Contributions to the study of inorganic nonstoichiometric compounds. 10

Quenched samples of the high temperature form of Ta2O5 with Ti contents of 0 until 6.7 at-% (SIGMAMe=100 %) were investigated in the metastable region from 20 to 14000C with a continuously registrating guinier-camera which was equiped with a special sample heating divice:There are 3 roomtemperature-phases:H(triclinic), H1 (monoclinic), H2(monoclinic), and 3 high temperature phase:H'(triclinic), H2'(monoclinic), and H3(tetragonal). In the regions between H and H1 as well as H1 andH2 diagrams of both phases could bo observed together on the X-ray photograph; these regions disappeare at temperatures higher than approximately 3100C. With increasing temperatures the following phase transitions occure: H → H' → H2' → H3, H1 → H →H2' → H3, H2 → H1 → H2' → H3, H2 → H2' → H3. Electronmicroscopic investigations of a sample with 6.7 at-% Ti gave no indication to the existence of 'shear planes'. By means of the present results various possibilities of the incorporation of Ti in the H-Ta2O5 lattice are discussed. (author)