The goal of this work is to evaluate the potentialities of MWs for synthesising sodalite/cxA12O3 membranes on tubular supports using hydrothermal conditions. The method allows the synthesis of promising surface films and infiltrated membranes. However, with the conditions used in this work, the dissolution of the [alpha]-alumina support revealed a disturbing phenomena for both the reproducibility and scaling-up of the direct membrane synthesis. In order to overcome this problem, another indirect strategy has been also considered: the pre-seeding/secondary growth method which allowed the synthesis of larger and homogeneous samples with a good reproducibility. The membrane quality was evaluated by single gas permeation studies with both N2 and He. In the studied range of temperature 20-165°C, gas transport was essentially governed by adsorption and surface diffusion, yielding a maximum selectivity [alpha]He/N2 of 6.2 at 115°C, although a selectivity lower than 2 was measured for a ZSM-5/[alpha]A12O3 membrane in similar conditions.