Effects of Mg2ti03 (Mt) addition on dielectric properties of CaCu3Ti40i2 (CCTO) / Shaidatul Fahana Tajuddin
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This project studied the effect of MgTi03 (MT) addition on CaCu3Ti40i2 (CCTO). Recently an oxide ceramic CCTO was reported that exhibits very high dielectric constant value, which is desirable for many microelectric applications. However, the dielectric loss of the material is relatively and become less useable. Therefore, in this work, CCTO is doped with MT in order to lower the dielectric loss. The MT-doped CCTO was prepared by using solid state reaction method. The MT doped with CCTO, calcining at 1000°C for 12 hours and sintered at 1100°C for 24 hours. Effect of MT dopant to the dielectric properties of CCTO had been studied. The high dielectric constant and low dielectric loss was observed at 0.1, and 0.2 MT dopant compared from its pure samples (X= 0). However for 0.3 MT dopant was dropped from high value of dielectric constant to the lowest value and result in high dielectric loss. Over the wide frequency range, 0.1 MT was more stable then other samples that always present high dielectric constant and low dielectric constant compared with undoped CCTO and other sample. This result indicates that certain MT dopant can be used to improve the dielectric properties of CCTO.Keywords:
Dielectric loss
High-κ dielectric
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The properties of undoped and Mg-doped CaCu 3 Ti 4 O 12 (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 Ca 1-x Mg x Cu 3 Ti 4 O 12 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 Ca 1-x Mg x Cu 3 Ti 4 O 12 ceramics with x = 0.10 at the same frequency range. The results indicate that Mg ions have effectively changed the properties of CCTO.
Dielectric loss
Lattice constant
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ZnO-B2O3(ZB) doped CaCu3Ti4O12(CCTO) ceramics were prepared by solid-state reaction,from the mixture of ZB and CCTO powder calcined at 1 100 ℃.The effects of ZB on the microstructure and dielectric properties of CCTO ceramics were investigated.And the dielectric mechanism with giant dielectric constant was also analyzed.The results show that CCTO ceramics with a small amount of ZB additive(w≤2%,mass fraction) is of single CCTO phase with BCC perovskite structure.Zn2TiO4 phase is detected when w is above 2%.For the CCTO ceramics with w=0.5% and 10%,the dielectric constant is enhanced obviously,while the dielectric loss is higher than that of CCTO.On the other hand,for the CCTO ceramics with 1%-5% ZB additions,the dielectric constant is nearly independent of ZB content and frequency.And they exhibit low dielectric loss and good thermal stability.Especially,CCTO ceramics with 2% ZB exhibit the excellent dielectric properties: relative dielectric constant er=336,dielectric loss tan δ=0.018,temperature coefficient of dielectric constant τe=-1.5×10-5 ℃-1.The impedance spectra of the ZB-doped CCTO ceramics indicate that CCTO ceramics consist of semiconducting grain boundaries and insulating grains,which results in the giant dielectric constant of CCTO ceramics.
Dielectric loss
High-κ dielectric
Temperature coefficient
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The doping effects of (Ba0.6Sr0.4)TiO3 (BST) on dielectric properties of CaCu3Ti4O12 (CCTO) ceramics were identified. As an oxide ceramics that exhibit very large dielectric constant, the CCTO ceramic had became more favourable than the common ferroelectric materials. Its broad application in various electronic devices had recently attracted strong scientific interests. However, such material also undesirably displayed relatively high in dielectric loss making it is quite unusable. Therefore, the doping process of BST was aimed to reduce the dielectric loss of CCTO. The ceramics were prepared by solid-state reaction method and undergone sintering process at 1100°C for 12 hours. Three sample characterizations were done including X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Electrical Impedance Spectroscopy (EIS) measurements. The variation of dielectric constant with dopant composition is explained by the Lichtenecker's logarithmic law as the samples show decreasing trends of dielectric constant with increase of BST. According to the IBLC model, successful reduction in dielectric loss of CCTO is attributed to the increase of grain boundary resistivity with increase of BST. Over the dopant compositions, the optimum volume ratio for large dielectric constant is found in the x=0.3 sample while x=0.4 sample exhibit very low dielectric loss of CCTO. Thus this indicates that certain BST dopant can be successfully used to improve the dielectric properties of CCTO.
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High-κ dielectric
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Dielectric loss
Dissipation factor
High-κ dielectric
Phase boundary
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Dielectric loss
Diffractometer
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Undoped and Al-doped CaCu 3 Ti 4 O 12 Ceramics (CCTO) ceramics were prepared by the coprecipitation method, and the electric and dielectric properties were investigated. The concentration of Al-doped in CCTO influenced the electric and dielectric properties. Through adjusting the concentration of Al-doped, we obtained polycrystalline ceramics samples with the improved properties of dielectric loss and high dielectric permittivity over the wide frequency range. The results indicated that a high dielectric constant and low dielectric loss can be achieved by Al 3+ substitution for Ti 4+ , because the Al-doped CCTO could enhanced the grain boundary resistivity, and the optimum doping concentration is about x=0.3. With x=0.3 Al doping, the dielectric constant was 16000 at 1 kHz and the loss value was below 0.1 over the frequency range of 10 2 Hz to 10 4 Hz.
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Dielectric strength
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CaCu 3 Ti 4 O 12 (CCTO) exhibiting high dielectric constants has recently attracted considerable attention because of the high dielectric constant of about 10 5 at radio frequency and good temperature stability over a wide temperature range. But high dielectric loss and low breakdown strength seriously affect its application. B 2 O 3 is chosen as glassy phase and it can make grain grow rapidly and decrease the sintering temperature. Meanwhile, B 2 O 3 can improve the breakdown strength of CCTO and decrease dielectric loss due to the increase of the density. It can be observed that B 2 O 3 precipitate in grain boundaries and increase the resistance of grain boundary. The main CaCu 3 Ti 4 O 12 phase was confirmed by X-ray diffraction, the microstructure with obvious grain and grain boundary structures was observed by scanning electron microscopy. This study indicates that the amount of B 2 O 3 can increase the dielectric constant of CCTO keeping 10 4 in the frequency range from 10 −1 Hz to 10 6 Hz and can also decrease the dielectric loss of CCTO since it can increase the resistance of the grain boundary. For the sample doped with 3 wt % B 2 O 3 , its dielectric constant is stable from 10 −1 Hz to 10 6 Hz, the tanδ decrease to 0.06 compared with 0.7 at 1 kHz of the undoped CCTO sample, and its grain boundary resistance is obvious much bigger than other samples.
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