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 microscop y were used to characterize the course of Dy2O3 from hydrated acetate and oxalate of dysprosium in an atmosphere of air. The results show th at 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 nonc rystalline intermediate, Dy(OH)(CH3COO)(2), at 355 degrees C, Dy(O)(CH 3COO) 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 i s amorphous and unstable. The anhydrous oxalate immediately decomposes to Dy2O3 at 610 degrees C through two amorphous intermediates, Dy-2(C O3)(3) and Dy2O2CO3, that form at 436 and 455 degrees C, respectively. The crystalline oxide obtained from the acetate precursor contains la rge pores compared to the oxide obtained from the oxalate precursor. T he volatile decomposition products from the acetate and oxalate precur sors are water vapor, acetic acid, ketene, acetone and methane.