TITLE: Influence of Dopants in Reducing Contact Resistance in PTCR Thermistors
AUTHOR: Rishi Shukla
SCHOOL: North Attleboro High School
SCHOOL ADDRESS: Landry Avenue, North Attleboro, MA 02760

For many years, PTCR Thermistors have been used to prevent power surges from negatively affecting various electronic devices. From radios to airplanes, these thermistors have provided years of protection. Barium titanate based PTCR thermistors are doped with lanthanum or yttrium ions in order to provide free electrons. The insertions are made during the actual production of the thermistor. Silver coating is commonly used to provide the thermistor which highly conductive material. In this experiment, the silver coating was complimented with additions of indium-gallium, aluminum, and tin by means of screen printing. These insertions were made to study the influence of these dopants in reducing barrier contact resistance between thick-film silver paste and barium titanate. Results indicate that an addition of 10% indium-gallium composition effectively reduces the contact resistance between silver and barium-titanate. These results could lead to the development of a replacement for the highly dangerous aluminum flame spraying process commonly used in the industrial world.