Exploring new methodologies for the identification of the morphotropic phase boundary region in the (BiNa)TiO^sub 3^-BaTiO^sub 3^ lead free piezoceramics: Confocal Raman Microscopy

On ferroelectrics materials, the piezoelectric activity is enhanced near the so-called morphotropic phase boundary (MPB) separating the rhombohedral and tetragonal phases in the binary phase diagram. Here, we report the identification of the morphotropic phase boundary (MPB) region in the (1-x)Na0.5Bi0.5TiO3-xBaTiO3 (BNT-BT) ceramic system by Confocal Raman Microscopy (CRM), emphasizing on the relationships between structure and piezoelectric properties. CRM results reveal the presence of the morphotropic phase boundary, between rhombohedral and tetragonal structures when BT concentration is close to 0.06-0.07. Raman spectroscopy can be used to rapidly identify the MPB on ferroelectric ceramics as seen in our model system (BNT-BT-based ceramics), since Raman spectra can be taken in few seconds, being then a very useful technique for material testing on industrial processes. Specifically, the methodology here showed represents an interesting way to correlate the micro and nanostructure with the properties in lead-free piezoceramics, which are controlled in part by the distribution of their different crystal phases. We believe that our results can benefit the understanding of BNT-BT ceramics expanding its applications range.