Figure 5
(a) θ-2θ XRD data collected as a function of time (from 0 min up to 4 h), at a temperature T = 510 °C, under atmospheric conditions, starting from an initial parent glass under powder form, and displayed in the 25–38° 2θ range. The (■) symbols correspond to the main cubic Bi0.8Nb0.8Te2.4O8 crystal phase (Ia-3 space group), whereas the ◇ symbols highlight the appearance of the secondary BiNbTe2O8 orthorhombic phase, after only 20 min of heating treatment. (b) Average Raman spectra recorded for both the cubic (bottom) and orthorhombic (top) phases. Insert: Sketch describing the cross-section of a bulk laser ceramic sample and indicating the location of the probed areas for the Raman analysis, spotted by the (x) and (•) symbols.
