A detailed study on the dielectric properties of CCTO@SiO2 core-shell nanoparticles: Role of SiO2-NH2 shell over CCTO core surface

摘要

In this work amine functionalized core-shell CCTO silica NPs (CCTO@SiO2-NH2) have been designed with dielectric gradients. CCTO@SiO2-NH2 core-shell NPs consist of CCTO as core (dia. 100-300 nm), and aminated silica as a shell of thickness from 5 nm-20 run. CCTO@SiO2-NH2 core/shell NPs were characterized with suitable characterization tools and the dielectric bahaviours were measured through impedance measurement. The dielectric study has shown significantly high dielectric properties at sintered temperature 1000 degrees C (6 h). Further, with the increase in the shell thickness of coated SiO2-NH2 on CCTO core, the dielectric constant e', as well as the dielectric loss epsilon '' values decreased at respective frequencies, ranges between 20 Hz and 2 MHz and vice versa. The study also suggests that at the lowest frequency of 20 Hz, CCTO@SiO2 NPs with a thickness of 5 nm shows a relatively high c' 1.390 x 10(3) whereas of 20 nm shell thickness shows a epsilon' value of 1.39 x 10(2). However, with a change in the thickness of SiO2 shell, the values of epsilon' and epsilon '' varied with a regular trend (2 Hz to 20 MHz). The thinner and thicker coated SiO2 on CCTO NPs exhibited epsilon '' of (2.7 x 10(2), 13) and (73, a negative value of -26) at 1 kHz and 2 MHz, respectively. Thus the values of epsilon' as a function of frequency for CCTO@SiO2-NH2 core/shell NPs at different temperature range between RT to 250 degrees C signifies the high epsilon' 1.2 x 10(4) for least coating and when coated sample undergoes heat treatment, it leads to the removal of some organic group before 150 degrees C which contributes to the increase of epsilon' due to the property showing by CCTO surface towards the externally applied field. Finally, it can conclude that this series of CCTO@SiO2-NH2 with a different dielectric constant can be used for designing various electronic devices.