清华大学材料科学与工程研究院《材料科学论坛》学术报告：Understanding, design and control of electrical properties and defect chemistry in electroceramics
报告题目：Understanding, design and control of electrical properties and defect chemistry in electroceramics
报告人：Dr Ming Li（University of Nottingham, UK）
Electroceramics exhibit a wide range of functional properties and find important applications in a vast number of energy and electronics devices, ranging from dielectrics, piezoelectrics and ferroelectrics used in modern electronic devices to pure electronic or ionic conductors and mixed ionic/electronic conductors for applications in fuel cells, batteries, membranes and thermoelectrics. Electroceramics often exhibit complex electrical behaviours involving different types of charge carriers (e.g., electrons, holes, ions) and inhomogeneity in different regions (e.g., grains, grain boundaries, surface layers). Such complex electrical behaviours are associated with defects and low levels of nonstoichiometry induced by impurities in raw materials, deliberate chemical doping or 'accidental' element loss/gain during sample processing.
This presentation starts with a brief overview on the development of BaTiO3-based electroceramics, followed by recent advances in understanding of electrical properties and defect chemistry of Na1/2Bi1/2TiO3. Finally, a new approach is demonstrated to achieve simultaneously enhanced transport properties (oxide ion conductivity and electronic conductivity) and stability in a single-phase mixed ionic-electronic conductor based on perovskite (BiSr)(CoFe)O3 by coupled tuning of bulk and surface chemistry. This presentation will highlight: (i) the challenges in measuring the electrical properties, interpreting the data and understanding the electrical conduction mechanisms in electroceramics; and (ii) the crucial importance of such understanding to design new materials and improve the performance of existing materials.
Dr Ming Li obtained his PhD in 2008 from the Department of Materials Science and Engineering, University of Sheffield under the supervision of Professor Derek Sinclair. Upon completing his PhD, he remained in the Sinclair group working as a Post-Doctoral Research Associate (PDRA) until March 2013. He then worked with Professor Matthew Rosseinsky FRS as a PDRA in the Department of Chemistry at the University of Liverpool before starting his independent academic career at the University of Nottingham in September 2014.
Dr Li specialises in probing electrical conduction mechanisms and defect chemistry of electroceramics using a variety of electrical characterisation techniques, particularly Impedance Spectroscopy. This approach enables deep understanding of composition-structure-property relationships in electroceramics. His current research focuses on designing new energy/electronic materials, including dielectric, ferroelectric, piezoelectric materials for applications in modern electronic devices as well as pure electronic or ionic conductors and mixed ionic-electronic conductors for applications in solid oxide fuel cells, oxygen separation membranes and thermoelectrics. He has published over 50 papers in Nature Mater., Adv. Mater., Chem. Mater., Appl. Phys. Lett., J. Am. Ceram. Soc., etc.