Synthesis and thermal, optical and magnetic properties of new Mn 2+ -doped and Eu 3+ -co-doped scheelites

A series of Mn 2+ -doped and Eu 3+ -co-doped calcium molybdato-tungstates, i.e., Ca 1−3x−y Mn y ⌷ x Eu 2x (MoO 4 ) 1−3x (WO 4 ) 3x (0 < x ≤ 0.2222 when y = 0.0200 and 0 < y ≤ 0.0667 when x = 0.1667, ⌷ represents vacancy) materials were successfully synthesized via high-temperature annealing. XRD results confirmed the formation of single, tetragonal scheelite-type phases (space group I 4 1 / a ). A change in both lattice constants ( a and c ), lattice parameter ratio c / a and progressive deformation of MoO 4 /WO 4 tetrahedra with increasing Eu 3+ as well as Mn 2+ contents were observed. The melting point of doped materials is lower than the melting point of pure matrix, i.e., CaMoO 4 . New materials exhibit strong absorption in the UV range. They are insulators with the optical direct band gap ( E g ) higher than 3.50 eV. The E g values nonlinearly change with increasing dopants concentrations. EPR measurements allowed to establish the nature of magnetic interactions among Mn 2+ ions. Additionally, EPR spectra were sensitive on both parameters: Mn 2+ and Eu 3+ concentration.