Computational and experimental investigations of the giant dielectric property of NaYCuTiO ceramics.

A modified sol-gel method was used to successfully produce NaYCuTiO ceramics with high dielectric permittivity. The dielectric permittivity of NaYCuTiO ceramics reaches values larger than 10 at room temperature and 1 kHz. Moreover, these ceramics exhibit two distinct thermally induced dielectric relaxations over a broad temperature range. The loss tangent is indeed small, ~0.032-0.035. At low temperatures, dielectric relaxation was attributed to the oxygen vacancy effect, while at high temperatures, it was attributed to grain boundary and sample-electrode contact effects. Our calculations revealed that Y and Na ions are likely to occupy Ca and Cu sites, respectively. As a result, other Cu related phases, especially CuO, were observed at the grain boundaries. Based on our analysis, there is a charge compensation between Na and Y ions in NaYCuTiO. Additionally, the Cu and Ti states observed in our XPS study originate from the presence of an oxygen vacancy in the lattice. Last, the primary cause of the enormous dielectric permittivity of NaYCuTiO ceramics primarily comes from the internal barrier layer capacitor effect.