Fig. 3: The relationship of dopant, average structure, and local structure in KNN-based materials.

a A unit cell showing the atomic site occupation for KNN-Sb ceramic. b Normalized intensity of the A site for the KNN-Sb ceramic. Areas with high A site intensity are K rich. c Normalized intensity of the B site for the KNN-Sb ceramic. Areas with high B site intensity are Sb rich. d Polar vector map for KNN-Sb ceramic, the polar vectors (arrows) are given for each unit cell column. A unit cell with the polar vector direction along the [001] direction is of the T structure, and along the diagonal direction is of the O structure. e The enlarged areas of Na/Nb, K/Nb, Na/Sb, and K/Sb rich in (d). The different colour of unit cells shows the angle of polar vector direction off the [001] direction. f Polar vector map for KNN-Bi,Sb,Zr ceramic. The enlarged areas show the local average polar vector directions are slightly off the [001] direction (area VI) and along the [001] direction (area V), respectively. g The statistic percentage of polar vectors as a function of the polar vector angle (i.e., the deflection angle of polar vector off the [001] direction), based on (d, f).