Colossal permittivity and low dielectric loss of Ta5+ and Al3+ co-doped strontium titanate ceramics sintered in N2 atmosphere

In this work, the ceramics of Sr(Ta1/2Al1/2)xTi1-xO3 (x = 0 %, 0.5 %, 1 %, 2 %, 3 %, 4 %, and 5 %) were produced through the solid-state reaction and sintered under N2 atmosphere. The frequency coefficient of permittivity and dielectric loss for the sample with x = 4 % is blow |24%| and |26%|, respectively, within the frequency of 1 kHz to 1 MHz. This demonstrates favorable frequency stability in the dielectric properties. The sample with x = 4 % exhibits remarkable permittivity (εr ∼ 125,000 @ 1 kHz, εr ∼ 95,000 @ 1 MHz) and low dielectric loss (tanδ ∼ 0.054 @ 1 kHz, tanδ ∼ 0.044 @ 1 MHz) were achieved at room temperature. Through the analysis of HAADF-STEM, XPS, it is concluded that and dielectric relaxation, the colossal permittivity effect is primarily attributed to defect clusters associated with oxygen vacancies such as Ti3+ −VO••− Ti3+. The clusters of defect dipoles exert a pinning effect on freedom electrons, constraining their long-range transition and improving the dielectric properties. This study lays the foundation for advancing the electronic components, making a significant milestone in technological advancements.