X-ray diffraction in the Bragg-Brentano configuration (“XRD”) is a very established method. However, experimental evidence concerning its significant information depth, i.e. microstructure components from which maximum depth can affect the information evaluated from the acquired diffraction pattern, are scarce in the scientific literature. This depth is relevant to all XRD measurements performed on compact samples, especially layered composites and samples showing a crystallographic texture evolution. This article provides experimentally determined upper and lower limits to the significant information depth: XRD patterns acquired from a compact crystal layer through a layer of compact, amorphous glass indicate that the significant information depth of XRD using Cu Kα1 and Kα2 radiation is very likely larger than 48 μm, but smaller than 118 μm, in a material of the composition Mg2Al4Si5O18 with a density of ca. ~2.6 g/cm3. The depth of 48 μm correlates to the depth larger than the layer of material from which 90% of the reflected X-rays originate at 2Θ = 25.8°.
