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Dense fully stabilized cubic zirconia, sintered by the spark plasma sintering (SPS) method, was characterized through hardness, fracture toughness, and electrical impedance measurements. The effect of sintering temperature on hardness and fracture toughness was evaluated. Samples sintered at 1200°C for 5 min, which had crystallite size of <100 nm, exhibited the highest hardness. Impedance measurements showed an increase in bulk contribution relative to grain boundaries as sintering temperature is increased. Calculation of the activation energy for conduction gave a value, 1.13 eV, in agreement with previously published results.

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In this paper we report an extensive neutron diffraction investigation at high temperature on the BaCe 0.80 Y 0.20 O 2.9 proton conducting material. Our results precisely define the structural evolution of the compound as a function of temperature which is from a monoclinic (room temperature) to a cubic (800°C) structure. Neutron data have been correlated to calorimetric measurements (TGA and DSC) and conductivity properties of the material.

Structure, cation distribution, Mn oxidation states, and conductivity behavior of the Mn-substituted (up to 30% of Ti ions) Li 4 Ti 5 O 12 have been investigated by the combined use of X-ray powder diffraction, electron paramagnetic resonance (EPR), 7 Li MAS NMR, and impedance spectroscopy techniques. The spinel structure of the lithium titanate is preserved and the lattice parameter decreases with increasing the Mn content. Mn 2+ ions progressively occupy the tetrahedral site up to an approximately constant value reached for 10% Mn-substituted samples. Mn 3+ ions occupy both octahedral and tetrahedral sites, with a constant value on the tetrahedral one, independent of the total Mn amount; Mn 4+ ions are not detected. The Mn 2+ paramagnetic ions give rise to a through-space interaction with Li + ions of both cationic sites, as evaluated by the area, proportional to the Mn 2+ ions content, of a peak at ∼8 ppm observed in the 7 Li NMR spectra for the substituted samples. The obtained cation distribution and the Mn valence states satisfactorily explain the decrease of conductivity observed in the Mn-doped samples with respect to the pure Li 4 Ti 5 O 12 .