New Gd 3+ and Mn 2+ -Co-Doped Scheelite-Type Ceramics—Their Structural, Optical and Magnetic Properties.

New Gd³⁺- and Mn²⁺-co-doped calcium molybdato-tungstates with the chemical formula of Ca_1−3x−yMn_y▯_xGd_2x(MoO₄)_1−3x(WO₄)_3x (labeled later as CaMnGdMoWO), where ▯ denotes vacant sites in the crystal lattice, 0 < x ≤ 0.2500 and y = 0.0200 as well as 0 < y ≤ 0.0667 and x = 0.1667 were successfully synthesized by high-temperature solid-state reaction method and combustion route. Obtained ceramic materials crystallize in scheelite-type structure with space group I4₁/a. Morphological features and grain sizes of powders under study were investigated by SEM technique. Spectroscopic studies within the UV-vis spectral range were carried out to estimate the direct band gap (E_g) and Urbach energy (E_U) of obtained powders. EPR studies confirmed the existence of two types of magnetic objects, i.e., Mn²⁺ and Gd³⁺ ions, and significant antiferromagnetic (AFM) interactions among them. [ABSTRACT FROM AUTHOR]