Giant dielectric constants in K_0.8M_0.4Ti_1.6O₄ (M = Ni, Zn) lepidocrocite-type layered titanate ceramics

Abstract

We reported herein the temperature-dependent dielectric properties of K_0.8M_0.4Ti_1.6O₄ (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.

Keywords:

• Lepidocrocite
• alkali titanate
• layered structure
• dielectric properties

Additional information

Funding

This work was partly supported by the National Nanotechnology Center (NANOTEC), NSTDA, Ministry of Science and Technology, Thailand, through its program of Center of Excellence Network.