Environmental barrier coating for silicon based substrates

An article comprises a silicon based substrate, a bond layer and a protective top layer. The top layer is selected from the group consisting of rare earth disilicates, yttrium disilicates, rare earth monosilicates, yttrium monosilicates, silica and mixtures thereof. The protective layer described above is used in combination with a bond layer provided between the protective layer and the silicon based substrate which functions as oxygen getter and includes an oxygen gettering agent. By oxygen gettering agent is meant a refractory metal oxide former which forms an oxide at operational condition of (high temperature and aqueous environment) having a melting point of greater than 1500°C wherein the negative free energy of formation of the refractory metal oxide from the refractory metal is more than 100 Kcal/mole. Suitable oxygen gettering agents include silicon and other refractory metals. An oxygen gettering agent may also be added to the protective layer.