I-Wei Chen Skirkanich Professor of Materials Innovation 424 LRSM 215.898.5163   iweichen@seas.upenn.edu

Research Interests

Materials science of electronic and structural ceramics including their thin films, heterostructures, and composites. Materials design, synthesis, testing and modeling.

Current Research Projects

Ferroelectric and Magnetoresistive Oxides:
Bulk and thin film ferroelectric, antiferroelectric and magnetoresistive oxides used for memory, sensor and actuator applications are being investigated to understand the roles of domain interfaces, lattice defects, electronic carriers, and structural transitions in their performance. Thin films, oxide-semiconductor heterostructures, single crystals and polycrystals are prepared to conduct model experiments using dielectric, ferroelectric, magnetoresistive, optical, mechanical and scanning-probe spectroscopy. Computer simulation and analytical modeling are also used to gain mechanistic insight of these materials.

Structural Ceramics:
Structural ceramics are widely used today for turbomachinery, cutting tool, and bearing applications. We have developed two novel structural ceramics in recent years. One is a new tough Si-Al-O-N ceramic that can be used as a high temperature hard material. The other is a "ceramic wood" with a wavy multilayer texture that deflects cracks and allows graceful failure. Microstructure control is the key to these developments and the focus of our research.

Nanomaterials and Nanocomposites:
Nanomaterials and their composites often possess unique properties and processing characteristics not seen in ordinary monoliths and composites. We have developed a novel powder processing method which allows nanocrystalline ceramics to sinter without grain growth. We have also prepared a nanocomposite using colloidal and sol-gel chemistry to incorporate proteins and biomolecules into transparent oxide matrices. Applications for sensing, catalysis, bioreactors and optical tagging which exploit the nanosized effects are being explored for these materials.

Selected Publications

• I-Wei Chen and A. Rosenflanz,"A Tough SiAlON Ceramic Based on Alpha Si3N4 with a Whisker-like Microstructure" Nature, 389, 701-04 (1997).
• X-F. Du and I-Wei Chen, "Model Experiments on Fatigue of Pb(Zr0.53Ti0.47)O3 Ferroelectric Thin Films", Appl. Phys. Lett.. 72 [15] 1923-25 (1998).
• I-Wei Chen and Ying Wang, "A Domain Wall Model for Relaxor Ferroelectrics," Ferroelectrics, 206/1-4 & 207/1-2, 245-263 (1998)
• L-L. Wang, T-Y- Tien, and I-Wei Chen, "Morphology of Silicon Nitride Grown from a Liquid Phase," J. Amer. Ceram. Soc. 81 [10] 2677-86 (1998).
• I-Wei Chen, "Structural Origin of Relaxor Ferroelectrics-Revisited," J. Phys. Chem. Solids, 61 [2] 197-208 (1999).
• I-Wei Chen and Y. Wang, "Activation Field and Fatigue of (Pb,La)(Zr,Ti)O3 Thin Films," Appl. Phys. Lett. 75 [26] 4186-88 (1999).
• M. Menon and I-Wei Chen, "Bimaterial Composites via Colloidal Rolling Techniques," J. Amer. Ceram. Soc. 82 [12] 3413-40(1999).
• D-M. Liu and I-Wei Chen, "Encapsulation of Protein Molecules in Transparent Porous Silica Matrices via an Aqueous Colloidal Sol-gel Process," Acta Metar. 47 [18] 4535-44 (1999).
• I-Wei. Chen and X.-H. Wang, "Sintering Dense Nanocrystalline Ceramics without Final- Stage Grain Growth," Nature, 409, 168-71 (2000).