A coated substrate is provided that includes an environmental barrier coating on (e.g., directly on) a surface of a substrate (e.g., a ceramic matrix composite). The environmental barrier coating caninclude a barrier layer having a refractory material phase and a silicon-containing glass phase. The silicon-containing glass phase may be a continuous phase within the barrier layer (e.g., a breathable grain boundary of the barrier layer), or may be a plurality of discontinuous layers dispersed throughout the refractory material phase. The refractory material phase can include a rare earth silicate material having a rare earth component at a first atomic percent, while the silicon-containing glass phase comprises the rare earth component at a second atomic percent that is less than the firstatomic percent. Methods are also provided for forming a barrier layer on a substrate.