Trend Pembentukan Piroklor Ln2Te2O7, Ln = La, Nd, Eu dan Gd

As an extension of Weber, F. A. and Schleid, T. work, attempts to prepare Ln 2 Te 2 O 7 , Ln = La, Nd, Sm, Eu and Gd using the solid state reaction have been conducted. The products were characterized using X-ray powder diffraction methods. La 2 Te 2 O 7 (a = 11,3821 A) was formed with impurities TeO 3 , La 2 O 2 Te and La 2 TeO 6 , while for Nd 2 Te 2 O 7 (a = 11,1564 A) the impurities were TeO 3 , Nd 2 O 2 Te and Nd 2 TeO 6 . Both were decomposed above 850 °C. Neither Eu nor Gd formed pyrochlore, instead mixtures with dominant phases of Ln 2 Te 2 O 7.2 . It could be supposed that ionic radii of Eu and Gd too small to stabilize pyrochlore structure. Attempts to prepare Bi 2 Te 2 O 7 and Pb 2 Te 2 O 7 have not successful yet.