A Closed-System Potentiostatic Technique Employing a Solid Electrolyte for the Investigation of Thermal Stability of Praseodymium Oxides

• Published in: Materials Transactions, JIM Vol. 31; no. 11; pp. 999 - 1004
• Main Authors: Yao, Shinya, Uchida, Hidetoshi, Kozuka, Zensaku
• Format: Journal Article
• Language: English
• Published: Sendai The Japan Institute of Metals 1990; Japan Institute of Metals
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; isothermal hysteresis; Other topics in thermal properties of condensed matter; phase transition; Physics; potentiostatic technique; praseodymium oxides; rare-earth oxides; solid electrolyte; stabilized zirconia; Thermal properties of condensed matter; thermal stability; Measuring instrument; Phase transformation; Oxygen; Thermal hysteresis; Solid electrolyte; Praseodymium Oxides; Stabilized zirconia; Experimental study; Thermal stability; Lanthanide Oxides
• ISSN: 0916-1821; 2432-471X
• DOI: 10.2320/matertrans1989.31.999

An oxygen analyzer with a closed system was set up to investigate the thermal stability of praseodymium oxides. It was composed of a circulation pump, specimen, and an electrochemical oxygen pump: Pt, air/ZrO2(+CaO)/Ar+O2 gas, Pt. Praseodymium oxide was heated up and successively cooled down at a constant rate in circulating Ar gas, in which the oxygen chemical potential was maintained at a constant value by a potentiostatic operation. The phase transition was monitored using the change in an electrical current passing through the oxygen pump. Pr5O9⇔Pr9O16 and Pr9O16⇔Pr7O12 occured gradually at first and then rapidly with time, which are consistent with the isothermal chemical hysteresis reported in the literature. The temperature of the phase transition: PrOx(σ)→Pr2O3(A), i.e., CaF2-related structure→A type sesquioxide, was very dependent on the heating run numbers, implying that at least two factors affect the relative stability of the two phases. The closed-system potentiostatic technique permits measurements with such a high sensitivity that 10−8∼10−9 g of oxygen is detectable, and therefore, it may be applicable for the investigation of micro-reactions.