Optimizing Bi2O3 and TiO2 to achieve the maximum non-linear electrical property of ZnO low voltage varistor.
BACKGROUND
In fabrication of ZnO-based low voltage varistor, Bi2O3 and TiO2 have been used as former and grain growth enhancer factors respectively. Therefore, the molar ratio of the factors is quit important in the fabrication. In this paper, modeling and optimization of Bi2O3 and TiO2 was carried out by response surface methodology to achieve maximized electrical properties. The fabrication was planned by central composite design using two variables and one response. To obtain actual responses, the design was performed in laboratory by the conventional methods of ceramics fabrication. The actual responses were fitted into a valid second order algebraic polynomial equation. Then the quadratic model was suggested by response surface methodology. The model was validated by analysis of variance which provided several evidences such as high F-value (153.6), very low P-value (<0.0001), adjusted R-squared (0.985) and predicted R-squared (0.947). Moreover, the lack of fit was not significant which means the model was significant.


RESULTS
The model tracked the optimum of the additives in the design by using three dimension surface plots. In the optimum condition, the molars ratio of Bi2O3 and TiO2 were obtained in a surface area around 1.25 point that maximized the nonlinear coefficient around 20 point. Moreover, the model predicted the optimum amount of the additives in desirable condition. In this case, the condition included minimum standard error (0.35) and maximum nonlinearity (20.03), while molar ratio of Bi2O3 (1.24 mol%) and TiO2 (1.27 mol%) was in range. The condition as a solution was tested by further experiments for confirmation. As the experimental results showed, the obtained value of the non-linearity, 21.6, was quite close to the predicted model.


CONCLUSIONS
Response surface methodology has been successful for modeling and optimizing the additives such as Bi2O3 and TiO2 of ZnO-based low voltage varistor to achieve maximized non-linearity properties.
Material Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Yadollah
Y
Abdollahi
Material Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Azmi
A
Zakaria
Department of Physics, Faculty Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Raba'ah Syahidah
RS
Aziz
Department of Physics, Faculty Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Siti Norazilah Ahmad
SN
Tamili
Material Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Khamirul Amin
KA
Matori
Department of Physics, Faculty Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Nuraine Mariana Mohd
NM
Shahrani
Department of Physics, Faculty Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Nurhidayati Mohd
NM
Sidek
Material Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Masoumeh
M
Dorraj
Department of Physics, Faculty Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
Seyedehmaryam
S
Moosavi
Bi2O3; Modeling; Optimization; RSM; TiO2; ZnO-varistor