Siam Physics Congress 2015

Effects of Oxygen Vacancies on Dielectric Properties of Na${}_{1/2}$Bi${}_{1/2}$Cu${}_3$Ti${}_4$O${}_{12}$ Ceramics Prepared by a Urea Combustion Method

21 May 2015, 13:00

3h 30m

Board: MNA-11

Poster presentation Material Physics, Nanoscale Physics and Nanotechnology Poster-3

Speaker

Mr Wattana Tuichai (Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen University, Khon Kaen, THAILAND 40002)

Description

The influences of oxygen vacancies on the dielectric and electrical properties of Na${}_{1/2}$Bi${}_{1/2}$Cu${}_3$Ti${}_4$O${}_{12}$ ceramics prepared by a urea combustion method were investigated via annealing in oxidizing atmosphere. Interestingly, a single Na${}_{1/2}$Bi${}_{1/2}$Cu${}_3$Ti${}_4$O${}_{12}$ phase was successfully prepared using a low calcination temperature of 800 ${}^{\circ}$C for 6 h. High dielectric permittivity (${\varepsilon}^{\prime}$) and dense ceramic microstructure were achieved by sintering at a low temperature of 980 ${}^{\circ}$C. The values of ${\varepsilon}^{\prime}$ and tan$\delta$ were reduced by annealing in O${}_2$ atmosphere, which were described to correlate with the decrease in oxygen vacancies at grain boundaries. A decrease in low-frequency tan $\delta$ values can be well explained due to the reduction of DC conduction, which was primarily governed by the enhanced grain boundary resistance due to filling oxygen vacancies. A slight decrease in ${\varepsilon}^{\prime}$ due to the annealing process was attributed to the reduction of grain boundary capacitance. By annealing process, the conduction activation energy at the grain boundaries was significantly enhanced, whereas the conduction activation energy inside the grains did not change. The results clearly indicated the effects of oxygen vacancies at the grain boundaries on the giant dielectric response and correlated grain boundary response.