Because of its high ionic conductivity β-alumina is currently used as a solid electrolyte for gas sensors. In order to control the morphological propertes and sodium contents of powder used in such applications, it has been produced by two types of synthesis: by thermal denitrification and by the use of a gel. The various β-alumina crystallization mechanisms have been characterized. They illustrate the role played by certain precursors which, when present, are capable of affecting the ratio of β and β'' phases. Electrical conductivity measurements by AC technique at 300-500°C were carried out. Agering confirmed the much higher stability of the gel-prepared products.