Mohd Fariz Ab Rahman

The Effect of MgO Dopant on the Dielectric Properties of CaCu3Ti4O12 Ceramics

The properties of undoped and Mg-doped CaCu3Ti4O12 (CCTO) ceramics have been studied. The samples were calcined at 900°C for 12 hours, and sintered at 1030°C for 10 hours. X-ray diffraction analysis on calcined samples shown the formation of CCTO phase with trace of secondary phases meanwhile completed formation of CCTO single phase obtained for sintered pellets. The peak positions of Mg-doped CCTO were slightly left-shifted from the undoped CCTO, attributed to the lattice expansion. Scanning electron microscopy analysis showed that the grains size becomes larger with the increment of dopant amount. Enhanced dielectric constant was observed in the Ca1-xMgxCu3Ti4O12 ceramics with x = 0.05 for the frequency range from 1 MHz to 1 GHz. The dielectric loss seem to be at lowest value when Ca1-xMgxCu3Ti4O12 ceramics with x = 0.10 at the same frequency range. The results indicate that Mg ions have effectively changed the properties of CCTO.

Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

(1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss w...

Effect of Sintering Heating Rate on CaCu 3 Ti 4 O 12 Formation

CaCu3Ti4O12 (CCTO) is an electroceramic material with complex cubic perovskite-like oxide. It possessed a giant dielectric constant of about 105 over a wide temperature range (100-600 K). In this work, CCTO was synthesized through solid state method. The effect of different heating rate during sintering process was studied. The raw materials - CaCO3, CuO and TiO2 were wet ball milled for 24 hours and calcined at 900 °C for 10 hours. Then the calcined powder was pressed into pellet shape at 300 MPa. Sintering was done at 1040 °C for 12 hours with different heating rates: 3, 5 and 10 °C/min. The phase formation and surface morphology was investigated by X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM), respectively. The density was measured by Archimedes Principle. XRD pattern proves the CCTO single phase formation for the calcined powder and sintered pellet. The SEM images show the different grain size for different heating rate. The density of the pellet was found to be reduced when faster sintering heating rate was used.

Effect of Calcination Temperature on the Breakdown Strength and Energy Density of CaCu 3 Ti 4 O 12 Ceramic

The effect of calcination temperature on the breakdown strength and energy density of CaCu3Ti4O12 (CCTO) ceramics was studied. CCTO ceramics were prepared via solid state reaction method. The raw materials of CCTO were wet mixed for 24 hours and then dried overnight in oven. CCTO mixtures were calcined at three different temperature which is at 900°C, 930°C and 950°C for 12 hours. The calcined powders were compacted at 250 MPa and then were sintered at 1040°C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase and secondary phases of CuO and CaTiO3 for C900 calcined powders but single phase of CCTO was obtained by C930 and C950 calcined powders. Single phase of CCTO also were seen for all sintered samples. Observation on Scanning Electron Microscopy (SEM) micrographs showed large grain size was seen in C900 sintered sample and finer grain size was observed for C930 and C950 sintered samples. C900 sintered sample obtained highest dielectric constant (8617), highest breakdown strength (7.92 kV/cm), highest energy density (2.392 J/cm3).

Dielectric properties of Al2O3/CaCu3Ti4O12 composite at high frequency range

The dielectric properties of CCTO with addition Al2O3 prepared via solid state reaction investigated and reported at 1 GHz. With addition Al2O3 from 20 wt% to 80 wt%, secondary phase starts appear in XRD analysis such as copper dialuminium oxide (CuAl2O4), calcium titanate (CaTiO3) and titanium oxide (TiO2). These secondary phases show great influence on morphology and grain size of Al2O3/ CCTO composites. Hence, the addition of only 20 wt% Al2O3, the dielectric constant of CCTO reduce almost 50% and tangent loss is in between 0.0028 to 0.0630 which is very low and this characterization is suitable to use in electronic application in high frequency range.

Dielectric Properties of CaCu3Ti4O12/Al2O3 Composites

In this work, (1-x)CaCu3Ti4O12/xAl2O3 (x = 0, 0.01, 0.03, 0.05 and 0.1) composite samples were prepared by the conventional solid-state reaction method. The dielectric properties of the samples were investigated at frequency range of 20 – 106 Hz. X-ray diffractogram results show that the samples with Al2O3 sintered at 1040 °C/10 h are mixed phase and consist of CaCu3Ti4O12, CuAl2O4, TiO2 and Al2O3. The average grain size of the samples increased greatly for x = 0.01, then abruptly depressed for x ≥ 0.03. Al2O3-added (x = 0.01) has been shown to increase the dielectric permittivity (ε’) up to ~5000 over frequency range of 102 – 105 Hz, while retaining the dielectric loss (tan δ ~ 0.15) at 1 kHz. With further increase of Al2O3 content, the ε’ and tan δ values of the samples are decreased monotonically in all frequency ranges. The improvement of dielectric properties in the composite sample was attributed to the enhanced grain boundary resistance.

Effect of Glass Addition on the Properties of CaCu3Ti4O12 Ceramics

The effect of glass addition on the properties of CaCu3Ti4O12 (CCTO) ceramics was studied. CCTO ceramics with BaO-SrO-Nb2O5-B2O3-SiO2 (BSNBS) glass additive were prepared using solid state reaction method. The raw materials of CCTO and BSNBS were wet mixed separately for 24 hours, dried overnight and subsequently the BSNBS powders was melted at 1450°C for 2 hours while CCTO powders was calcined at 900°C for 12 hours. BSNBS glass then was grinded to form a fine powders. Different weight percentages of BSNBS powder were added into CCTO and the powders were wet mixed at 24 hours. The mixtures were dried, compacted at 250 MPa and then sintered at 1050°C for 10 hours. X-Ray Diffractometer (XRD) analysis showed the formation of CCTO phase for all sintered samples while secondary phase of CuO phase was identified for sintered BSNBS 1.0 sample. Observation on Scanning Electron Microscopy (SEM) micrographs showed abnormal grain growth was seen in CCTO sample and grain size of the samples become finer with increasing the concentration glass addition. CCTO sample obtained the highest dielectric constant (8670) while the lowest dielectric loss (0.38) was recorded by BSNBS 0.10 sample, measured at 1 MHz.

Dielectric Properties of Mg-Doped CaCu3Ti4O12 Measured at High Frequencies

Mg-doped CaCu3Ti4O12 (CCTO) systems were prepared by solid state reaction using raw materials of CaCO3, CuO, TiO2 and MgO. The samples were calcined at 900°C for 12 hours and sintered at 1030°C for 10 hours. Single phase CCTO formed after sintering process. It was found that dielectric constant and dielectric loss of CCTO improved by MgO dopant.