Titanium Based Materials for High-Temperature Gas Sensor in Harsh Environment Application

Gas selective sensors that are capable of sensing at hot-gas environment are increasingly gaining importance for the monitoring of combustion and thermal processes releasing NO, NO2 and H2 containing hot gases at temperatures exceeding 600 °C. Despite some drawbacks, TiO2 is capable of operating as a gas sensor above 500 °C. In this context, Ni-doped TiO2, Co-doped TiO2 and Rh-doped BaTiO3 have been prepared by oxalate coprecipitation route and fully characterized. Co-doping of TiO2 promotes p-type behavior exhibiting good sensing properties to NO2 while Ni-doping displays the maintenance of n-type behavior and better H2-sensing properties at 600 °C. Rh-doped BaTiO3 shows excellent NO sensing properties at 900 °C.

Properties of Rare-Earth Substitution in Bi(Pb)-2223 Superconductor Prepared by Coprecipitation Method

The superconducting and structural properties of pure and rare-earth elements substituted in Bi (Pb)-2223 samples were investigated. All samples were fabricated by the oxalate coprecipitation (COP) method using metal acetates and oxalic acid as starting materials. The electrical and resistivity were measured by using the four-probe method, while phase purity and microstructural examination were performed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM). The pure sample has a critical temperature of (Tc zero) 100 K, which decreased to 98, 96 and 97 K for the Eu, Dy and Yb samples, respectively. At 77 K, the un-doped sample gives the highest Jc, which gradually decreases with rare-earth substitution as one move towards the right in the lanthanide series. XRD results reveal two main phases (Bi-2223 and Bi-2212) with decreased amounts of Bi-2223 phases by rare-earth substitution. SEM micrographs showed flaky grains but Yb showed better grain alignment compared with the other substitutions.