A polar glass-ceramic containing Sr-fresnoite Sr2TiSi2O8 (STS) as single crystalline phase was developed through the controlled crystallization of a parent glass composition containing SrO, TiO2, SiO2, K2O, and Al2O3. The objective of this work is to obtain a piezoelectric substrate exhibiting a well-defined orientation of the polar direction of the STS crystals over a depth suitable for the design of surface acoustic waves (SAW) devices. For that purpose, the crystallization mechanism of the parent glass was first studied by Differential Scanning Calorimetry (DSC). Based on this study, heat treatments were applied to transform the glass into glass-ceramics. Two aspects were investigated: i). The influence of the surface state of parent glass and of its environment on the nucleation of preferentially orientated STS crystals at the surface of the parent glass; ii). The growth of a preferentially orientated crystallized layer from the surface into the bulk. The microstructures of resulting glass ceramics were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). We demonstrate that growth of the surface crystallized layer is governed by diffusion mechanisms through a transition glass composition separating the crystalized layer and the subjacent parent glass. The control of the growth rate of the crystalline layer plays the key role to keep a high and constant orientation of the (002) STS plans parallel to the surface of the substrate.