Abstract:

Donor-acceptor co-doped rutile TiO₂ ceramics with colossal permittivity (CP) have been extensively investigated in recent years due to their potential applications in modern microelectronics. In addition to CP and low dielectric loss, voltage stability is an essential property for CP materials utilized in high-power and high-energy density storage devices. Unfortunately, the voltage stability of CP materials based on co-doped TiO₂ does not catch enough attention. Here, we propose a strategy to enhance the voltage stability of co-doped TiO₂, where different ionic defect clusters are formed by two acceptor ions with different radii to localize free carriers and result in high performance CP materials. The (Ta + Al + La) co-doped TiO₂ ceramic with suitable La/Al ratio exhibits colossal permittivity with excellent temperature stability as well as outstanding dc bias stability. The density functional theory analysis suggests that La³⁺Al³⁺V_O^••Ti³⁺ defect clusters and Ta⁵⁺-Al³⁺ pairs are responsible for the excellent dielectric properties in (Ta + Al + La) co-doped TiO₂. The results and mechanisms presented in this work open up a feasible route to design high performance CP materials via defect engineering.

Key words: Colossal permittivity, Co-doped TiO₂, Defect cluster, Voltage stability