Theoretical positron lifetime values have been calculated systematically for most of the elements of the periodic table. Self-consistent and non-self-consistent schemes have been used for the calculation of the electronic structure in the solid, as well as different parametrizations for the positron enhancement factor and correlation energy. The results obtained have been studied and compared with experimental data, confirming the theoretical trends. As is known, positron lifetimes in bulk show a periodic behaviour with atomic number. These calculations also confirm that monovacancy lifetimes follow the same behaviour. The effects of enhancement factors used in calculations have been commented upon. Finally, we have analysed the effects that f and d electrons have on positron lifetimes.

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This work reports on the upgrades made to the direct emissivity measurement facility of the UPV/EHU. The instrumental improvements consist of, among others, a high-vacuum system and wider temperature range (300 − 1273 K). Methodological developments include a refined measurement equation with updated parameters and a reworked ISO-compliant uncertainty budget, and a Monte Carlo procedure for accurate calculations of total emissivities from spectral data. These upgrades have been demonstrated and validated in measurements of both metallic and ceramic materials. The results obtained in this work are applicable to similar experimental devices for emissivity measurements in order to report reliable emissivity data.

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