6 / 24
allied
academies
May 20-21, 2019 | Vienna, Austria
Biomaterials and Nanomaterials &
Materials Physics and Materials Science
2
nd
International Conference on
Page 19
Journal of Materials Science and Nanotechnology | Volume 3
F
or nearly 40 years, narrow band gap semiconductors and
strong ferroelectrics are considered separate material
families. Narrow band gap semiconductors are widely
used as solar cells and optical sensors. Strong ferroelectric
materialshavethepotentialtoinducestrongpiezoelectricity.
They are core components for thermal and kinetic sensors,
actuators, transducers and energy harvesters. Some simple
and pre-mature photoferroelectrics, i.e. ferroelectrics
exhibiting photovoltaic effect (e.g. BaTiO
3
, BiFeO
3
, LiNbO
3
and (Pb, La) (Zr, TiO
3
), have been theoretically investigated
since the 1970s. However, they either have a wide band gap
or a weak ferroelectricity leading to inefficient photovoltaic
effects or insensitivity to light/electric/strain excitations,
respectively. This issue has then hindered the practical use
of these photo-ferroelectrics in potential multi-functional
devices.
In this talk, a novel multi-functional perovskite material will
be presented, which merges the two fields of narrow band
gap semiconductors and strong ferroelectrics for the first
time. The composition is a widely used lead-free ferro-/
piezoelectric composition, (K
0.5
Na
0.5
) NbO
3
(KNN), doped
by Ni2
+
and with oxygen vacancies present in the structure
(abbreviated as KNBNNO hereinafter). The KNBNNO is
able to exhibit a narrow band gap of 1.6 eV (compared
to > 4 eV) whilst maintaining the parental, KNN-level
ferroelectric, piezoelectric and pyroelectric properties.
Such multi-functional properties enable the KNBNNO to be
simultaneously used for visible-range (solar) photovoltaic
and ferro-/piezo-/pyroelectric effects. It is the first
materials of its kind discovered in history.
Together with its microstructure and working principles,
demonstrations will also be shown in this talk for
practical applications of the KNBNNO. These include a
single-component, multi-source energy harvester-sensor
integration system based on only one material, and an
opto-ferroelectric component with interactions between
light and domain walls for e.g. light-re-writable data
storage distinguishing wavelengths.
Speaker Biography
Yang Bai is a tenure track assistant professor for small-power self-
sufficient sensor system in microelectronics research unit, University
of Oulu, Finland. He obtained his bachelor’s degree in 2011 at Tianjin
University, China, and PhD degree in 2015 at University of Birmingham,
United Kingdom. In 2016, he was granted a Marie Sklodowska-Curie
individual fellowship under European Union’s Horizon 2020 research
and innovation program. He is also an elected committee member of
the IOP (Institute of Physics) energy group, UK. His research interests
include multi-functional perovskites, photo-ferroelectrics, ferroelectric
and piezoelectric materials and energy harvesting technology.
e:
yang.bai@oulu.fiYang Bai
University of Oulu, Finland
A narrow band gap, strong ferroelectric perovskite oxide opening up
next-generation opto-ferroelectric and energy harvesting devices
Notes: