Functional Ceramics Group
About the Group
We are the Functional Ceramics Group in the Department of Metallurgical and Materials Engineering at the Colorado School of Mines, led by Prof. Geoff Brennecka. We work on the fabrication, characterization, and analysis of functional ceramics, primarily advanced dielectrics, ferroelectrics, and piezoelectrics. Check out our Capabilities page for more details, but in general, we make samples via sputtering, chemical solution deposition, and/or any number of powder-based ceramic processing approaches including tape casting and 3d printing. We use a suite of chemical and structural characterization techniques as well as a variety of electrical measurement and analysis tools, both commercial and home-built, to understand fundamental structure-processing-property relationships.
What are Functional Ceramics?
We define functional ceramics as the types of advanced dielectrics, ferroelectrics, piezoelectrics, and related materials whose combined (and often coupled) properties allow them to perform single or multiple functions that other materials simple cannot. Our research focuses primarily on materials that do something interesting in the presence of an electric field, but we are interested in just about anything that has to do with the integration, processing, use, or characterization of ceramics (inorganic, non-metallic solids).
At their most basic, dielectrics are materials that don't conduct electricity, in other words, insulators. Nothing is a perfect insulator, though, and there are many additional functions that dielectrics can perform, ranging from storing charge, energy, and/or information to pulse shaping, filtering, converting,amplifying, rectifying, and just about any other modification you can think of to an electrical or optical signal. Since many ceramics are highly ionic, we are also very interested not only in the effects of our materials on electrical signals but also the effects of electric fields on the materials themselves. This applies during processing (e.g., field-assisted sintering) as well as during operation (e.g., effects of defect chemistry on loss mechanisms, ageing and degradation, and related phenomena). In addition to the behavior of dielectics, we are interested integrating them with materials and processes that will enable them to perform the desired function(s) under desired (and often challenging) operating environments without costing an arm and a leg.
Piezoelectrics are materials that lack a center of symmetry in their crystallographic unit cells such that when a stress is applied to the crystal, the ions displace in a way that leads to a net separation of positive and negative charge centers. This means that not only can the material convert mechanical energy to electrical energy (e.g., stress --> charge), it can also do the converse (e.g., electric field --> strain). An excellent resource for learning more about piezoelectrics is LearnPiezo.
Ferroelectrics are a subset of piezoelectrics (in other words, all ferroelectrics are piezoelectric, but not all piezoelectrics are ferroelectric) that possess a spontaneous polarization at the unit cell level which can be reoriented by application of an electric field. This further increases the various FUNctions that these materials can perform. One of our primary research thrusts is to better understand the dynamic response(s) of ferroelectric materials during this polzarization reorientation (aka switching) process. In fact, better understanding the dynamic responses of all sorts of dielectrics in the presence of electric fields over time frames from nanoseconds to decades is an overarching goal of our group.