AC Conductivity and Dielectric Properties of Lepidocrocite-type Alkali Titanate Tunable by Interlayer Cation and Intralayer Metal.

The lepidocrocite-type layered alkali titanate TiO has diverse chemical compositions with variation in charge per formula unit , the interlayer cation , and the intralayer metal . Despite this multivariable nature, the composition dependence of physical properties is not well explored. We report herein the AC conductivity and the complementary dielectric properties of CsTiO, KTiO ( = Zn, Ni), and the mixed-interlayer ion CsKZnTiO. For CsZnTiO, the total AC conductivity is ∼7 × 10 to 2 × 10 S·cm at 200-350 °C, associating with an activation energy ∼ 865 meV. Meanwhile, the conductivity of KZnTiO is higher by 1 order of magnitude at much lower temperature (25-150 °C) and a smaller ∼ 250 meV. This difference originates from the compositional robustness of the cesium-containing samples, contrasting with the sintering-induced changes in the potassium analogues. For the latter, the loss of the interlayer K ion results in (i) generation of carriers due to charge compensation, (ii) reduction of sheet charge density and weakening of electrostatic attraction, and (iii) widening of the interlayer distance, all contributing to a lower in KTiO. The angular frequency dependence of conductivity, dielectric permittivity (up to a colossal value of 10), and dielectric loss follows the universal power law. Our work demonstrates the potential of simple compositional variation for electrical properties tuning, prompting a more in-depth investigation covering a wider range of possible candidates of , , and in lepidocrocite titanate.