More Like this

1. Formation of Homoleptic Zirconium and Hafnium Dithiocarbamates via Insertion of CS ₂ : Breaking Bonds and Taking Names

   https://doi.org/10.1021/acs.organomet.4c00152  

   Uible, Madeleine C; Prokop, Brandon S; Hayes, Daniel C; Chaudhuri, Subhajyoti; Vincent, Kiruba Catherine; Pradhan, Apurva A; Rounds, Ace; Turnley, Jonathan W; Agarwal, Shubhanshu; Swope, Ryan N; et al (June 2024, Organometallics)

   Synthesis of homoleptic zirconium and hafnium dithiocarbamate via carbon disulfide insertion into zirconium and hafnium amides were investigated for their utility as soluble molecular precursors for chalcogenide perovskites and binary metal sulfides. Treating M(NEtR)4 (M= Zr, Hf and R= Me, Et) with CS2 resulted in quantitative yields of homoleptic Group IV dithiocarbamates. Zr(2-S2CNMeEt) (1), Zr(2-S2CNEt2)4 (2), and Hf(2-S2CNEt2)4 (4), a rare example of a crystal of a homoleptic hafnium CS2 inserted amide species, were characterized. A computational analysis confirmed assignments for IR spectroscopy. To exemplify the utility of the Group IV dithiocarbamates, a solution-phase nanoparticle synthesis was performed to obtain ZrS3 via the thermal decomposition of Zr(S2CNMeEt)4. 

   more » « less
2. Charge Transport in the A ₆ B ₂ O ₁₇ (A = Zr, Hf; B = Nb, Ta) Superstructure Series

   https://doi.org/10.1149/1945-7111/ad2d90  

   Miruszewski, Tadeusz; Mielewczyk-Gryń, Aleksandra; Jaworski, Daniel; Rosenberg, William Foute; McCormack, Scott J; Gazda, Maria (March 2024, Journal of The Electrochemical Society)

   The electrical properties of the entropy stabilized oxides: Zr₆Nb₂O₁₇, Zr₆Ta₂O₁₇, Hf₆Nb₂O₁₇and Hf₆Ta₂O₁₇were characterized. The results and the electrical properties of the products (i.e. ZrO₂, HfO₂, Nb₂O₅and Ta₂O₅) led us to hypothesize the A₆B₂O₁₇family is a series of mixed ionic-electronic conductors. Conductivity measurements in varying oxygen partial pressure were performed on A₆Nb₂O₁₇and A₆Ta₂O_17.The results indicate that electrons are involved in conduction in A₆Nb₂O₁₇while holes play a role in conduction of A₆Ta₂O₁₇. Between 900 °C–950 °C, the charge transport in the A₆B₂O₁₇system increases in Ar atmosphere. A combination of DTA/DSC and in situ high temperature X-ray diffraction was performed to identify a potential mechanism for this increase. In-situ high temperature X-ray diffraction in Ar does not show any phase transformation. Based on this, it is hypothesized that a change in the oxygen sub-lattice is the cause for the shift in high temperature conduction above 900 °C–950 °C. This could be:(i)Nb(Ta)⁴⁺- oxygen vacancy associate formation/dissociation,(ii)formation of oxygen/oxygen vacancy complexes(iii)ordering/disordering of oxygen vacancies and/or(iv)oxygen-based superstructure commensurate or incommensurate transitions. In-situ high temperature neutron diffraction up to 1050 °C is required to help elucidate the origins of this large increase in conductivity. 

   more » « less
3. Exceptional TcO ₄ ⁻ sorption capacity and highly efficient ReO ₄ ⁻ luminescence sensing by Zr ⁴⁺ MOFs

   https://doi.org/10.1039/c8ta07901c  

   Rapti, Sofia; Diamantis, Stavros A.; Dafnomili, Argyro; Pournara, Anastasia; Skliri, Euaggelia; Armatas, Gerasimos S.; Tsipis, Athanassios C.; Spanopoulos, Ioannis; Malliakas, Christos D.; Kanatzidis, Mercouri G.; et al (October 2018, Journal of Materials Chemistry A)

