Stacking Variants and Superconductivity in the Bi–O–S System

High-temperature
superconductivity has a range of applications
from sensors to energy distribution. Recent reports of this phenomenon
in compounds containing electronically active BiS2 layers
have the potential to open a new chapter in the field of superconductivity.
Here we report the identification and basic properties of two new
ternary Bi–O–S compounds, Bi2OS2 and Bi3O2S3. The former is non-superconducting;
the latter likely explains the superconductivity at Tc = 4.5 K previously reported in “Bi4O4S3”. The superconductivity of Bi3O2S3 is found to be sensitive to the
number of Bi2OS2-like stacking faults; fewer
faults correlate with increases in the Meissner shielding fractions
and Tc. Elucidation of the electronic
consequences of these stacking faults may be key to the understanding
of electronic conductivity and superconductivity which occurs in a
nominally valence-precise compound.