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Synthesis, Crystal Structure, and Magnetic Properties of Pyrochlore‐Type Eu 2 Ta 2 (O,N) 7+ δ
Author(s) -
Anke Björn,
Hund Sophie,
Lorent Christian,
Janka Oliver,
Block Theresa,
Pöttgen Rainer,
Lerch Martin
Publication year - 2017
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201700024
Subject(s) - pyrochlore , europium , crystallography , materials science , paramagnetism , electron paramagnetic resonance , tantalum , orthorhombic crystal system , fluorite , analytical chemistry (journal) , phase (matter) , crystal structure , chemistry , nuclear magnetic resonance , luminescence , physics , optoelectronics , organic chemistry , chromatography , metallurgy , quantum mechanics
Pyrochlore‐type Eu 2 Ta 2 (O,N) 7+ δ phases were prepared by reaction of ammonia with an amorphous europium tantalum oxide precursor. 151 Eu Mössbauer and EPR spectroscopy as well as magnetic susceptibility measurements point to the presence of exclusively Eu 3+ . For phase‐pure samples (X‐ray powder diffraction), the nitrogen content varies between 1.0 and 1.8 wt %, leading to compositions in the range Eu 2 Ta 2 O 7.1 N 0.6 – Eu 2 Ta 2 O 6.5 N 1.0 . Pyrochlore‐type phases are structurally derived from the fluorite type with 1/8 of the anions missing, resulting in an ideal composition A 2 B 2 X 7 . In Eu 2 Ta 2 (O,N) 7+ δ the excess anions partly occupy these vacancies. The prepared phases are colorless with a direct optical bandgap of 4.3 eV and they show the typical Van Vleck paramagnetic behavior known for trivalent Eu atoms.