Giant dielectric constants in K0.8M0.4Ti1.6O4 (M = Ni, Zn) lepidocrocite-type layered titanate ceramics

We reported herein the temperature-dependent dielectric properties of K0.8M0.4Ti1.6O4 (M = Ni, Zn) lepidocrocite titanate ceramics at the frequency f of 10³, 10⁴ and 10⁵ Hz. This titanate is an example of layered alkali titanium oxides possessing two-dimensional (2D) sheets of edge-shared TiO6 octahedra, in contrast to other widely studied materials with mostly corner-shared TiO6 motifs. The giant dielectric constants ε′ ∼10⁴ and the dielectric losses tan δ ∼ 0.5–2 were obtained upon heating from RT to 250 °C. These values in our water-free ceramics are comparable to those previously reported in lepidocrocite titanate and related structures containing up to 15%wt water. The results were explained considering (i) Maxwell-Wagner polarization of interlayer species, and (ii) the possible formation of internal barrier layer capacitors (IBLCs) via the oxidized surfaces.