@article{usher_forrester_mcdonnell_neuefeind_page_peterson_levin_jones_2018, title={Time-of-flight neutron total scattering with applied electric fields: Ex situ and in situ studies of ferroelectric materials}, volume={89}, ISSN={["1089-7623"]}, url={http://dx.doi.org/10.1063/1.5037609}, DOI={10.1063/1.5037609}, abstractNote={Characterizing the structural response of functional materials (e.g., piezoelectrics and ferroelectrics) to electric fields is key for the creation of structure-property relationships. Here, we present a new sample environment and data reduction routines which allow the measurement of time-of-flight neutron total scattering during the in situ or ex situ application of high voltage (<10 kV) to a sample. Instead of utilizing the entire detector space of the diffractometer, only selected regions of detector pixels with scattering at the desired angle to the sample electric field are interrogated, which allows the generation of orientation-dependent reciprocal space patterns and real-space pair distribution functions (PDFs). We demonstrate the method using the relaxor ferroelectric Na1/2Bi1/2TiO3 and observe lattice expansion parallel and contraction perpendicular to the electric field for both in situ and ex situ experiments, revealing the irreversible nature of the local scale structural changes to this composition. Additionally, changes in the distributions of nearest neighbor metal-oxygen bond lengths are observed, which have been difficult to observe in previously measured analogous orientation-dependent X-ray PDFs. Considerations related to sample positioning and background subtraction are discussed, and future research directions are suggested.}, number={9}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, publisher={AIP Publishing}, author={Usher, Tedi-Marie and Forrester, Jennifer S. and McDonnell, Marshall and Neuefeind, Joerg and Page, Katharine and Peterson, Peter F. and Levin, Igor and Jones, Jacob L.}, year={2018}, month={Sep} }
 @article{hou_aksel_fancher_usher_hoshina_takeda_tsurumi_jones_2017, title={Formation of sodium bismuth titanatebarium titanate during solid-state synthesis}, volume={100}, ISSN={["1551-2916"]}, url={http://dx.doi.org/10.1111/jace.14631}, DOI={10.1111/jace.14631}, abstractNote={AbstractPhase formation of sodium bismuth titanate (Na0.5Bi0.5TiO3 or NBT) and its solid solution with barium titanate (BaTiO3 or BT) during the calcination process is studied using in situ high‐temperature diffraction. The reactant powders were mixed and heated to 1000°C, while X‐ray diffraction patterns were recorded continuously. Phase evolutions from starting materials to final perovskite products are observed, and different transient phases are identified. The formation mechanism of NBT and NBT–xBT perovskite structures is discussed, and a reaction sequence is suggested based on the observations. The in situ study leads to a new processing approach, which is the use of nano‐TiO2, and gives insights to the particle size effect for solid‐state synthesis products. It was found that the use of nano‐TiO2 as reactant powder accelerates the synthesis process, decreases the formation of transient phases, and helps to obtain phase‐pure products using a lower thermal budget.}, number={4}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, publisher={Wiley}, author={Hou, Dong and Aksel, Elena and Fancher, Chris M. and Usher, Tedi-Marie and Hoshina, Takuya and Takeda, Hiroaki and Tsurumi, Takaaki and Jones, Jacob L.}, year={2017}, month={Apr}, pages={1330–1338} }
 @article{hou_usher_zhou_raengthon_triamnak_cann_forrester_jones_2017, title={Temperature-induced local and average structural changes in BaTiO3-xBi(Zn1/2Ti1/2)O-3 solid solutions: The origin of high temperature dielectric permittivity}, volume={122}, number={6}, journal={Journal of Applied Physics}, author={Hou, D. and Usher, T. M. and Zhou, H. H. and Raengthon, N. and Triamnak, N. and Cann, D. P. and Forrester, J. S. and Jones, J. L.}, year={2017} }
