SiC(m)/SiC(f) ceramics matrix composites (CMC) are intended to be used more and more frequently to make parts of the next generations of aircraft engines, located in hot zones. However, in operating conditions (combustion environment, rich in water vapor), these materials are degraded by oxidation and volatilization phenomena. In order to increase the lifetime of these composites, a protective coating acting as an environmental barrier (EBC) is deposited on the surface of a CMC/Bond coat (Silicon) architecture, generally by plasma spraying technics or liquid coating processes. In regard to the extreme environmental conditions in an aircraft engine (mechanical loading and corrosion degradation), the development of EBCs focuses on materials based on rare earth silicates, as yttrium or ytterbium mono or disilicates (RE2Si2O7 and RE2SiO5). They are thermochemical and thermomechanical compatible with the whole architecture. Nevertheless, the presence of free silicon, main constituent in the bond coat, limits operating temperatures to get a well sintered and dense barrier, required to fulfill their role of EBC. The objective of this work is to identify new systems including these rare earth silicates, with enhanced protection efficiency. To get dense coating, starting from powders, while using a natural sintering process, the concept called "self-healing" is applied to EBCs. One way was to introduce alumina in different quantities through the use of various compounds ; a reactive sintering and/or a transient liquid phase are involved in this densification process. The densification ratio is thus increased after a natural sintering at temperatures lower than 1400°C, possibly compatible with the deposition conditions of many methods. Experiments showed that the best densification is reached for an optimum alumina content and respectively too much of alumina may prevents the densification process. Thermodynamic calculations on the solid equilibria were useful to help in the choices of the nature and quantities of several mixed constituents. Changes in compositions were selected to preserve the stability at high temperature in a humid environment of the EBC material, while increasing the resistance to corrosive species known as molten sand (calcium magnesium alumino silicate : CMAS).