reflection loss value below -5 dB. Thus, TiO 2 -Sr 1- x La x TiO 3 composites ceramics can be served as an opening opportunity for the application of high-temperature stability and tunable high-performance effectiveness microwave absorption materials in stealth technology and information security.