 @article{beuerlein_kumar_usher_james brown-shaklee_raengthon_reaney_cann_jones_brennecka_2016, title={Current Understanding of Structure-Processing-Property Relationships in BaTiO3-Bi(M)O-3 Dielectrics}, volume={99}, ISSN={["1551-2916"]}, url={http://dx.doi.org/10.1111/jace.14472}, DOI={10.1111/jace.14472}, abstractNote={As part of a continued push for high permittivity dielectrics suitable for use at elevated operating temperatures and/or large electric fields, modifications of BaTiO3 with Bi(M)O3, where M represents a net‐trivalent B‐site occupied by one or more species, have received a great deal of recent attention. Materials in this composition family exhibit weakly coupled relaxor behavior that is not only remarkably stable at high temperatures and under large electric fields, but is also quite similar across various identities of M. Moderate levels of Bi content (as much as 50 mol%) appear to be crucial to the stability of the dielectric response. In addition, the presence of significant Bi reduces the processing temperatures required for densification and increases the required oxygen content in processing atmospheres relative to traditional X7R‐type BaTiO3‐based dielectrics. Although detailed understanding of the structure–processing–property relationships in this class of materials is still in its infancy, this article reviews the current state of understanding of the mechanisms underlying the high and stable values of both relative permittivity and resistivity that are characteristic of BaTiO3‐Bi(M)O3 dielectrics as well as the processing challenges and opportunities associated with these materials.}, number={9}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, publisher={Wiley}, author={Beuerlein, Michaela A. and Kumar, Nitish and Usher, Tedi-Marie and James Brown-Shaklee, Harlan and Raengthon, Natthaphon and Reaney, Ian M. and Cann, David P. and Jones, Jacob L. and Brennecka, Geoff L.}, editor={Green, D. J.Editor}, year={2016}, month={Sep}, pages={2849–2870} }
 @article{usher_iamsasri_forrester_raengthon_triamnak_cann_jones_2016, title={Local and average structures of BaTiO3-Bi(Zn1/2Ti1/2)O-3}, volume={120}, number={18}, journal={Journal of Applied Physics}, author={Usher, T. M. and Iamsasri, T. and Forrester, J. S. and Raengthon, N. and Triamnak, N. and Cann, D. P. and Jones, J. L.}, year={2016} }
 @article{levin_krayzman_woicik_bridges_sterbinsky_usher_jones_torrejon_2016, title={Local structure in BaTiO3-BiScO3 dipole glasses}, volume={93}, ISSN={["2469-9969"]}, url={http://dx.doi.org/10.1103/physrevb.93.104106}, DOI={10.1103/physrevb.93.104106}, abstractNote={Local structures in cubic perovskite-type $(\mathrm{B}{\mathrm{a}}_{0.6}\mathrm{B}{\mathrm{i}}_{0.4})(\mathrm{T}{\mathrm{i}}_{0.6}\mathrm{S}{\mathrm{c}}_{0.4}){\mathrm{O}}_{3}$ solid solutions that exhibit reentrant dipole glass behavior have been studied with variable-temperature x-ray/neutron total scattering, extended x-ray absorption fine structure, and electron diffraction methods. Simultaneous fitting of these data using a reverse Monte Carlo algorithm provided instantaneous atomic configurations, which have been used to extract local displacements of the constituent species. The smaller Bi and Ti atoms exhibit probability density distributions that consist of 14 and 8 split sites, respectively. In contrast, Ba and Sc feature single-site distributions. The multisite distributions arise from large and strongly anisotropic off-center displacements of Bi and Ti. The cation displacements are correlated over a short range, with a correlation length limited by chemical disorder. The magnitudes of these displacements and their anisotropy, which are largely determined by local chemistry, change relatively insignificantly on cooling from room temperature. The structure features a nonrandom distribution of local polarization with low-dimensional polar clusters that are several unit cells in size. In situ measurements of atomic pair-distribution function under applied electric field were used to study field-induced changes in the local structure; however, no significant effects besides lattice expansion in the direction of the field could be observed up to electric-field values of $4\phantom{\rule{0.16em}{0ex}}\mathrm{kV}\phantom{\rule{0.16em}{0ex}}\mathrm{m}{\mathrm{m}}^{\ensuremath{-}1}$.}, number={10}, journal={PHYSICAL REVIEW B}, publisher={American Physical Society (APS)}, author={Levin, I. and Krayzman, V. and Woicik, J. C. and Bridges, F. and Sterbinsky, G. E. and Usher, T-M. and Jones, J. L. and Torrejon, D.}, year={2016}, month={Mar} }
