Microstructure, low loss tangent, and excellent temperature stability of Tb+Sb-doped TiO2 with high dielectric permittivity
Noppakorn Thanamoon, Narong Chanlek, Pairot Moontragoon, Pornjuk Srepusharawoot, Prasit Thongbai
Abstract
The study of colossal permittivity (CP) materials possessing very high dielectric constants (ε′ > 104) has gained traction due to their suitability for application in microelectronic devices, which are evolving rapidly. In addition, the loss tangent (tanδ) and temperature stability of ε′ are crucial factors to consider for actual applications. In this study, (Tb3+/4++Sb5+) co-doped TiO2 (TSTO) ceramic with an appropriate co-dopant content presented an extremely high ε′ value of ∼9.31 × 104 and ultra-low tanδ (∼0.013) at 1 kHz. Moreover, its temperature-dependent coefficient of permittivity deviation (Δε'(T)/ε'30°C) was lower than |±15%| over the temperature range from −60 ℃ to 210 ℃. The TSTO ceramics exhibited highly compact microstructures. The grains, grain boundaries, and microwave dielectric phases (i.e., Tb2Ti2O7) were detected, and their presence is considered to determine the dielectric behavior of the TSTO ceramic. The observation of Ti3+ induced by Sb5+ via X-ray photoelectron spectroscopy explains the appearance of semiconducting grains, as confirmed by impedance spectroscopy (IS). The high resistivity resulting from the grain boundaries and microwave dielectric phase was also confirmed by IS. The findings describe the CP properties of TSTO ceramics via the interfacial polarization process and demonstrate that the existence of microwave dielectric phase particles with appropriate content affects the dielectric relaxation, resulting in the reduction of tanδ.