  We present atmospheric parameters for about 300 stars of different chemical
composition, whose spectra will be used to study the galactic enrichment of Fe
and light elements. These parameters were derived using an homogenous iterative
procedure, which considers new calibrations of colour-\teff\ relations for F, G
and K-type stars based on Infrared Flux Method (IRFM) and interferometric
diameters for population~I stars, and the Kurucz (1992) model atmospheres. We
found that these calibrations yield a self-consistent set of atmospheric
parameters for \teff$>4400$~K, representing a clear improvement over results
obtained with older model atmospheres. Using this \teff-scale and Fe
equilibrium of ionization, we obtained very low gravities (implying
luminosities incompatible with that expected for RGB stars) for metal-poor
stars cooler than 4400~K; this might be due either to a moderate Fe
overionization (expected from statistical equilibrium calculations) or to
inadequacy of Kurucz models to describe the atmospheres of very cool giants.
Our \teff\ scale is compared with other scales recently used for metal-poor
stars; it agrees well with those obtained using Kurucz (1992) models, but it
gives much larger \teff's than those obtained using OSMARCS models (Edvardsson
et al. 1993). This difference is attributed to the different treatment of
convection in the two sets of models. For the Sun, the Kurucz (1992) model
appears to be preferable to the OSMARCS ones because it better predicts the
solar limb darkening; furthermore, we find that our photometric \teff's for
metal-poor stars agree well with both direct estimates based on the IRFM, and
with \teff's derived from H$\alpha$\ wings when using Kurucz models.
