Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3. The defects were identified as Fe4+ cations and bismuth vacancies, revealing p-type hopping conduction at domain walls caused by the presence of electron holes associated with Fe4. In agreement with the p-type behaviour, we further show that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. This work has possible implications for engineering local conductivity in ferroelectrics and for devices based on domain walls.
COBISS.SI-ID: 29936679
On the last page of every issue of the prominent journal Nature Chemistry a different chemical element is presented under the section captioned “In Your Element”. Invited article "The world of krypton revisited", which describes the element krypton and was published in the July 2016 issue, was written by dr. Matic Lozinšek and prof. dr. Gary J. Schrobilgen. Krypton is the lightest member of the noble gas group which forms compounds that are isolable in macroscopic amounts. All known compounds of krypton have been derived from krypton difluoride which is thermodynamically unstable and a very potent oxidative fluorinator. Krypton chemistry research is therefore experimentally very challenging and only a handful of laboratories around the world possess the necessary know-how.
COBISS.SI-ID: 29676327
The M2AgF4 series (M = K, K3/4Rb1/4, K1/2Rb1/2, K1/4Rb3/4, Rb, Cs) have been studying using temperature-resolved X-ray diffraction and heat capacity measurements, magnetometry, and HFEPR spectroscopy. Results suggest that all double perovskite fluoroargentates(II) phases, including HT-K2AgF4, adopt structures consisting of an antiferrodistortive arrangement of the elongated [AgF6]4− octahedra, in agreement with recent theoretical calculations. The temperature-resolved phase diagram of the M = K/Rb phases has been investigated in the 2−350 K temperature window, adding to the existing data for the M = Na to Cs members. This phase diagram shows a systematic trend in the temperatures of the phase transitions involving two orthorhombic phases and one tetragonal phase, which most probably arises from various tilting distortions within the doubleperovskite structure. The phase diagram is further complicated by the thermodynamic preference for the 1D postperovskite structure for M = Na, K.
COBISS.SI-ID: 29923879
The structural chemistry of inorganic fluorides is dominated by the simple electrostatic and geometrical principles for which the coordination number of six with an octahedral coordination is favoured for nearly all transition metals. Instead of being isolated, the resulting octahedra can share their F ligands forming oligomeric or polymeric species. The crystal structure determination of [XeF5]5[Ti10F45] reveals the largest known oligomeric fluorido-metallate [Ti10F45]5– anion built from ten TiF6 octahedra, sharing vertices, in the shape of a double-star. The contribution has been selected for the inside front cover of September issue (2016) of New Journal of Chemistry.
COBISS.SI-ID: 29704743
Reactions of N-heterocyclic carbene 1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene (LDipp) with Et3N.3HF reagent readily affords [(LDipp)H]+ [(HF)nF] (n = 0–2) salts with 1:1, 1:2, 1:3 ratios of HF. Product [(LDipp)H]+[F]− shows a free fluoride reagent characteristics and can be selectively synthesised from reactions of (LDipp) with stoichiometric quantities of Et3N.3HF or KHF2 without any halide or water impurities on a gram scale. Reactions of Et3N.3HF or KHF2 with (LDipp) were performed in glassware with no sign of glass etching by the reagents.
COBISS.SI-ID: 30189863