This compound is semiconducting and is
employed in small batteries used in portable electronic
devices. Magnesium bismuthate is prepared by the reaction
of sodium bismuthate with a soluble Mg salt.
MgBi2O6 can be classified as a transparent conducting
oxide (TCO) that possess an unusual combination
of properties; high transparency across most of the
visible spectrum, coupled with high-electrical conductivity.
TCO’s have a wide variety of applications,
including use in flat panel displays, solar cells,
energy-efficient windows, gas sensors, antistatic coatings,
and heating elements.
MgBi2O6 reveals temperature-
independent conductivity (0.01 S/cm2),
a negative Seebeck coefficient (20.025 mV/K), and an
optical band gap that falls at the low-energy end of
visible region (1.8 eV). This combination of attributes,
indicating that this compound is a degenerate n-type
semiconductor, a trait that has not previously been
reported in a Bi5+ oxide.
It consists of a ring structure of octahedral BiO62-
octagonal units with interspersed Mg2+ cations. Characterization
of polycrystalline samples of the trirutile
oxide Bi5+ revealed temperature-independent
conductivity (0.4 and 0.01 S/cm), a negative Seebeck
coefficient ( 0.035 and 0.025 mV/K), and an optical
band gap that falls at the low-energy end of visible
region (1.7 and 1.8 eV). This combination of attributes
indicates that this compound is a degenerate n-type
semiconductor, a property that has not previously
been observed in a Bi5+oxide.
The preparation of magnesium bismuthate, MgBi2O6,
was accomplished in a sealed PTFE-lined pressure vessel. The pressure vessel and contents were heated to
and held at 135°C for 2.5 days. The pressure vessel was
cooled to room temperature before opening. After separation
of the solid by filtration and drying at 60°C for
24 h, a dark brown powder was obtained.