   The sorption properties of [Zr 6 O 4 (OH) 4 (NH 3 + -BDC) 6 ]Cl 6 · x H 2 O ( MOR-1 ) and H 16 [Zr 6 O 16 (H 2 PATP) 4 ]Cl 8 · x H 2 O ( MOR-2 ) towards ReO 4 − and TcO 4 − were studied in detail. Both MOR-1 and MOR-2 are very effective sorbents for ReO 4 − and TcO 4 − anions, with MOR-2 showing the highest sorption capacity (up to 4.1 ± 0.4 mmol g −1 ) among the known metal organic materials. Importantly, the exceptional sorption capacity of MOR-2 is retained even under conditions simulating acidic nuclear waste. In addition, MOR-1 and MOR-2 exhibit selective luminescence ReO 4 − sensing properties, demonstrated for the first time for MOF materials. 

   more » « less
4. Room temperature synthesis of lead-free FASnI ₃ perovskite nanocrystals with improved stability by SnF ₂ additive

   https://doi.org/10.1063/5.0125100  

   Chen, Zeying; Dhakal, Tara P. (March 2023, Applied Physics Reviews)

   Tin halide perovskites are among the candidates for replacing lead-based ones for less toxicity and comparable optical properties. However, stability remains a challenge due to the easier oxidation of Sn 2+ than Pb 2+ . Here, for the first time, we applied the ligand-assisted reprecipitation method to synthesize CH(NH 2 ) 2 SnI 3 (FASnI 3 ) orthorhombic perovskite nanocrystals with an average diameter of 7.7 nm and a photoluminescence emission at 825 [Formula: see text] 2 nm (1.5 eV). The influence of synthesis parameters, including precursor solvent, precipitation media, temperature, and time on optical properties of nanocrystals, was studied. By incorporating SnF 2 , the stability of the nanocrystals was improved, and the oxidation from FASnI 3 to FA 2 SnI 6 was significantly delayed, which was quantitively demonstrated and confirmed by observing the characteristic diffraction peaks of the perovskite phase using x-ray diffraction at various exposure time to air. The addition of SnF 2 is optimized to be 6%. The FASnI 3 nanocrystals stayed stable for at least 265 days under N 2 storage at room temperature and relative humidity of 20%. 

   more » « less
5. Resolving Mechanical Properties and Morphology Evolution of Free‐Standing Ferroelectric Hf _0.5 Zr _0.5 O ₂

   https://doi.org/10.1002/adem.202101221  

   Tharpe, Troy; Zheng, Xu-Qian; Feng, Philip_X-L; Tabrizian, Roozbeh (October 2021, Advanced Engineering Materials)

   Advances in creating polar structures in atomic‐layered hafnia‐zirconia (Hf_xZr_1−xO₂) films not only augurs extensive growth in studying ferroelectric nanoelectronics and neuromorphic devices, but also spurs opportunities for exploring novel integrated nanoelectromechanical systems (NEMS). Design and implementation of Hf_xZr_1−xO₂NEMS transducers necessitates accurate knowledge of elastic and electromechanical properties. Up to now, all experimental approaches for extraction of morphological content, elastic, and electromechanical properties of Hf_xZr_1−xO₂are based on solidly mounted structures, highly stressed films, and electroded architectures. Unlike Hf_xZr_1−xO₂layers embedded in electronics, NEMS transducers require free‐standing structures with highly contrasted mechanical boundaries and stress profiles. Here, a nanoresonator‐based approach for simultaneous extraction of Young's modulus and residual stress in free‐standing ferroelectric Hf_0.5Zr_0.5O₂films is presented. High quality factor resonance modes of nanomechanical resonators created in predominantly orthorhombic Hf_0.5Zr_0.5O₂films are measured using nondestructive optical transduction. Further, the evolution of morphology during creation of free‐standing Hf_0.5Zr_0.5O₂structures is closely mapped using X‐ray diffraction measurements, clearly showing transformation of ferroelectric orthorhombic to nonpolar monoclinic phase upon stress relaxation. The extracted Young's modulus of 320.0 ± 29.4 GPa and residual stress ofσ = 577.4 ± 24.1 MPa show the closest match with theoretical calculations for orthorhombic Hf_0.5Zr_0.5O₂. 

   more » « less