HPSynC 2017 Research Highlights

2018 |2017 | 2016

High-Pressure Band-Gap Engineering in Lead-Free Cs2AgBiBr6 Double Perovskite
High-Pressure Band-Gap Engineering in Lead-Free Cs2AgBiBr6 Double Perovskite
Researchers have been considering Cs2AgBiBr6 as a good candidate material for photovoltaic applications because of its unique optical and electronic properties, structure stability and lead-toxic free feature. However, the relatively large band gap of 2.2eV has been a big hurdle for the development of Cs2AgBiBr6 based optoelectronic devices. Recently, for the first time, a group of scientists successfully narrowed the band gap of this material from 2.2eV to 1.7eV, a 22.3% reduction, by applying high pressure. Moreover, the band gap reduction partially sustained after the pressure was released to ambient condition. This study demonstrates that high pressure can play an important role in engineering the band gap of functional semiconductors.More...

Oxygen-Rich Lithium Oxide Phases Formed at High Pressure for Potential Lithium–Air Battery Electrode
Oxygen-Rich Lithium Oxide Phases Formed at High Pressure for Potential Lithium–Air Battery Electrode
By using high pressure synchrotron technics, a group of scientists from HPSTAR, Geo Lab at Carnegie Institution of Science and Argonne National Laboratory investigated the stability of lithium oxides and discovered three stable high-pressure phases of oxygen-rich lithium oxides under high pressure and temperature: LiO2 (P4/mbm), Li2O3 (Im-3m) and LiO4 (lbam). The researchers further explored the cause of these new stable high-pressure phases and their corresponding structures. This study rolled out a new platform for battery designs and applications under extreme conditions.More...

Synthesis of quenchable amorphous diamond
Synthesis of quenchable amorphous diamond
Although it has been long expected that purely sp3-bonded tetrahedral amorphous carbon materials have broad prospects in industrial applications due to their unique properties, such as ultra-high hardness, extremely low friction and outstanding wear resistance, scientists had never observed or achieved complete sp3 bonding amorphous carbon under ambient conditions. Recently, for the first time, a collaboration team has successfully turned mostly sp2 bonded glassy carbon to purely sp3 bonded "amorphous diamond" by using HPHT and DAC technics. The sp2-to-sp3 transformation is irreversible when temperature and pressure fall back to ambient conditions.More...

Abnormal Pressure-Induced Photoluminescence Enhancement and Phase Decomposition in Pyrochlore La2Sn2O7
Abnormal Pressure-Induced Photoluminescence Enhancement and Phase Decomposition in Pyrochlore La2Sn2O7
Recently, a collaborative study was done on La2Sn2O7. The research results indicated that La2Sn2O7 could be a good candidate material for new types of optical pressure sensors that can be used under extreme conditions such as chemical reactors. The predication was based on the discovery of 1)a peak with flat maximum PL on the top and steep edges on both sides within a well-defined pressure window between 6.6 and 16.6 GPa and 2)the observations of abnormal near-infrared photoluminescence (PL) from La2Sn2O7 sample at ambient pressure and visible narrow-band PL when above-2-GPa- pressure was induced to the sample. The study further explored the causes of these interesting phenomena. More...

Ferroelectrics: Enhanced Ferroelectric and Visible-Light Photoelectric Properties in Multiferroic KBiFe2O5 via Pressure-Induced Phase Transition
Ferroelectrics: Enhanced Ferroelectric and Visible-Light Photoelectric Properties in Multiferroic KBiFe2O5 via Pressure-Induced Phase Transition
New study from a team of HPSTAR scientists, led by Drs. Ganghua Zhang and Wenge Yang, find that pressure can simultaneously enhance ferroelectric and photoelectric properties of multiferroic KBiFe2O5. These findings may open a new avenue to discovering and designing optimal ferroelectric compounds for solar energy applications. The work was highlighted on the Advanced Electronic Materials cover inside. More...

Stability of Ar(H2)2 to 358 GPa
Stability of Ar(H2)2 to 358 GPa Hydrogen-rich materials have been predicted to be promoters for the metallization of hydrogen. A group of scientists led by HPSTAR director, Dr. Ho-kwang Mao has studied Ar(H2)2, a hydrogen-rich material formed by Argon (Ar) and Hydrogen (H2), to 358 gigapascals— almost the pressure in the inner core of the Earth, by combining experimental and theoretical methods. Contrary to the previous thought, it was observed that Ar damps the intermolecular interactions between H2 molecules, an effect as ‘negative’ chemical pressure which postpones metallization. The results were published in Proceeding of the National Academic of Sciences, USA. More...

Dehydrogenation of goethite in Earth’s deep lower mantle
The hydrogen cycling in the deep Earth. Image courtesy Qingyang Hu.
In Earth interior, water (H2O) plays an important role in rock physics but geoscientists rarely treat water in its decomposable forms, like hydrogen plus oxygen. However, new work from a team led by HPSTAR director, Dave Mao, has identified the hydrogen can escape from the water under lower mantle conditions. Their results were published in Proceeding of the National Academic Science, U.S.A.More...