Cubic, fluorite-structured solid solutions ZrYO (YSZ; x = 0.4-0.7) were prepared by sol-gel synthesis. Impedance measurements on pellets of 85% approximate density sintered at 1300 °C for 24 h showed strong evidence of oxide ion conduction with an inclined Warburg spike at low frequencies and capacitance values of ∼10 F cm at 40 Hz. Arrhenius plots of total pellet conductivities were linear with activation energies of 1.4-1.56 eV. The conductivity decreased with x and was 2-4 orders of magnitude lower than that with optimized YSZ, x = 0.08. When the atmosphere was changed from N to O during impedance measurements, two reversible effects were seen: the Warburg spike contracted greatly, and the sample resistance decreased. These effects were more noticeable at higher x and are attributed to the introduction of p-type electronic conduction, in parallel with the preexisting oxide ion conduction. A similar reversible result was observed upon application of a direct-current (dc) bias during impedance measurements. When either pO is increased or a dc bias is applied, hole creation is believed to arise by the ionization of underbonded oxide ions situated near the Y dopant ions. The ionized electrons are trapped at surface oxygen species, and the holes that are left on oxygen are responsible for p-type conduction. The electrolytic domain of x = 0.4-0.7 extends up to approximately 10 atm of O before p-type conduction is observed. The upper pO limit of the electrolytic domain of x = 0.08 is not known but is likely to be close to or slightly above 1 atm of O.

The unitary group approach (UGA) to the many-fermion problem is based on the Gel'fand-Tsetlin (G-T) representation theory of the unitary or general linear groups. It exploits the group chain U(n) ⊃ U(n − 1) ⊃ • • • ⊃ U(2) ⊃ U(1) and the associated G-T triangular tableau labeling basis vectors of the relevant irreducible representations (irreps). The general G-T formalism can be drastically simplified in the many-electron case enabling an efficient exploitation in either configuration interaction (CI) or coupled cluster (CC) approaches to the molecular electronic structure. However, while the reliance on the G-T chain provides an excellent general formalism from the mathematical point of view, it has no specific physical significance and dictates a fixed Yamanouchi-Kotani coupling scheme, which in turn leads to a rather arbitrary linear combination of distinct components of the same multiplet with a given orbital occupancy. While this is of a minor importance in molecular orbital (MO) based CI approaches, it is very inconvenient when relying on the valence bond (VB) scheme, since the G-T states do not correspond to canonical Rumer structures. While this shortcoming can be avoided by relying on the Clifford algebra UGA (CAUGA) formalism, which enables an exploitation of a more or less arbitrary coupling scheme, it is worthwhile to point out the suitability of the so-called Verma basis sets for the VB-type approaches. Keywords Valence bond (VB) method • unitary group approach (UGA) • Verma bases • covalent and ionic VB structures • π-electron model • canonical vs non-canonical VB structures

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Oxide ion conducting yttria-stabilised zirconia ceramics show the onset of electronic conduction under a small bias voltage. Compositions with a high yttria content undergo a transition from p-type to n-type behavior at voltages in the range 2.4 to 10 V, which also depends on oxygen partial pressure. Surface reactions have a direct influence on bulk electronic conductivities, with possible implications for voltage-induced flash phenomena and resistive switching.

Nanoparticles of the ceramic pigment with composition Ti 0.97 Cr 0.015 Sb 0.015 O 2 were prepared by microemulsion-mediated solvothermal method at 180 ºC. Anatase or rutile single phase was obtained depending on the synthesis conditions. Scanning electron microscope analysis showed the formation of nanospheres with particle size around 600 nm. The anatase to rutile transformation temperature was determined by Raman spectroscopy. The evolution of the colour was studied, and it was related with the polymorphic transition. Yellow nanopigments were obtained at low temperature and huge orange colour was observed at high temperature. Nanopigments prepared at 180 ºC were tested with an industrial frit. Similar chromatic coordinates of an industrial orange ceramic pigment obtained at high temperatures were observed. -potential values of the nanoparticles were  -57 mV. The size, shape, colour and electrostatic stability of these nanoparticles make them potential candidates to be applied in glazes or inkjet printers as orange ceramic pigments.