The development of triple oxide semiconductor nanostructures (NS) with special optical window is critical for the optoelectronics and the luminescent industry. The present article describes the synthesis of Smx:Gd(1−x)@SrO (x = 0.4, 0.6, 0.8) NS by simple Coprecipitation method. The NS were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), SEM–EDS (energy dispersive spectra), Fourier transform infrared (FT-IR), UV–visible, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller analytical methods. The results of the powdered XRD pattern revealed the formation of mixed-phase of hexagonal crystal structure, with grain size between 62 and 78 nm. Redshift in optical absorption spectra for the Sm3+ doped Gd(1−x) SrO NS appeared when compared to Gd(1−x) SrO NS. Photoluminescence (PL) spectroscopy demonstrated broad deep defect levels in Smx: Gd(1−x) SrO NS when compared to Gd(1−x) SrO NS. PL studies of Gd0.6, SrO exhibited three emission peaks detected at 373.6 nm, 382.1 nm, and 392.7 nm when excited at 325 nm. PL studies of Smx: Gd(1−x) SrO NS (x = 0.8) showed four emission peaks appeared at 415 nm (violet), 472 nm (blue), 532.1 nm (green) and 569.6 nm (yellow) due to f–f transition of Sm3+ in 4f5 configuration. Higher values of dielectric constant (3.86 × 104), dielectric permittivity (103–105) resulted for the Smx:Gd(1−x)@SrO (x = 0.8) NS with negligibly small dielectric loss (< 0.03) when compared to Gd0.6 SrO NS. The synthesised materials demonstrated excellent luminescence properties with good dielectric properties therefore these materials could be good candidates to be used as high-luminescent devices.Graphical Abstract