Oliver Alderman
<oalderman@matsdev.com>

Oliver Alderman currently works as Research Scientist at Materials Development Inc. and is a Visiting Scientist at Argonne National Laboratory.  He obtained an MPhys degree in Physics in 2009, and a PhD in 2013, both at the University of Warwick.  His PhD studies included the use of x-ray and neutron diffraction and nuclear magnetic resonance spectroscopy to study the structure of oxide glasses and related materials.  Current topics of research include the study of highly refractory melts and the temperature dependent structure of liquids during supercooling, glass formation, or redox, primarily through the use of the containerless aerodynamic levitation and laser heating approach, combined with scattering and spectroscopic techniques and computational modelling.

 

Liquid and glassy barium titanates
O.L.G. Alderman1,2,* C.J. Benmore2, J. Neuefiend3, S. Heald2, C. Weiss1, S. Sendelbach1, A. Tamalonis1, L.B. Skinner2,4, J.K.R. Weber1,2
1
MaterialsDevelopment Inc., Arlington Heights, IL60004, USA

2X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne IL 60439, USA
3Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA 
4Mineral Physics Institute, Stony Brook University, Stone Brook, New York, NY 11794-2100, USA

Molten barium titanates are important systems for crystal growth of ferroelectrics, as well as models for titanate rich metallurgical slags, high-pressure molten silicate analogues, and can even be vitrified at compositions close to the BaTi2O5 eutectic to yield novel optical materials.

In this talk I will present a broad range of experimental data pertaining to the atomic scale structure of liquid and glassy barium titanates, including neutron diffraction with Ti isotope substitution, high-energy x-ray diffraction and Ti K-edge x-ray absorption spectroscopy. All in-situ measurements were made using containerless aerodynamic levitation combined with CO2 laser heating.  Results clearly demonstrate that Ti4+-O coordination in the melts ranges between 4 and 5, i.e. lower than 6, as found in most of the isocompositional crystal structures.  Furthermore, significant increases in Ti-O coordination were found on cooling through the glass transition.

To improve our understanding of liquid and amorphous BaO-TiO2, molecular dynamics models were derived which give reasonable reproductions of existing density and scattering data.  These models were then used to interpolate and extrapolate in temperature-composition space in order to unpick the structure-property relationships.

References:
Alderman, O.L.G., et al., Phys. Rev. B, 2014. 90(9): 094204
Alderman, O.L.G., et al., J. Phys. Chem. C, 2016. 120(47): 26974