Grain-boundary engineering inducing thermal stability, low dielectric loss and high energy storage in Ta plus Ho co-doped TiO2 ceramics

How to achieve a giant dielectric constant and high energy storage density at the same time has been the problem to be solved for donor-acceptor co-doped TiO2 ceramics. In this work, (Ho0.5Ta0.5)(0.01)Ti0.99O2 - x SiO2, where x = 0, 1, 3, 5 and 7 wt% (HTTO - x wt% SiO2), nanocomposites were prepared via a conventional mixed oxide technique. Significantly, the HTTO - 5 wt% SiO2 composite ceramic exhibits a low dielectric loss (tan delta similar to 0.012) and an ultrahigh permittivity (epsilon(r) similar to 1.29 x 104) at 1 kHz. Also, excellent energy storage property with a high breakdown field strength (E-b similar to 1.86 kV/cm) and energy storage density (eta - 1.97 mJ/cm(3)) was obtained in HTTO - 5 wt% SiO2 ceramic. Besides, the enhancement of E-b is attributed to the finer grains and the presence of SiO2 blocking layers in the grain boundaries, which hinder the long-range motion of electrons. It can be concluded that the CP and high energy storage properties arise from the combined contribution of enhanced grain boundary effects and electron-pinning type of defect dipole (EPDD) effects. This study not only proposes an effective method improving E-b, but also offers a new routine for how to simultaneously achieve CP and high eta in TiO2 dielectric materials.

Automated summary

This study successfully achieved a giant dielectric constant and high energy storage density by doping TiO2 ceramics with SiO2 nanoparticles. Notably, the HTTO - 5 wt% SiO2 composite ceramic exhibited low dielectric loss and ultrahigh permittivity at 1 kHz. Additionally, the ceramic showed excellent energy storage properties with high breakdown field strength and energy storage density.