|
CaCu3Ti4O12 (CCTO) is a dielectric constant εr up to 104 and has a good temperature stability giant dielectric material, has become in recent years one of the focus of academic attention. However, CCTO has a high dielectric loss (tanδ-0.1), and seriously affect its application. CaCu3Ti4012 ceramic object of study by studying different preparation methods (solid-phase synthesis method, NaCl molten salt method, CaCl2 molten salt method and semi-chemical method), different conditions replaced, bit A, B bit changes CaCu3Ti4O12 ceramic phase structure, microstructure and dielectric properties investigated in order to obtain a high dielectric constant and low dielectric loss, high dielectric material. The main content of the study are as follows: First, the traditional solid phase prepared CCTO ceramic system to study the impact of different process conditions on the CaCu3Ti4O12 ceramic phase structure, microstructure, dielectric properties. The results showed that: when the calcining temperature was 900 ° C, the sintering temperature is 1070-1110 ° C, the ceramic samples were obtained pure perovskite-like structure, and the grain boundary is clear, stomatal less, good density, larger grain size , the grain is full, the average grain size of about 100μm. At this time, when the test frequency of 1 kHz, the ceramic having the best dielectric properties, the dielectric constant of up to 6.14 × 104, the dielectric loss of 0.044; When the test frequency, ceramics could be obtained within the range of 40 Hz-105Hz giant dielectric constant, the dielectric constant is more than 6.0 × 104 and the value of the dielectric loss is less than 0.48. Secondly, the study of the solid-phase method, molten salt method of NaCl, CaCl2 molten salt method and semi-chemical ceramic microstructure of CaCu3Ti4O12, dielectric constant and dielectric loss. The results show that: the solid phase prepared the CCTO ceramic having a greater grain, the clearer the grain boundary of grains tightly packed, dense good. 40-105Hz frequency range, solid-phase method, NaCl molten salt method, semi-chemical prepared CCTO ceramic dielectric constant of more than 104, especially CCTO ceramics prepared by solid-phase dielectric constant up to 6.0 × 104 CCTO ceramic CaCl2 molten salt prepared the permittivity highest value is only 1.5 × 104. -50-55 ° C temperature range of 10 kHz frequency, the dielectric constant of the solid phase prepared CCTO ceramic up to 3.1 × 104, and the dielectric loss is less than 0.04, and also has a good temperature stability; NaCl molten salt method, semi-chemical method of CaCl2 molten salt prepared CCTO ceramic dielectric loss were as high as to 0.12,0.13,0.39. This indicates that the solid phase prepared CCTO ceramic having a high dielectric constant and low dielectric loss. Again, the systematic study of the impact of the the Ti3 content of the CCTO ceramic phase structure, microstructure, dielectric properties and impedance spectroscopy. The results show that: when X LT; 4.00, CaCu3TixO12 appeared in the second phase (Cu2O); obtained when x ≥ 4.00, and a pure phase. According to the results of the SEM and EDX analysis found that when x lt; 4.00, the grain boundary region there are a large number of copper-rich phase (Cu2O). With the increase in the content of Ti, the grain boundary area of ??the copper becomes less and less, and grain boundaries become more and more thin. When x = 4.00, the formation of grain boundaries clear and dense CCTO ceramic. Impedance spectroscopy analysis showed that, with increasing Ti content, the ceramic grain resistance Rg and the grain boundary resistance Rgb first decreases and then increased, when x = 4.00, Rg and Rgb minimum. Dielectric spectrum at room temperature, the dielectric constant of the ceramic (x = 4.00) in the frequency range of 40 Hz-105Hz, more than 5.50 × 104; at 1kHz under the dielectric properties of the ceramic: εr = 6.15x104, tan δ = 0.044. Finally, the system studied Sr content of a Ca1-xSrxCu3Ti4O12 ceramic microstructure, dielectric constant and dielectric loss. When x = 0.10, CSCTO ceramic grain size of max. With the increase of Sr content, CSCTO ceramics at room temperature dielectric constant first increases and then decreases. When x = 0.10, the frequency range of 40 Hz-4.0 × 105 Hz, CSCTO ceramics having a high dielectric constant and low dielectric loss; ceramic dielectric constant and dielectric loss at 1 kHz were 71153 , 0.022; 1 kHz, the dielectric constant of the ceramic CSCTO (x = 0.10) in the temperature range from -50 ℃ -100 ℃ greater than 65000, the dielectric loss is less than 0.05. Meanwhile, it is also systematically study and compare the influence of alkaline earth metal (Mg, Ba, Sr) is substituted Ca0.9A0.1Cu3Ti4O12 ceramic microstructure, dielectric constant and dielectric loss. The study shows that in the frequency range of 40 Hz-105kHz, Ca0.9Sr0.1Cu3Ti4O12 ceramic having greater than Ca0.9Mg0.1Cu3Ti4O12, Ca0.9Ba0.1Cu3Ti4O12, CaCu3Ti4O12 ceramic grains thinner grain boundary, the higher the dielectric The dielectric constant and low dielectric loss. In summary, the use of solid-phase method calcining temperature of 900 ° C, the sintering temperature of 1100 ℃ under the conditions of preparation with excellent electrical properties Ca0.9Sr0.1Cu3Ti4O12 ceramic. The ceramic of Ca0.9Sr0.1Cu3Ti4O12 having the best of the dielectric properties. At 1 kHz than the pure CCTO ceramic compared to the dielectric properties of the ceramic constant from 6.15 × 104 added 7.12 × 104, the dielectric loss is reduced from 0.044 to 0.022, to reduce the object of the ceramic dielectric loss, reduced for further study the CCTO ceramic dielectric loss laid the foundation.
|