Invited Speaker

Abstract: Development of giant-permittivity and high-tunability dielectric materials has attracted great interest because of growing demand for smaller and faster energy-storage and electronic devices. Materials such as CaCu₃Ti₄O₁₂, displaying the giant dielectric permittivity due to extrinsic Maxwell-Wagner interfacial polarization effect, have previously been reported. Ferroelectric materials possessing intrinsic ionic polarization due to a phase transition to the polar state have also been indicated to possess high dielectric permittivity. Here, a class of the giant-permittivity materials based on SrTiO₃ ceramics doped with about 1% of trivalent ions like yttrium, dysprosium and gadolinium as well as their processing concept, which yields the dielectric permittivity up to ~209 000 at 10 kHz, is reported. The giant permittivity is explained by a coupling of the polar clusters relaxation mode with the donor substitution induced electrons at low temperatures and by the Maxwell-Wagner relaxation around room temperature. Besides the fundamental understanding, this discovery opens a new development window for high-frequency and low-temperature electronic and energy-storage applications.

Keywords: Electroceramics, Doping, Sintering Atmosphere, Polar order, Maxwell-Wagner Polarisation

Biography: Oleksandr Tkach graduated in Microelectronics and Semiconductor Devices by the National Technical University of Ukraine "Kyiv Polytechnic Institute" in 1999. In 2005 he got PhD degree in Materials Science & Engineering from the University of Aveiro, Portugal. After winning a post-doctoral grant to work in University of Porto, Portugal, in 2007 and getting a got post-doctoral contract at the Johannes Gutenberg University of Mainz, Germany, in 2012, he was promoted to Assistant Researcher position at the University of Aveiro in 2014. For the moment, Dr. Tkach have given 4 invited talks, contributed to organization of 3 scientific events and edited a book published by Nova Science Publishers. Being also an Editorial board member of Nanomater. Sci. Eng. and Coatings, he reviewed as well manuscripts for 30 scientific journals. Dr. Tkach publication profile contains 6 book chapters and 77 published articles (Web of Science h-index 23, Google Scholar h-index 25), including high impact factor Nature Physics, Adv. Funct. Mater., Chem. Mater. and Phys. Rev. Lett. Dr. Oleksandr Tkach works in the field of Materials Science & Engineering and Solid State Physics. A particular area of his scientific activity is related to oxide electroceramics.