Effect of Spark Plasma Sintering Current and Voltage on the Microstructure and Electrical Properties of Borosilicate Glass–Indium Tin Oxide Composites

Borosilicate glass–indium tin oxide (ITO) composites made from glass microspheres and ITO nanoparticles provide a unique model system to monitor the effect of spark plasma sintering (SPS) parameters on the resultant electrical properties of the composites. Composite sets containing different ITO content (up to 10 phr), fabricated under the same SPS conditions, are used as the starting point for the equivalent circuit analysis. The effect of changing the various SPS parameters such as heating rate, hold temperature, and applied pressure on the current and voltage profiles experienced by samples containing 2.5 phr (2.44 wt%) ITO, and their resultant electrical response are reported. Experiments are carried out varying a single SPS parameter at a time while keeping others constant. The applied pressures used range from 5 to 40 MPa; the hold temperature is varied from 610 to 680 °C; and the heating rate is tested between 2 and 200 °C min⁻¹. It is demonstrated that not only do the current and voltage profiles change in all of these instances but also the microstructure and resultant electrical properties of the composite samples being fabricated. Results indicate that all of these parameters are interdependent and can affect the electrical properties of the fabricated samples by many orders of magnitude in some cases.