@article{gabilondo_newell_chestnut_weng_jones_maggard_2022, title={Circumventing thermodynamics to synthesize highly metastable perovskites: nano eggshells of SnHfO3}, volume={11}, ISSN={["2516-0230"]}, DOI={10.1039/d2na00603k}, abstractNote={Sn(II)-based perovskite oxides, being the subject of longstanding theoretical interest for the past two decades, have been synthesized for the first time in the form of nano eggshell particles. All...}, journal={NANOSCALE ADVANCES}, author={Gabilondo, Eric A. and Newell, Ryan J. and Chestnut, Jessica and Weng, James and Jones, Jacob L. and Maggard, Paul A.}, year={2022}, month={Nov} }
 @article{gabilondo_o'donnell_newell_broughton_mateus_jones_maggard_2022, title={Renaissance of Topotactic Ion-Exchange for Functional Solids with Close Packed Structures}, volume={4}, ISSN={["1521-3765"]}, DOI={10.1002/chem.202200479}, abstractNote={Recently, many new, complex, functional oxides have been discovered with the surprising use of topotactic ion-exchange reactions on close-packed structures, such as found for wurtzite, rutile, perovskite, and other structure types. Despite a lack of apparent cation-diffusion pathways in these structure types, synthetic low-temperature transformations are possible with the interdiffusion and exchange of functional cations possessing ns2 stereoactive lone pairs (e. g., Sn(II)) or unpaired ndx electrons (e. g., Co(II)), targeting new and favorable modulations of their electronic, magnetic, or catalytic properties. This enables a synergistic blending of new functionality to an underlying three-dimensional connectivity, i. e., [-M−O-M-O-]n, that is maintained during the transformation. In many cases, this tactic represents the only known pathway to prepare thermodynamically unstable solids that otherwise would commonly decompose by phase segregation, such as that recently applied to the discovery of many new small bandgap semiconductors.}, journal={CHEMISTRY-A EUROPEAN JOURNAL}, author={Gabilondo, Eric and O'Donnell, Shaun and Newell, Ryan and Broughton, Rachel and Mateus, Marcelo and Jones, Jacob L. and Maggard, Paul A.}, year={2022}, month={Apr} }
 @article{gabilondo_o'donnell_broughton_jones_maggard_2021, title={Synthesis and stability of Sn(II)-containing perovskites: (Ba,Sn-II)(HfO3)-O-IV versus (Ba,Sn-II)(SnO3)-O-IV}, volume={302}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2021.122419}, abstractNote={While Sn(II)-containing perovskite oxides have long drawn attention as Pb(II) substitutes in technologically-relevant dielectric materials, they are also highly thermodynamically unstable and potentially impossible to prepare. Investigations into the new flux-mediated syntheses of metastable Sn(II)-containing hafnate and stannate perovskites were aimed at understanding the key factors related to their synthesizability. The BaHfO 3 perovskite was reacted with SnClF from 250 to 350 ​°C for 12–72 ​h, yielding an unprecedented Sn(II) concentration on the A-site of up to ~70 ​mol%, i.e., (Ba 0.3 Sn 0.7 )HfO 3 in high purity. Elemental mapping using EDS shows the Sn(II) cations diffuse gradually throughout the crystallites, with two reaction cycles needed to give a nearly homogeneous distribution. In contrast, similar reactions with BaSnO 3 and as little as 10 ​mol% Sn(II) result in decomposition to SnO, SnO 2 , and BaSnO 3 . The (Ba 1- x Sn x )HfO 3 compositions exhibit a primary cubic perovskite structure ( Pm 3 ¯ m ; for x ​= ​1/3, 1/2 and 2/3) by powder X-ray diffraction (XRD) methods, with the Sn(II) cations substituted on the A-site. Total energy calculations show the thermodynamic instability versus the ground state (i.e., metastability) for (Ba 1- x Sn x )HfO 3 increases with Sn(II) substitution, reaching a maximum of ~446 ​meV atom −1 at ~70 ​mol% Sn(II). The decomposition pathway of (Ba 1/3 Sn 2/3 )HfO 3 was probed by ex situ XRD as well as in situ electron microscopy methods. An onset of thermally-induced decomposition begins at ~350–400 ​°C to give the more stable oxides which are found to segregate out in surface layers. These results help to elucidate the factors underpinning the synthesizability of highly metastable Sn(II)-containing perovskites, which increases with their cohesive energy and with the absence of lower-energy polymorphs or other ground states that can be reached without significant ion diffusion. • Novel Sn(II)-containing oxide perovskites were prepared using a low temperature flux-mediated synthetic approach. • Relationships between the synthesizability and metastability of perovskite oxides were elucidated. • Structural factors increasing kinetic stabilization include larger cohesive energy and the inhibition of ion diffusion. • Ex situ and in situ decomposition pathways were probed using powder XRD and electron microscopy techniques.}, journal={JOURNAL OF SOLID STATE CHEMISTRY}, author={Gabilondo, Eric A. and O'Donnell, Shaun and Broughton, Rachel and Jones, Jacob L. and Maggard, Paul A.}, year={2021}, month={Oct} }