Fabrication of Conductive Glass Nanocomposites with Networks of Antimony Tin Oxide
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Fabrication of Conductive Glass Nanocomposites with Networks of Antimony Tin Oxide Timothy L. Pruyn1 and Rosario A. Gerhardt1 1 School of Materials Science and Engineering, Georgia Institute of Technology Atlanta, GA 30332-0245, U.S.A. ABSTRACT The percolation threshold in a ceramic composite depends on the processing conditions used to fabricate them along with the size and shape of the filler. In this study, borosilicate glass microspheres were used as the matrix material and nanosized antimony tin oxide (ATO) particles were used as the filler. The microsphere/ATO composites were fabricated by hot pressing around the glass transition temperature in order to control the viscosity. The pressure and temperature applied allowed the ATO to be confined to the spaces between certain glass particles, forming percolating networks at low volume fractions of the ATO. The electrical properties were examined using ac impedance spectroscopy. The impedance, electric modulus, and tan į were studied which allowed for valuable insights in structure-property-processing relationships in these materials, along with determination of the percolation behavior in these composites. This analysis on samples right before percolation indicated that there was a highly resistive component affecting long range conductivity which is likely due to porosity at the triple points while the dielectric response is affected by the clusters of ATO nanoparticles. Based on this, the percolation of ATO should reduce down to lower concentrations if the processing conditions are improved to reduce this porosity and further segregate the ATO. INTRODUCTION Composites containing an insulating and a conducting phase can exhibit a wide range in properties due to the various interactions that can take place in these composites[1,2]. The purpose of this study is to create segregated percolated networks of electrically conductive ATO inside a glass matrix. This would potentially result in multifunctional composites that retain many of the properties of the glass, but improve other properties such as the electrical conductivity. The creation of segregated networks results in low percolation thresholds since the material is confined to certain regions of the composite so there is a greater chance for interparticle filler contact at lower volume fraction of material, unlike random networks which require a high amount of filler[3,4]. Typically, glass is not produced through a powder route but this method is needed to achieve the highest amount of filler segregation. By adjusting the particle size ratio between the glass and filler, the distribution of filler can be controlled to be either random or segregated[3-5]. If the matrix particles are much larger than the filler, then there is an excluded volume in which the filler particles can occupy so the filler connects between the larger particles and percolates. Further segregation can occur by controlling the viscosity of the glass such that it is high enough that it will push the conductive filler to the interfaces betwe
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