PbO-SiO2 Based Glass Coating of PbI2 Doped PbTe

Abstract

Thermoelectrics is one promising way of increasing the efficiency of machines and devices by reusing some of the waste heat produced. One obstacle for commercialization is the need to coat the materials to prevent sublimation and oxidation of the thermoelectric materials. Such coatings were designed for PbI2 doped PbTe using a (SiO2)0.68(PbO)0.3(B2O3)0.01(Na2O)0.01 based glass designed for operation at 500 °C. In this research various conditions of the coating process were examined. The effect of the atmosphere on the bonding and densification of the coating was studied using argon, vacuum and air. From the three air shows, the best bonding characteristics were from a better flow of glass and increased bonding between the oxidized PbTe layer and glass. This also created a PbO rich glass in the interface between the glass and the PbTe sample. The effect of 0, 3, and 6 wt. % NaCl additive to the solution was tested and showed that NaCl achieves better coverage due to high green body density, reaction of NaCl with the glass and removal of remaining CO2 from the glass in the form of decomposing Na2CO3. In addition, when testing the time and temperature, it was shown that the temperature of 520 °C was the minimum needed for high densification of the glass, but a duration shorter than 30 min did not allow for bonding of the glass to the substrate despite adequate densification. Finely, to obtain a well bonded coating with full coverage over the sample, the glass was coated with 6% NaCl in air at 520 °C for 30 min.

Structure and disorder in Pb‐Na metasilicate (PbO:Na2O:2SiO2) glasses: A view from high‐resolution 17O solid‐state NMR

“…Furthermore, a somewhat stronger preference of mixed NBO peak over Na‐O‐Si, particularly 1 Na 2 Pb‐O‐Si, leads to a decrease in the fraction of Na‐O‐Si (that are more prone to hydrolysis). This may increase the overall stability of the Pb‐bearing alkali silicate glasses 13,14 …”

“…12 PbO-SiO 2 glasses with Na 2 O can be utilized for coating of thermoelectric materials due mainly to their thermal stability. 13,14 Pb-bearing silicate glasses have been reported to be potential effective host materials for oxide nanoclusters 15,16 | 1319 KIM et al…”

“…The dissolution rate of Pb in Pb‐bearing alkali silicate glasses in contact with aqueous solutions is approximately 1 to 2 orders of magnitude lower than that of alkali cations (e.g., K + ), indicating an improved chemical durability of the glasses 12 . PbO‐SiO 2 glasses with Na 2 O can be utilized for coating of thermoelectric materials due mainly to their thermal stability 13,14 . Pb‐bearing silicate glasses have been reported to be potential effective host materials for oxide nanoclusters 15,16 and diverse lead‐bearing quantum dots (e.g., PbS) 17‐24 .…”