The microstructures of ferroelectric glass‐ceramics derived from (Pb,Sr,Ba)Nb2O6solid solutions have been investigated systematically using electron microscopy (TEM, SEM) and X‐ray diffraction (XRD). These data, together with the measured dielectric properties of the materials, have been correlated with both the sintering/devitrification conditions and compositional changes to the base glass. The low incidence of ferroelectric domains suggests that an increase in permittivity results from an increase in internal stress during grain growth. These domains were observed only in a few tetragonal structured crystals with grain sizes>1 μm. Their compositions were typically Sr‐rich and Ba‐depleted. For a given devitrification/crystallization temperature, the grain compositions and sizes are affected significantly by relatively minor compositional changes to the base glass network formers. The diffuse temperature dependence of permittivity is attributed to the fine‐grain (submicrometer) microstrucutres and the compositional range of solid solutions which arise during devit