Effect of ceramics/polymer heterointerface on dielectric property of self-assembled BaTiO₃/poly-L-lactic acid composite materials

The dispersion state of barium titanate (BT) particle groups in self-assembled BT/poly-L-lactic-acid (PLLA) composites prepared under different fabrication conditions was investigated. In particular, the BT/PLLA/BT heterointerface in the BT aggregates by the self-assembly process was analyzed and the effect of the BT/PLLA/ BT heterointerface and the BT/BT interface on the dielectric properties of BT/PLLA composites were investigated. BT/PLLA composites were fabricated by adding BT particles and BT granules with low and high-speed kneading conditions. The volume fraction of BT in composites varied from 5 to 20 vol.%. The BT aggregates having a BT/PLLA/BT heterointerface were formed under the low-speed kneading condition and the BT agglomerates having a BT/BT interface were formed under the high-speed kneading condition within the self-assembly process. The tan ¤ of the BT/PLLA composite of self-assembled BT aggregates having the BT/PLLA/ BT heterointerface was lower than that of the BT granules having the BT/BT interface. The dielectric constant (¾¤) of the self-assembled composite was increased by growing an average secondary particle area of BT fillers. In contrast, the average secondary particle area of BT granules was increased, as compared with 5 vol.% of BT. However, the change in ¾¤ was saturated. The slopes of the change in the ¾¤ depending on the secondary particle area of BT fillers were different between the self-assembled BT aggregates having the BT/PLLA/BT heterointerface and the BT granules having the BT/BT interface. Thus, it was suggested that it was an important role in improving the dielectric properties to form ceramic secondary particle groups having the ceramics/polymer/ceramics heterointerface by the self-assembly process.