Morphology and the Structural Study of the TTB Ferroelectric Sr2(1-x)Na(1+x)GdxNb5O15 (SNGN)

We synthesized The nanopowders ferroelectric Sr2(1-x)Na(1+x)GdxNb5O15 by solid-state method. Using X-ray diffraction (XRD) and scanning electron microscopy (SEM) technique we studied the Sr2(1-x)Na(1+x)GdxNb5O15 (SNGN) ceramics over the composition range 0 ≤ x ≤ 1. The X-ray results reveal an orthorhombic phase, with space group Pmmm for 0 ≤ x ≤ 0.8 and a tetragonal phase, with space group P4mm (a = b = 12.3343 Å et c = 3.9778 Å), for 0.9 ≤ x ≤ 1. These results are confirmed by the SEM technique who provide strong evidence of the reduction of the disorder in the TTB structure when going from Sr2+ to Gd3+ (from x = 0 to x = 1). This disorder is connected to the orthorhombic distortion, which is reduced when going from orthorhombic to tetragonal phase