Abstract
Thermal expansion causes problems in semiconductor industry and optical communications where precise positioning is required. There are a few materials that show negative thermal expansion (NTE). It was recently found that perovskite Bi1−xLaxNiO3 and BiNi1−xFexO3 show giant NTE around room temperature. In this study, the effect of these NTE materials as filler on the thermal expansion of epoxy resin was investigated. Bi0.95La0.05NiO3 and BiNi0.85Fe0.15O3 powders were prepared by high-pressure synthesis at 6 GPa and 1000 ˚C and were dispersed as filler in a liquid epoxy resin followed by curing for 1 hour at 150 ˚C to form composites. Structural transition of the filler materials as an origin of NTE was confirmed by XRD measurement. The thermal expansion was evaluated by thermal mechanical analyzer (TMA) and strain gauge measurements. The structural phase transitions of the fillers from the triclinic low-temperature to orthorhombic high-temperature phases were confirmed by the temperature variation of XRD patterns. The dilatometric curve showed plateaus owing to the NTE of fillers. It should be noted that, the linear thermal expansion coefficient of 21 vol% BiNi0.85Fe0.15O3/epoxy resin composite was negative (～− 14 ppm/K) between 300 and 310 K.
