Formation of dysprosium oxide from the thermal decomposition of hydrated dysprosium acetate and oxalate - Thermoanalytical and microscopic studies

Thermogravimetry, differential thermal analysis, X-ray diffractometry, gas chromatogra phy-mass spectrometry and scanning electron microscopy were used to characterize the course of Dy2O3 from hydrated acetate and oxalate of dysprosium in an atmosphere of air. The results show that Dy(CH3COO)(3) . 4H(2)O dehydrates completely in two steps at 90 and 150 degrees C and decomposes to Dy2O3 at 580 degrees C through a noncrystalline intermediate, Dy(OH)(CH3COO)(2), at 355 degrees C, Dy(O)(CH3COO) at 380 degrees C, and crystalline Dy2O2CO3 at 415 degrees C. For Dy-2(C2O4)(3) . 7H(2)O, the dehydration occurs in five steps at 100, 196, 227, 300 and 380 degrees C, forming an anhydrous oxalate, which is amorphous and unstable. The anhydrous oxalate immediately decomposes to Dy2O3 at 610 degrees C through two amorphous intermediates, Dy-2(CO3)(3) and Dy2O2CO3, that form at 436 and 455 degrees C, respectively. The crystalline oxide obtained from the acetate precursor contains large pores compared to the oxide obtained from the oxalate precursor. The volatile decomposition products from the acetate and oxalate precursors are water vapor, acetic acid, ketene, acetone and methane.