Preparation and corrosion resistance of graded glass coating on PbTe

Lead telluride (PbTe) is a promising material for the thermoelectric power generation system using combustion heat from municipal solid waste. Because the combustion gas from solid waste incinerator generally contains corrosive substances such as HCl and H₂SO₄, the corrosion resistance of PbTe becomes important for its thermoelectric application. In the present study, SiO₂-B₂O₃-Na₂O-ZnO system glasses were coated on PbTe in order to improve the corrosion resistance. Addition of PbO and TeO₂ to this system glass significantly improved the adhesion of the glass as well as the oxidation resistance of glass-coated PbTe. However, the addition of PbO and TeO₂ degraded the corrosion resistance of the glass coating because the PbO and TeO₂ reacted with HCl at high temperature to form volatile chlorides. In order to incorporate the corrosion resistance and adhesion of glass coating, a two-layer glass was coated on PbTe, in which the inner layer contains 60 mass%PbO·TeO₂ while the outer layer contains no PbO·TeO₂. Corrosion experiments showed that the glass coating with the graded PbO·TeO₂ content exhibited excellent adhesion and corrosion resistance at an O₂-HCl-Ar atmosphere.