Study Of The Fabrication And Organization Properties Of Copper-Based Ba_1-xSr_xTiO₃ Composites

Barium strontium titanate ceramic particles which have negative thermal expansion properties when it reaches the Curie temperature are choosen as the reinforcement and copper which have high heat conductivity are choosen as matrix of composites. Different content of strontium in barium strontium titanate ceramic particles reinforced copper matrix composites are prepared by Spark Plasma Sintering for electronic packaging applications. And the composites were annealed. Using the methods of microstructure analysis(XRD, SEM, OM, etc.) to observe the morphology of reinforcement and matrix in composites, interfacial characteristics. Using thermal expansion instrument and thermal conductivity equipment to test and analyse the thermal expansion and thermal conductive ability of the composites. Using Intelligent resistance tester to test the conductivity of the composites.XRD and microstructure observation results show that the reinforcement of SBT can be prepared by solid phase synthesis and the SBT are uniformly dispersed in the SBT/Cu composites. The densification of the composites is very high. With the content of strontium increasing, the Curie temperature of the SBT is decreasing. The phase of the SBT will change from the tetragonal phase to cubic phase.The reinforcement of SBT in the SBT/Cu composites is keeping change phase when the temperature is between 30 and 300?.When the temperature is 250?, the phase change is caused by the internal stress changing and the CTE of the SBT/Cu composites decreases. The thermal expansion coefficient is not stable, but it can be stabilized with proper heat treatment process. The electronic conductivities of the SBT/Cu composites is influenced by the poor thermal conductivity of the reinforcement of SBT, the scattering of the heat by the hole, the dislocations and twins. The conductivity of the composite is about 30% of copper, which is due to the poor conductivity of the reinforcement of SBT and the electronic scattering effect by the internal defects of the composite.The thermal expansion coefficient of the composite is influenced by the annealing temperature and the annealing time. The thermal expansion coefficient of the composite is the lowest when the temperature is 300? and the time is 2H. In the whole temperature range, the reinforcement of SBT in the SBT/Cu composites is keeping change phase.