Search of Potential Dopants and its Effect on TiO2-Based Low Voltage Varistor Materials

• Main Authors: Begum S., Kothandapani Z., Hashmi M.S.J.
• Other Authors: 57216608034
• Format: Book chapter
• Published: Elsevier 2024
• Subjects: Dielectric strength; Dopants; Fired density; Green density; Nonlinear coefficient; Performance characteristics; TiO₂ varistor
• Institution: Universiti Tenaga Nasional

Varistors are electroceramic devices used as surge protectors for electrical and electronic systems. At present low-voltage varistors are in demand due to miniaturization of the microelectronic circuits. In this research, the electrical properties of titanium dioxide (TiO2) doped with tantalum pentoxide (Ta2O5), tungsten trioxide (WO3), silicon dioxide (SiO2) and bismuth oxide (Bi2O3) and fired at different temperatures were investigated for low voltage applications. The adequate amount of dopants at suitable sintering temperature had beneficial effect in improving the properties of TiO2. High green and fired density, high Vickers hardness and compressive strength were achieved with the composition of 0.5% SiO2, 0.5% Ta2O5, 0.25% WO3, and 0.5% Bi2O3 when sintered at 1400�C. The average grain size was also increased with the dopants system and significantly lowered the breakdown voltage (910 mV/mm), making it suitable for low voltage application. Furthermore, the current-voltage characteristic of the TiO2 revealed a significantly high value of nonlinearity of 16.5 and low clamping ratio. Moreover, higher permittivity of 4.89�104 and low dissipation factor at 100 Hz were achieved with the new composition. Hence, it was possible to produce a new TiO2 based varistor material with enhanced properties and reliability. The fabrication was simulated using Silvaco software which showed higher value of 21.4 for the nonlinear coefficient with the same composition. The composition of 0.5 wt% Ta2O5+0.5 wt% SiO2+0.25 wt% WO3+0.5 wt% Bi2O3 when sintered at 1400 �C with two hours of holding time provided significantly improved characteristics. � 2023 Elsevier Inc. All rights reserved