Preparation And Properties Of CCTO/P(VDF-TrFE) Composites

Polymer based composites with high dielectric constant can be prepared by combining high dielectric constant ceramics and polymer together,which exhibits the advantages of these two kind of materials,such as high dielectric constant,high breakdown strength,light-weight,easy prcessing,good thermal stability.This kind of composites has attract increasing attention due to its excellent overall performance and promising application in microelectronics industry.In this paper,CaCu₃Ti₄O₁₂?CCTO?ceramics were used as the fillers,and P?VDF-TrFE??70/30 mol%?copolymers were used as the matrix materials.CCTO fillers were surface-modified with hydrogen peroxide?H₂O₂?and silane coupling agent Si₆₉,respectively.CCTO/P?VDF-TrFE?composites with different shapes of bulk and thin films were prepared by surface-modified and so on.Firstly,the CCTO fillers were prepared by solid-state reaction method.The effects of CCTO volume fraction,hot-pressing temperature and hot-pressing time on the phase structure,microstructure and dielectric properties of CCTO@H₂O₂/P?VDF-TrFE?bulk composites were studied.Dielectric properties of the CCTO@H₂O₂/P?VDF-TrFE?bulk composites with 50 vol%of CCTO are much better.Compared with different dielectric model of composites,the dielectric constant of CCTO/P?VDF-TrFE?composites at 1kHz could be well predicted by Yamada model.The dielectric constant of CCTO@H₂O₂/P?VDF-TrFE?bulk composites increases with increasing the hot-pressing temperature,and decreases with increasing the hot-pressing time.The best dielectric properties of CCTO@H₂O₂/P?VDF-TrFE?bulk composites at room temperature and 1kHz can be obtained by the hot pressing prcess at140°C for 10 min.??'=26,tan?=0.03?.Secondly,the effects of hot-pressing temperature,CCTO volume fraction and particle sizeonthephasestructure,microstructureanddielectricpropertiesof CCTO@Si₆₉/P?VDF-TrFE?composites were systematically investigated.The effect of hot-pressing temperature on the dielectric properties of CCTO@Si₆₉/P?VDF-TrFE?composites is similar to that of CCTO@H₂O₂/P?VDF-TrFE?bulk composites.The best dielectric properties can be obtained when the composites were hot-pressed at 140°C CCTO@Si₆₉/P?VDF-TrFE?bulk composites with 60vol%CCTO exhibit better dielectric properties.Both of the CCTO@Si₆₉/P?VDF-TrFE?bulk and thin-film composites have better dielectric properties when grain size of CCTO is decreased to 0.5?m.The dielectric constant of CCTO@Si₆₉/P?VDF-TrFE?thin film composite with 60 vol.%CCTO can reach to 50.8 at1 kHz,while The dielectric constant of CCTO@Si₆₉/P?VDF-TrFE?bulk composites with 60vol.%CCTO?prepared at 140°C and 10 min?was 52.2 at 1 kHz.Finally,the interfacial modification mechanism of two surface modifiers(hydrogen peroxide and silane coupling agent Si₆₉)in composites was investigated by using infrared,structural and dielectric properties analysis.The silane coupling agent Si₆₉9 has more significant effect on the dielectric properties of CCTO/P?VDF-TrFE?composites.The dielectric constant of CCTO@Si₆₉/P?VDF-TrFE?thin-film composites at room temperature and 1 kHz is 32.4,while the dielectric constant of CCTO@H₂O₂/P?VDF-TrFE?thin-film composites is 26.4.