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1. Down regulation of APETALA 3 homolog resulted in defect of floral structure critical to explosive pollen release in Cornus canadensis: The role of APETALA3 homolog in Cornus

   https://doi.org/10.1111/jse.12272  

   Liu, Xiang ; Li, Lu ; Jenny Xiang, Qiu-Yun ( November 2017 , Journal of Systematics and Evolution)
2. Synthesis of Defect Perovskites (He 2–x □ x )(CaZr)F 6 by Inserting Helium into the Negative Thermal Expansion Material CaZrF 6

   https://doi.org/10.1021/jacs.7b07860  

   Hester, Brett R. ; dos Santos, António M. ; Molaison, Jamie J. ; Hancock, Justin C. ; Wilkinson, Angus P. ( September 2017 , Journal of the American Chemical Society)
3. Perovskite Na-ion conductors developed from analogous Li 3x La 2/3−x TiO 3 (LLTO): chemo-mechanical and defect engineering

   https://doi.org/10.1039/d1ta04252a  

   Lin, Yu-Ying ; Gustafson, William J. ; Murray, Shannon E. ; Shoemaker, Daniel P. ; Ertekin, Elif ; Krogstad, Jessica A. ; Perry, Nicola H. ( September 2021 , Journal of Materials Chemistry A)

   Na-ion conducting solid electrolytes can enable both the enhanced safety profile of all-solid-state-batteries and the transition to an earth-abundant charge-carrier for large-scale stationary storage. In this work, we developed new perovskite-structured Na-ion conductors from the analogous fast Li-ion conducting Li 3 x La 2/3− x TiO 3 (LLTO), testing strategies of chemo-mechanical and defect engineering. Na x La 2/3−1/3 x ZrO 3 (NLZ) and Na x La 1/3−1/3 x Ba 0.5 ZrO 3 (NLBZ) were prepared using a modified Pechini method with varying initial stoichiometries and sintering temperatures. With the substitution of larger framework cations Zr 4+ and Ba 2+ on B- and A-sites respectively, NLZ and NLBZ both had larger lattice parameters compared to LLTO, in order to accommodate and potentially enhance the transport of larger Na ions. Additionally, we sought to introduce Na vacancies through (a) sub-stoichiometric Na : La ratios, (b) Na loss during sintering, and (c) donor doping with Nb. AC impedance spectroscopy and DC polarization experiments were performed on both Na 0.5 La 0.5 ZrO 3 and Na 0.25 La 0.25 Ba 0.5 ZrO 3 in controlled gas environments (variable oxygen partial pressure, humidity) at elevated temperatures to quantify the contributions of various possible charge carriers (sodium ions, holes, electrons, oxygen ions, protons). Our results showed that the lattice-enlarged NLZ and NLBZ exhibited ∼19× (conventional sintering)/49× (spark plasma sintering) and ∼7× higher Na-ion conductivities, respectively, compared to unexpanded Na 0.42 La 0.525 TiO 3 . Moreover, the Na-ion conductivity of Na 0.5 La 0.5 ZrO 3 is comparable with that of NaNbO 3 , despite having half the carrier concentration. Additionally, more than 96% of the total conductivity in dry conditions was contributed by sodium ions for both compositions, with negligible electronic conductivity and little oxygen ion conductivity. We also identified factors that limited Na-ion transport: NLZ and NLBZ were both challenging to densify using conventional sintering without the loss of Na because of its volatility. With spark plasma sintering, higher density can be achieved. In addition, the NLZ perovskite phase appeared unable to accommodate significant Na deficiency, whereas NLBZ allowed some. Density functional theory calculations supported a thermodynamic limitation to creation of Na-deficient NLZ in favor of a pyrochlore-type phase. Humid environments generated different behavior: in Na 0.25 La 0.25 Ba 0.5 ZrO 3 , incorporated protons raised total conductivity, whereas in Na 0.5 La 0.5 ZrO 3 , they lowered total conductivity. Ultimately, this systematic approach revealed both effective approaches and limitations to achieving super-ionic Na-ion conductivity, which may eventually be overcome through alternative processing routes. 

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4. Defect accommodation in off-stoichiometric (SrTiO 3 ) n SrO Ruddlesden–Popper superlattices studied with positron annihilation spectroscopy

   https://doi.org/10.1063/5.0011136  

   Dawley, Natalie M. ; Goodge, Berit H. ; Egger, Werner ; Barone, Matthew R. ; Kourkoutis, Lena F. ; Keeble, David J. ; Schlom, Darrell G. ( August 2020 , Applied Physics Letters)

   null (Ed.)
5. Defect generation in TiO 2 nanotube anodes via heat treatment in various atmospheres for lithium-ion batteries

   https://doi.org/10.1039/c8cp04368j  

   Savva, Andreas I. ; Smith, Kassiopeia A. ; Lawson, Matthew ; Croft, Sterling R. ; Weltner, Ariel E. ; Jones, Chris D. ; Bull, Hailey ; Simmonds, Paul J. ; Li, Lan ; Xiong, Hui ( January 2018 , Physical Chemistry Chemical Physics)

   In this paper, ordered TiO 2 nanotubes were grown on a Ti substrate via electrochemical anodization and subsequently annealed at 450 °C for 4 h under various atmospheres to create different point defects. Oxygen-deficient environments such as Ar and N 2 were used to develop oxygen vacancies, while a water vapor (WV) atmosphere was used to generate titanium vacancies. Computational models by density functional theory predicted that the presence of oxygen vacancies would cause electronic conductivity to increase, while the presence of Ti vacancies could lead to decreased conductivity. The predictions were confirmed by two-point electrical conductivity measurements and Mott–Schottky analysis. Raman spectroscopy was also conducted to confirm the presence of defects. The annealed samples were then evaluated as anodes in lithium-ion batteries. The oxygen-deficient samples had an improvement in capacity by 10% and 25% for Ar- and N 2 -treated samples, respectively, while the WV-treated sample displayed a capacity increase of 24% compared to the stoichiometric control sample (annealed in O 2 ). Electrochemical impedance spectroscopy studies revealed that the WV-treated sample's increased capacity was a consequence of its higher Li diffusivity. The results suggest that balanced electrical and ionic conductivity in nanostructured metal oxide anodes can be tuned through defect generation using heat treatments in various atmospheres for improved electrochemical properties. 

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