Improvement in dielectric properties of Al2O3-doped Li0.30Cr0.02Ni0.68O ceramics

Li0.30Cr0.02Ni0.68O giant dielectric ceramics doped with Al2O3 were prepared by solid-state reaction via sol–gel process. The sintered samples were characterized using X-ray powder diffraction and scanning electron microscopy, and dielectric properties were also investigated. All doped samples showed the single phase of cubic rock-salt structure NiO. With increasing Al2O3 content, the crystallite size and grain size decreased, possibly due to an occurrence of the secondary phases at grain boundaries which inhibit the grain growth. The sample with 0.2 wt.% Al2O3 showed nearly 7 times lower tanδ (2.37) and higher εr (7.25 × 106) measured at 1 kHz and room temperature when compared to the pure sample.