The Investigation On The Preperation Of Calcium Copper Titanate(CaCu₃Ti₄O₁₂) Fibers And Organic Composite Films

The high dielectric constant materials have been used widely in the microelectronics industry because of the miniaturization and integration of microelectronic devices, which have significant applications in the large-capacity capacitor and dynamic random access memory(DRAM). The traditional ferroelectric materials such as BaTi O3 etc. are the commonly high dielectric constant materials. However, this kind of materials have ferroelectricity、relaxation and structural change, thus making the dielectric constant more sensitive to the changes of temperature, which could reduce the stability of devices. In recent years, the CaCu3Ti4O12(CCTO) with a cubic perovskite structure attracts more attention because of its giant dielectric properties which dielectric constant is exceed 104 at room temperature, in addition, it is stability for the changes of temperature. However, the high dielectric loss restricts the practical applications. Thus, it is more important to find an effectively way to decrease the dielectric loss of CCTO.The internal barrier layer capacitor(IBLC) model has been generally accepted describing that the CCTO is made of the series parallel small-capacity capacitors which come from the conductive grains and insulating grain boundaries. It is found that the dielectric loss can be significantly reduced by increasing the grain boundary resistance of CCTO. So that the organic macromolecule polymer with high insulation resistance and low dielectric loss can be used to mix with the CCTO, having been a popular study point. We have did following contents for the researching of CCTO fibers and mixing with the organic macromolecule polymer:(1)First of all, we have did some research about the influence factors of electrospinning nanofibers with polyvinylpyrrolidone(PVP) solution. We explore the influence to the microtopography of PVP nanofibers by the PVP concentration, electrostatic spinning distance and spinning voltage etc. In this way, we master the key parameters for preparing the nanofibers.(2) the CCTO nanofibers are synthesised by electrospinning technology. It can be prepared CCTO with good crystallinity and uniform diameter fibers when the PVP content of 35%、the voltage of 12 kV、the distance of 10 cm、the annealing heating rate of 5 ℃/min and the annealing temperature of 900 ℃. The diameter of nanofibers is ~ 100 nm by the scanning electron microscopy analysis, and the result of EDS analysis shows that the atomic ratio of Ca: Cu: Ti: O is close to 1: 3: 4: 12. The TEM characterization shows that the prepared CCTO nanofibers have a single crystal structure, and the grains size are uniform, moreover, the lattice constant is ~7.39?. We calculate the grain size of CCTO is closed to 98.34 nm according to Scherrer formula.(3)we synthesis the CCTO/PVDF composite films. The CCTO nanofibers could be dispersed evenly in the PVDF when CCTO mass fraction is closed to 40%. In this condition, the thickness of the composite films is about 30μm. The characterization of dielectric properties shows that the dielectric constant of CCTO/PVDF composite films is ~ 28 and the dielectric tangent loss is ~ 0.14. Besides, the dielectric constant and loss tagent both tend to decrease with the increasing of frequency. Taken into consideration various factors, the CCTO/PVDF composite films have superior dielectric properties at intermediate and low frequences.