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Magnesium bismuthate Chemical Properties,Usage,Production

Description

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.

Physical properties

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 BiO₆^2- 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.

Preparation

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.