- Economic Impact
- Nano Network
Associate Professor of Materials Science, Oregon State University
Microtechnology-Based Energy and Chemical Systems, Safer Nanomaterials and Nanomanufacturing
High-K Materials Based on Heterogeneous Dielectrics
In this work, the origins of the anomalous high permittivity in the distorted perovskite CaCu3Ti4O12 are being studied with an aim towards engineering the materials for high capacitance density applications. Using a combination of dielectric/impedance spectroscopy, transport measurements, and defect chemistry studies, a working model for the dielectric behavior has been established that relates the observed dielectric response to nanoscale defects.
Furthermore, we have shown that cation doping and glass-ceramic composite microstructures can be used to enhance the high-field dielectric properties with increased insulation resistance and low dielectric loss at frequencies between 100 Hz to 100 KHz.
Lead-free Piezoelectric Materials Based on Bi-Perovskites
Perovskite Pb(Zr,Ti)O3 (PZT) ceramics are widely used for many industrial applications, however there have been environmental concerns with PZT related to the toxicity of lead oxides which are volatile during processing. Consequently, this has motivated the search for lead-free piezoelectric materials with piezoelectric properties comparable to PZT with a reduced environmental impact. We have investigated ceramic solid solutions within the ternary perovskite system Bi(Zn1/2Ti1/2)O3-BiScO3-BaTiO3. With dielectric measurements and polarization hysteresis measurement we are investigating the stability of the ferroelectric phase. With these data, ferroelectric phase diagrams are being derived showing the transition between the pseudo-cubic relaxor behavior of BiScO3 to the tetragonal normal ferroelectric behavior of Bi(Zn1/2Ti1/2)O3-BaTiO3.
Ceramic Heterocontact Chemical Sensors
Research efforts in this area focus on the development of chemical sensors based on ceramic heterocontacts, e.g. n-ZnO/p-CuO. An understanding of the role of transition metal dopants at the heterocontact interface is being pursued through DC transport measurements, AC capacitance measurements, and impedance spectroscopy in a controlled atmosphere furnace at temperatures up to 500°C. Studies of the gas adsorption kinetics through electrical measurements have been used to explain the enhanced sensitivity of Ni- doping.
Novel Ceramic Materials
Additional research efforts in other areas make use of funds from collaborating institutions such as the Korean Advanced Institute for Science and Technology and Chiang Mai University in Thailand in new “exploratory” areas. Recent work includes (i) multiferroic perovskites based on BiFeO3 solid solutions, (ii) the effects of cation ordering in binary and ternary morphotropic phase boundaries in Pb-based ferroelectric systems, (iii) the synthesis of the TiO2 nanofibers via high temperature gas-solid reactions, and (iv) other novel electroceramic materials.