Synthesis, thermal stability and magnetic properties of novel cadmium and praseodymium tungstate Cd0.25Pr0.50□0.25WO4 and its solid solutions

A novel cadmium and praseodymium tungstate, Cd0.25Pr0.50□0.25WO4, and its Cd0.25Pr0.50−0.25xRE0.25x□0.25WO4 solid solutions (where RE = Nd or Sm, □ are cationic vacancies, and x = 0.02, 0.10, 0.20 and 1.00), have been successfully prepared by high-temperature solid-state reaction of cadmium tungstate (CdWO4) with praseodymium ditungstate (Pr2W2O9) or an adequate Pr2W2O9/RE2W2O9 (RE = Nd, Sm) mixture. The resulting products were characterized by powder X-ray diffraction (XRD), differential thermal analysis with thermogravimetry (DTA-TG) and infrared spectroscopy (IR). The morphology of polycrystalline samples was determined using scanning electron microscopy (SEM). The Cd0.25Pr0.50□0.25WO4 tungstate and its solid solutions crystallize in the tetragonal scheelite type structure and melt congruently. The melting point of each Cd0.25Pr0.50−0.25xRE0.25x□0.25WO4 solid solution is slightly lower than the melting point of Cd0.25Pr0.50□0.25WO4 (1400 K). IR spectra of Cd0.25Pr0.50□0.25WO4 as well as Cd0.25Pr0.50−0.25xRE0.25x□0.25WO4 confirm that their crystal structure consists of WO4 tetrahedra. Electron paramagnetic resonance (EPR) studies of Cd0.25Pr0.50−0.25xNd0.25x□0.25WO4 solid solutions at low Nd3+ ions content showed the existence of isolated Nd3+ ions in paramagnetic state. The existence of neodymium antiferromagnetic dimers has been revealed for higher Nd3+ ions concentrations in the solid solutions under study.