EAGER: Room-Temperature Fabrication of Electroceramics

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Modern electronic circuits contain many kinds of materials, but heating different materials together during processing is difficult due to incompatibilities in chemistry, densification behavior, and/or thermal expansion. High temperatures are typically required, but there is an urgent need for innovative design principles which would allow electroceramics to be processed with organic or semiconductive materials and silver electrodes at temperatures 400°C. The room-temperature fabrication method could be one such technology. Unfortunately, many electrical properties improve only after subsequent heating; thus, the goal of this EArly-concept Grant for Exploratory Research (EAGER) project is to determine the densification mechanisms/kinetics involved and thereby develop room-temperature processable capacitor oxides with useful electrical properties which can be applied throughout the electroceramics industry to lower costs, energy consumption, and consequent greenhouse gas emissions. This research directly supports the continued US competitiveness and supports many commercial defense applications promoting national security. The integration of this research with education will be achieved in several ways, including being included in a Ceramic Processing online graduate course.Co-firing different materials is difficult due to chemical incompatibility at high temperatures as well as differences in sintering behavior and thermal expansion. Due to the slow, thermally-activated diffusional processes, high temperatures are typically required for densification. It is possible to enhance the driving force by the application of pressure during sintering; however, there is an urgent need for innovative design principles which would allow electroceramic compositions to be co-fired with organic or semiconductive structures and silver electrodes at temperatures 400°C. The room-temperature fabrication method could be one such technology, but the physics involved are not yet completely understood, nor are its implications for the properties of functional ceramics. The goal of this project would be to use in situ transmission electron microscopy studies to determine the densification mechanisms/kinetics involved, and in so doing develop a fuller understanding of the mechanisms and kinetics of the room-temperature densification of oxides. With this information, the aim is to develop ultra-low-temperature sinterable capacitor oxides with relative permittivities up to ~200 and loss tangents 0.1 in the radio frequency range. The method involves the use of aqueous solutions as transient solvents to effect densification of ceramic powders via a mediated dissolution–precipitation process. Unfortunately, many dielectric properties improve only after annealing to remove strain, secondary phases, grain boundaries, and point defects which can lead to electron/ion motion. The goal of this research is to develop ceramic dielectric materials which densify at ultra-low temperatures and exhibit the requisite properties for microelectronic applications without any additional thermal processing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.