SYNTHESIS OF DIELECTRIC MATERIALS CaCu3Ti4-xMxO12 (M= Zr4+ AND Nb5+,Y3+) BY MEANS OF SOLID STATE REACTION METHOD

• Main Author: DAMA YANTI (NIM : 20514019), DEMI
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/21635
• Institution: Institut Teknologi Bandung

Ceramic materials with good dielectric properties are desirable for many electronic applications such as energy storage device, insulator, filter and telecommunication systems. CaCu3Ti4O12 have been reported in recent years as one of the ceramic materials with extraordianary dielectric properties. CaCu3Ti4O12 perovskite posseses a giant dielectric constant and has good stability at high temperature range. The dielectric constant depends strongly on the frequency of external field, defects of material, and temperature. The addition of dopants can increase the dielectric constant, decrease the dielectric loss, and enhance the temperature stability of dielectric materials. In this work, CaCu3Ti4xMxO12 (M = Nb5+,Y3+ and Zr4+) have been studied. CaCu3Ti4O12 co-doped with Nb,Y and doped with Zr were synthesized by means of solid state reaction method. The precursor mixtures with stoichiometric ratio were thoroughly ground for 6 h together using agate mortar and pestle then were calcined at 800 0C in furnace box for 12 h. The calcined mixtures were reground for 3 h and pressed in to disk shaped pellets then sintered repeatedly at 1000 0C for 4 h, 1000 0C for 4 h, and then at 950 0C for 4 h. The sintered pellets were cooled down in the furnace to room temperature then were polished and coated with silver paste on the both sides as electrodes. The structural, microstructure and dielectric properties of CaCu3Ti4O12 were investigated by XRD, XRF, SEM and LCR meter. XRD pattern showed the characteristic peaks of CaCu3Ti4O12 and the peaks are well consistent with JCPDS Card No. 75-2188. The secondary phase of starting materials of CuO and TiO2 were observed with small intensities. The presence of CuO and TiO2 residues in the samples indicate a lack of mixing and grinding time of the precursor and incomplete calcination process. No secondary phase Nb2O5, Y2O3 and ZrO2 were observed, indicating that Nb,Y and Zr have successfully substituted Ti atom in CaCu3Ti4O12. The peaks shift toward lower 2θ values as Nb,Y co-doped and Zr-doped CaCu3Ti4O12 indicating an increase in the lattice constant of cubic phase CaCu3Ti4O12. The increased lattice constant can be attributed to the larger ionic radius of Nb5+, Y3+ and Zr4+ than Ti4+. Zr-doped CaCu3Ti4O12 show the biggest lattice constant although Y3+ have larger ionic radius than Zr4+. XRF analysis show the presents of Ca, Cu, Ti, Nb, and Y for sample CaCu3Ti4O12 co-doped by Nb,Y. XRF analysis for sample Zr-doped CaCu3Ti4O12 show the presents of Ca, Cu, Ti, Zr. SEM micrographs show microstructure of undoped and doped CaCu3Ti4O12 pellets. The dense microstructures were obtained in all samples and the structure were cubic. The Nb,Y co-doped CaCu3Ti4O12 sample show less dense and smaller in particles size compared to Zr-doped and undoped CaCu3Ti4O12. Dielectric properties were observed using Agilent E4980A precision LCR meter at frequency range of 20Hz - 2MHz and temperature range from room temperature to 200 0C. The dielectric constant value of Nb,Y co-doped CaCu3Ti4O12 is very high at 20Hz which is about 2,05x104 for temperature 125 0C. Zr-doped and undoped CaCu3Ti4O12 show dielectric constant which is about 5.38x103 and 4,27x103, respectively. Nb,Y codoped CaCu3Ti4O12 also has a high dielectric loss which is about 632, while Zrdoped and undoped CaCu3Ti4O12 have lower dielectric loss of 3,74 and 2,82 respectively. Nb,Y co-doped can increase the dielectric constant and the temperature stability of CaCu3Ti4O12