Siam Physics Congress 2015

Giant Dielectric Permittivity and Low Dielectric Loss Tangent in Yb-doped CaCu${}_3$Ti${}_4$O${}_{12}$ Ceramics

20 May 2015, 14:45

15m

Phokheetara Grand Ballroom

Oral presentation Material Physics, Nanoscale Physics and Nanotechnology Material Physics, Nanoscale Physics and Nanotechnology

Speaker

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

Description

In this research work, the giant dielectric response in Ca${}_{1-3x/2}$Yb${}_x$Cu${}_3$Ti${}_4$O${}_{12}$ ($x$ = 0, 0.05, 0.15) ceramics prepared by a modified sol-gel method and sintered at 1100 ${}^{\circ}$C for 6 and 12 h were investigated as functions of temperature and frequency. A single phase of CaCu${}_3$Ti${}_4$O${}_{12}$ was obtained in all ceramic samples. Grain growth of Ca${}_{1-3x/2}$Yb${}_x$Cu${}_3$Ti${}_4$O${}_{12}$ ceramics was effectively inhibited by Yb${}^{3+}$ doping ions, which can be explained to the effect of solute drag of Yb${}^{3+}$ doping ions. High dielectric permittivity ($\sim$10${}^4$) and very low loss tangent ($\sim$0.01$-$0.02) at 1 kHz with good temperature stability of ${\varepsilon}^{\prime}$ ranging from -55 to 125 ${}^{\circ}$C were achieved in a Ca${}_{0.925}$Yb${}_{0.05}$Cu${}_3$Ti${}_4$O${}_{12}$ ceramic. Furthermore, the dielectric permittivity was found to be nearly independent of frequency (10${}^2 -$10${}^6$ Hz) and dc bias voltage (0$-$40 V). Interestingly, the grain boundary resistances of Ca${}_{1-3x/2}$Yb${}_x$Cu${}_3$Ti${}_4$O${}_{12}$ ceramics at room temperature were calculated from the activation energies and found to be $\sim$0.7$-$12.5 G$\Omega$.cm. The effect of annealing in O${}_2$ atmosphere on the dielectric properties was also investigated. It was suggested that variations in dielectric properties of Ca${}_{1-3x/2}$Yb${}_x$Cu${}_3$Ti${}_4$O${}_{12}$ ceramics due to Yb${}^{3+}$ substitution and annealing were associated with the electrical response at grain boundaries.