Cation substitution for tunable electronic, optical and scintillation properties of Pb1-xCaxWO4 materials: A density functional theory study

Abstract

Based on the density functional theory (DFT) calculations, we report on the influence of the cation substitution on the electronic, optical and scintillation properties of Pb1-xCaxWO4 with x = 0, 0.25, 0.5, 0.75 and 1). The DFT calculations are made using the FP-LAPW method and different approximations to gain a reliable band gap value and accurate electronic and optical properties. The calculated band structure and density of states show that, pure PbWO4 and CaWO4 materials have, respectively, band gap energy of 4.5 eV and 6.1 eV which are very close to the experimental data and other theoretical predictions. For Pb1-xCaxWO4 cases, the obtained values of band gaps are very close to that one of pure PbWO4. Besides that, it is found that, the cation substitution can provide high rates of transmittance between 90.27% and 92.39% in the emission range which is an advantage for the scintillation properties. This substitution allows one to tune the reflectivity, the refractive index and the related scintillation properties and, in addition, promotes narrow and tunable discrete electronic bands in the conduction and valence bands which enhance the charge localization and improve the light yield. Our results also demonstrate the possibility of using the cation substitution as a new and potential route to control the number and width of the energy gaps between the discrete conduction (valence) bands. These findings suggest considering these materials, especially for the cases of Pb1-xCaxWO4 with x higher 0.5 as appropriate candidates for tunable fast intra-band luminescence applications.

Keywords

• Cation substitution
• Tunable electronic and optical properties
• Fast intra-band luminescence
• GGA+ mBJ approximation
• Lead-Calcium tungstate alloys