Varistors are the most efficient devices for the protection of power transmission lines and electronic devices against excessive transient surges. The current trends that require varistors with more functions have led to research to develop new ceramic varistor material and titanium dioxide (TiO 2 ) is the emerging new material. In this research nanosized TiO 2 was taken as the base materials to which a small amount of impurities was added as dopants for enhancing the properties. Ta 2 O 5 , WO 3, Bi 2 O 3 and Co 3 O 4 were used as dopants where the percentage of Bi 2 O 3 and Co 3 O 4 was fixed; 0.5% and 0.2% respectively. Samples were prepared with different weight percentages of dopants and sintered at a constant temperature of 1300˚C with 2 hour's holding time to observe the effect of these dopants on physical and mechanical properties of nanosized TiO 2 . Analysis was undertaken to evaluate the properties of the nanosized TiO 2 , such as green density, fired density, fired strength, axial and radial shrinkage. It was found that with the composition of 98.1% TiO 2 +0.7% Ta 2 O 5 +0.5% WO 3 +0.2%Co 3 O 4 +0.5%Bi 2 O 3 have a significant influence on the physical and mechanical properties, which is anticipated to improve the performance of varistor. With the improvement in the physical and mechanical properties of TiO 2 , the composite material has potential application in low voltage application devices.
Development of high performance titanium dioxide (Ti02) based varistor materials demands binders to improve its physical properties which will ultimately enhance its electrical performances. The material used for ceramic based varistor should exhibit good mechanical properties. As for desired mechanical properties, porosity should be minimal, high fued density, high sintered strength and small average grain size are desired. In this paper effect of PV A (binder) on Ti02 was investigated and its influence on physical, mechanical and microstructure was observed. The binder was added during ball milling and then followed by the shaping and sintering process. The samples were characterized by evaluating fued density, hardness, compressive strength and microstructure. Our studies revealed that varistor disc with higher density, hardness and strength can be produced with the use of binder.
Titanium dioxide (TiO 2 ) varistors doped with tungsten oxide (WO 3 ) and bismuth oxide (Bi 2 O 3 ) were investigated. The microstructure and electrical characterization were studied, where the effects of different concentrations of WO 3 and a fixed amount of Bi 2 O 3 were investigated. TiO 2 based varistors have promising potential for the high performance development. The percentage of dopant was varied at various levels and the prepared samples were then characterized by evaluating IV relationships to determine the degree of non-linearity in the varistor. Evaluation was conducted based on non-linear coefficients, breakdown voltage and power loss. Microstructure analysis was also carried out using SEM. The average grain size was determined to find the relationship between microstructure and electrical properties. It was found that a molar concentration with 99.1%TiO 2 . 0.4%WO 3 . 0.5%Bi 2 O 3 yielded the best results in terms of electrical and microstructural properties. The addition of 0.5%Bi 2 O 3 and 0.4%WO 3 creates a relatively low clamping efficiency, higher non-linear coefficient, low breakdown voltage and less power loss.
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