Fig. 1: Structure characterizations of Sr2−yCay(InSb)1−zSn2zO6:Fe3+.

a Schematic illustration of the composition transformation from SISO to CISO and to CSO via cation substitution. b XRD Rietveld refinement of SISO:Fe3+. The inset shows the cell parameters and volume variations of Sr2-yCayInSbO6:Fe3+ (y = 0–2). c HRTEM images with the SAED patterns of SISO:Fe3+ and CISO:Fe3+. d Raman spectra of Sr2-yCayInSbO6:Fe3+ (y = 0–2)