Structural and Thermodynamic Stability of the “1111” Structure Type: A Case Study of the EuFZnPn Series

Two
new compounds with the LaOAgS structure, EuFZnAs (1)
and EuFZnSb (2), were obtained via solid state reaction.
Both compounds are tetragonal (P4/nmm) with the cell parameters a = 4.1000(1) Å
and c = 9.0811(1) Å for 1 and a = 4.2852(1)­Å and c = 9.4238(1)­Å
for 2. The absence of their phosphide analog can be explained
based on crystal chemical considerations as well as on quantum-chemical
estimates of their thermodynamic stability with respect to EuF2 and EuZn2Pn2. The magnetic response
of 1 and 2 is ascribed to the presence of
Eu2+ ions. Both compounds are paramagnetic down to low
temperatures, where they order antiferromagnetically at ∼5
K and ∼3 K, respectively. They are narrow-gap semiconductors,
and EuFZnSb demonstrates a relatively high value of the Seebeck coefficient.