Thermal decomposition of lanthanum selenate pentahydrate in air and nitrogen

Thermogravimetric studies, supported by IR and X-ray diffraction measurements, were carried out for La2(SeO4)3 · 5H2O in order to establish its decomposition scheme under various experimental conditions. Several analytical methods were tested for the simultaneous determination of (Se(IV) and Se(VI) in the quenched samples. TG weight losses and analyses of the solid intermediates indicated that after dehydration La2(SeO4)3 decomposes in nitrogen mainly to oxyselenite(IV) compoundsvia the normal selenite(IV) but in air the oxyselenate La2O2SeO4 was detected as one of the intermediates. The final product of the thermal degradation is La2O3. TG curves of La2(SeO4)3 · 5H2O were also compared with those obtained for the isostructural neodymium compound.