“…The radius of Eu 3+ is quite similar to that of Gd 3+ and Y 3+ , thereby forming a solid solution. The radii of Eu 3+ , Gd 3+ , and Y 3+ are 0.947, 0.94, and 0.900 Å , respectively [11,12]. The crystallite size (D) of the annealed (Y 0.5 Gd 0.5 ) 0.94 Eu 0.06 VO 4 phosphors is calculated from the Scherrer formula: D = (0.9l)/(b cos u), where l is the wavelength of radiation, u is the angle of the diffraction peak, and b is the full width at half maximum of the diffraction peak (in radian) [13].…”