We propose to acquire operando time-resolved Full-Field Diffraction X-ray Microscopy (sFFDXM) images of AlN/Sapphire Surface Acoustic Wave (SAW) devices. Recent studies have shown that the AlN/Sapphire bilayer structure for SAW sensors is promising as it can withstand higher temperatures and operate at higher frequencies than Langasite which is the current standard for high-temperature applications. [1] A timely and spatially resolved characterization of the wave propagation in the piezoelectric layer and the substrate will extend our physical description of the currently misunderstood sources of losses of SAW based sensors that can operate at high temperatures. This can be done with the material selectivity and resolution of sFFDXM. This proposal builds upon the lessons learnt from the beamtime related to proposal ME-1648 and the in-house experiment BLC 15862.