Farm Land Ownership as a Source of Retirement Income

Land Economics/Use,

ZrO2 phase structure in coating films and powders obtained by sol-gel process

Zirconia coating film and powder obtained by the sol-gel route using zirconium n-propoxide as starting material and acid catalyst were investigated by the Perturbed Angular Correlations method, X-Ray Diffraction and Differential Scanning Calorimetry and Differential Thermal Analyses. The hyperfine interaction, measured after annealing the samples at increasing temperatures up to 1100°C, allowed to distinguish five different zirconium neighborhoods. Two of them describe rather disordered material which, on heating, crystallizes to the tetragonal phase and end finally in monoclinic zirconia. As compared with the powder, the film exhibits a minor fraction of an unidentified ordered form and a higher and more stable fraction of tetragonal phase. In addition, the tetragonal to monoclinic conversion takes place at higher temperatures and with a larger activation energy.Facultad de Ciencias Exacta

ZrO<SUB>2</SUB> and ZrO<SUB>2</SUB>-Y<SUB>2</SUB>O<SUB>3</SUB> Phase Structure in Films and Powders

Zirconia and zirconia-yttria coating films and powders obtained by the sol-gel route using a zirconium alkoxide as starting material and acid and neutral catalytic were investigated by the Perturbed Angular Correlations method (PAC), XRD, DTA and TGA. The hyperfine interaction was measured either during heat treatements or after annealing the samples at increasing temperatures up to 1200°C. All samples have presented a high fraction of crystalline phases at low temperatures. The yttria doped cubic zirconia has not shown the phase transition to the monoclinic phase. Pure zirconia powders produced in neutral hydrolysis and zirconia coatings produced in acid catalysis stabilized the tetragonal phase in a high fraction and up to high temperatures.Facultad de Ciencias Exacta

Quantum baker maps with controlled-NOT coupling

The characteristic stretching and squeezing of chaotic motion is linearized within the finite number of phase space domains which subdivide a classical baker map. Tensor products of such maps are also chaotic, but a more interesting generalized baker map arises if the stacking orders for the factor maps are allowed to interact. These maps are readily quantized, in such a way that the stacking interaction is entirely attributed to primary qubits in each map, if each subsystem has power-of-two Hilbert space dimension. We here study the particular example of two baker maps that interact via a controlled-not interaction. Numerical evidence indicates that the control subspace becomes an ideal Markovian environment for the target map in the limit of large Hilbert space dimension.Comment: 8 page

Sub-Heisenberg estimation of non-random phase-shifts

We provide evidence that the uncertainty in detection of small and deterministic phase-shift deviations from a working point can be lower than the Heisenberg bound, for fixed finite mean number of photons. We achieve that by exploiting non-linearity of estimators and coherence with the vacuum.Comment: Published version. Partially rewritten including further explanations and more numerical simulations. Updated reference

Coupling Bright and Dark Plasmonic Lattice Resonances

We demonstrate the coupling of bright and dark Surface Lattice Resonances (SLRs), which are collective Fano resonances in 2D plasmonic crystals. As a result of this coupling, a frequency stop-gap in the dispersion relation of SLRs is observed. The different field symmetries of the low and high frequency SLR bands lead to pronounced differences in their coupling to free space radiation. Standing waves of very narrow spectral width compared to localized surface plasmon resonances are formed at the high frequency band edge, while subradiant damping onsets at the low frequency band edge leading the resonance into darkness. We introduce a coupled oscillator analog to the plasmonic crystal, which serves to elucidate the physics of the coupled plasmonic resonances and to estimate very high quality factors (Q>700) for SLRs, which are the highest known for any 2D plasmonic crystal.Comment: 13 pages (in preprint), 4 figures, 1 tabl

Phase structure and thermal evolution in coating films and powders obtained by sol-gel process : Part II. ZrO2–2.5 mole% Y2O3

Powders and coatings of zirconia doped with 2.5 mole % yttria have been produced via the sol-gel route. The phase structure and subsequent thermal evolution in heating and cooling cycles have been investigated using mainly perturbed angular correlations spectroscopy. Thermal analyses and XRD as a function of temperature have also been performed to obtain complementary information. Upon heating, the amorphous gels crystallized into the tetragonal structure and showed the same hyperfine pattern and thermal behavior as observed in tetragonal zirconia obtained by the ceramic route: the two configurations of vacancies around zirconium ions denoted as t1 and t2 forms and their mutual t1 → t2 transformation. While the powder sample exhibited an incipient thermal instability above 1000 °C and underwent completely the t2 form to m–ZrO2 transition during subsequent, gradual cooling below 500 °C, the coating retained the tetragonal phase within the whole temperature range investigated. Hyperfine results suggest that the tetragonal phase stabilization is favored by the highly defective nature of the t1 form and consequently hardened by the availability of oxygen. The PAC derived activation energy for the fast diffusion of the oxygen vacancies inherent to the t2 form was determined as 0.54 ± 0.14 eV.Facultad de Ciencias Exacta