Eu2O3 role in the optical and photoluminescence properties of $$50{\text{ SiO}}₂ - 7{\text{ MgO}} - { }20{\text{ ZnO}} - { }\left( {23 - x} \right){\text{ La}}₂ {\text{O}}₃ - x{\text{ Eu}}₂ {\text{O}}₃$$ nano-crystalline thin films

Nano-crystalline (50{ ext{ SiO}}₂ ; - ;7{ ext{ MgO}}; - ;{ }20{ ext{ ZnO}}; - ;left( {23 - x} ight);{ ext{La}}₂ { ext{O}}₃ - x{ ext{Eu}}₂ { ext{O}}₃ left( {0.0; le ;x; le ;4;{ ext{ mol}}\% .} ight)) termed as (Eu-SMZL) thin films have been synthesized by highly acidic sol–gel technique and calcined at 450 °C for 2 h. The nano-porous Eu-SMZL films showed the improved structure and morphology with increasing Eu2O3 content. The XRD and FTIR investigation proved an increase in the crystallinity and changes in the internal structure with the increase in Eu3+ level. The photoluminescence (Pl) result agrees with the XRD, proving the increase in the crystallinity. The transmittance (T) and absorbance (A) spectra have been measured within 300–2000 nm spectral range. The absorption coefficient ((alpha)) and refractive index (n) have been estimated. It is worth to mention that the increment of ({ ext{Eu}}₂ { ext{O}}₃) at the expense of La2O3 shifts the absorption edge to the long wavelength side (red shift) which leads to a decrement in the band gap ((E_{{{ ext{opt}}}})) values while the (n) values increases. This behavior of (n) is well discussed in terms of the glass density (Gd), molar volume (Vm), electronic polarizability ((alpha_{{{ ext{el}}}})) and optical basicity (({Lambda })). Furthermore, the single oscillator model helps us to investigate the static index of refraction ((nleft( 0 ight))), energy of single oscillator ((E_{{ ext{o}}})), and dispersion energy ((E_{{ ext{d}}})).