 @article{usher_levin_daniels_jones_2015, title={Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics}, volume={5}, journal={Scientific Reports}, author={Usher, T. M. and Levin, I. and Daniels, J. E. and Jones, J. L.}, year={2015} }
 @article{zhao_hou_usher_iamsasri_fancher_forrester_nishida_moghaddam_jones_2015, title={Structure of 3 at.% and 9 at.% Si-doped HfO2 from combined refinement of X-ray and neutron diffraction patterns}, volume={646}, ISSN={["1873-4669"]}, url={http://dx.doi.org/10.1016/j.jallcom.2015.06.084}, DOI={10.1016/j.jallcom.2015.06.084}, abstractNote={The crystal structure of 3 at.% and 9 at.% Si-doped HfO2 powder was determined through refinements using X-ray and neutron diffraction patterns. The lattice parameters, atomic positions, dopant occupancy, and the second phase fraction were determined with high precision using a combined full pattern fitting via the Rietveld method. The results show that both 3 at.% and 9 at.% Si-doped HfO2 powder exhibit the monoclinic crystal structure with P 1 21/c 1 space group. Through the combined refinement, the crystal structure parameters, especially for the positions and occupancies of the lighter atoms, were more precisely determined compared to independent X-ray diffraction refinement. Although the ionic radius of Si4+ is smaller than Hf4+, with increasing Si occupancy, the unit cell volume slightly increases; possible mechanisms for this effect are discussed. Moreover, the refined results provide evidence of the existence of a non-equilibrium phase of HfxSi1−xO2. The second phase (SiO2) fraction is determined as 0.17 at.% for 3 at.% Si-doped HfO2 powders and 1.7 at.% for 9 at.% Si-doped HfO2 powders.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, publisher={Elsevier BV}, author={Zhao, Lili and Hou, Dong and Usher, Tedi-Marie and Iamsasri, Thanakorn and Fancher, Chris M. and Forrester, Jennifer S. and Nishida, Toshikazu and Moghaddam, Saeed and Jones, Jacob L.}, year={2015}, month={Oct}, pages={655–661} }
 @article{ursic_bencan_drazic_esteves_jones_usher_rojac_drnovsek_deluca_jouin_et al._2015, title={Unusual structural-disorder stability of mechanochemically derived-Pb(Sc0.5Nb0.5)O-3}, volume={3}, ISSN={["2050-7534"]}, url={http://dx.doi.org/10.1039/c5tc02205c}, DOI={10.1039/c5tc02205c}, abstractNote={This study demonstrates the important effect of processing on the B-site ordering in Pb(Sc0.5Nb0.5)O3ceramics.}, number={39}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, publisher={Royal Society of Chemistry (RSC)}, author={Ursic, Hana and Bencan, Andreja and Drazic, Goran and Esteves, Giovanni and Jones, Jacob L. and Usher, Tedi-Marie and Rojac, Tadej and Drnovsek, Silvo and Deluca, Marco and Jouin, Jenny and et al.}, year={2015}, pages={10309–10315} }
 @article{voas_usher_liu_li_jones_tan_cooper_beckman_2014, title={Special quasirandom structures to study the (K0.5Na0.5)NbO3 random alloy}, volume={90}, ISSN={["2469-9969"]}, url={http://dx.doi.org/10.1103/physrevb.90.024105}, DOI={10.1103/physrevb.90.024105}, abstractNote={Abstract : The local structure of K0.5Na0.5NbO3 is investigated using first-principles methods with an optimized special quasirandom structure (SQS). Through a comparison of the computed pair distribution functions with those from neutron powder diffraction data, the SQS approach demonstrates its ability to accurately capture the local structure patterns derived from the random distribution of K and Na on the perovskite A-site. Using these structures, local variations in Na-O interactions are suggested to be the driving force behind the R3c to Pm phase transition. A comparison between the SQS and a rocksalt structure shows the inability of the latter to account for the local variability present in a random solid solution. As such, the predictive nature of the SQS demonstrated here suggests that this approach may provide insight in understanding the properties of a wide range of bulk oxide alloys or solid solutions.}, number={2}, journal={PHYSICAL REVIEW B}, publisher={American Physical Society (APS)}, author={Voas, Brian K. and Usher, Tedi-Marie and Liu, Xiaoming and Li, Shen and Jones, Jacob L. and Tan, Xiaoli and Cooper, Valentino R. and Beckman, Scott P.}, year={2014}, month={Jul} }