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Synthesis, thermal stability and magnetic properties of novel cadmium and praseodymium tungstate Cd0.25Pr0.50a!0.25WO4 and its solid solutions
Ist Teil von
Thermochimica acta, 2013-09, Vol.568, p.95-103
Erscheinungsjahr
2013
Link zum Volltext
Quelle
Elsevier ScienceDirect Journals
Beschreibungen/Notizen
A novel cadmium and praseodymium tungstate, Cd0.25Pr0.50a!0.25WO4, and its Cd0.25Pr0.50a0.25xRE0.25xa!0.25WO4 solid solutions (where RE = Nd or Sm, a! 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 Cd0.25Pr0.50a!0.25WO4 tungstate and its solid solutions crystallize in the tetragonal scheelite type structure and melt congruently. The melting point of each Cd0.25Pr0.50a0.25xRE0.25xa!0.25WO4 solid solution is slightly lower than the melting point of Cd0.25Pr0.50a!0.25WO4 (1400 K). IR spectra of Cd0.25Pr0.50a!0.25WO4 as well as Cd0.25Pr0.50a0.25xRE0.25xa!0.25WO4 confirm that their crystal structure consists of WO4 tetrahedra. Electron paramagnetic resonance (EPR) studies of Cd0.25Pr0.50a0.25xNd0.25xa!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.