CATION ORDERING OBSERVED ON (MN0.88FE0.09)(TA0.86NB0.14)(2)O-6 - A MOSSBAUER AND X-RAY STUDY

Mossbauer spectroscopy and X-ray powder diffraction are used to show c ation ordering on a natural manganotantalite sample. By using electron microprobe analysis the chemical composition (Mn0.88Fe0.09) (Ta0.86Nb 0.14)(2)O-6 has been determined. The as-received sample is partially o rdered, as suggested by the low intensities of the superstructure refl ections in the X-ray diffraction pattern and by the existence of two d oublets in the Mossbauer spectrum. Heat treatment in vacuum (P congrue nt to 10(-5) Pa) at temperature T congruent to 1320 K induces cation o rdering as shown by the Mossbauer spectrum, and also evidenced by the X-ray diffraction pattern. (C) 1997 Published by Elsevier Science Ltd.