Doping effect and vacancy formation on ionic conductivity of zirconia ceramics

• Published in: The Journal of physics and chemistry of solids Vol. 69; no. 2; pp. 386 - 392
• Main Authors: Yeh, Tsung-Her, Chou, Chen-Chia
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.02.2008; Elsevier
• Subjects: A. Ceramics; A. Oxides; Condensed matter: structure, mechanical and thermal properties; D. Defects; D. Electrical properties; Diffusion in solids; Exact sciences and technology; Physics; Self-diffusion and ionic conduction in nonmetals; Transport properties of condensed matter (nonelectronic); A. Ceramics; A. Oxides; D. Defects; D. Electrical properties; Grain boundaries; Scanning electron microscopy; Phase transformations; Ionic conductivity; Doping; Niobates; XRD; Ionic radius; Vacancy density; Zirconium oxide; Defect formation
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2007.07.117

Doping effect and vacancy formation on ionic conductivity of ZrO 2 ceramics doped with RENbO 4 (RE=Yb, Er, Y, Dy) were investigated using X-ray diffractometry, scanning electron microscope and corresponding ionic conductivity were evaluated using impedance spectroscopy in this work. The results show that defect distribution can be correlated with the phase transformation behavior modified by ionic radius of dopants. The total conductivity of 5 mol% RENbO 4-doped ZrO 2 (3Y) comprises the intragrain and grain boundary (GB) conductivity. The intragrain conductivity of 5 mol% RENbO 4-doped ZrO 2 (3Y) are lower than 3 mol% Y 2O 3-doped ZrO 2 (3Y-TZP) and 8 mol% Y 2O 3-doped ZrO 2 (8YSZ). The additions of Nb 2O 5 to ZrO 2 (3Y) increase average lattice binding energy and activation energy, and the amount of oxygen vacancies was decreased. The average radius of oxygen vacancies of 5 mol% RENbO 4-doped zirconia (3Y) were smaller than that of 8YSZ identified using hard-sphere model. The results imply that a specific doping content in zirconia which contributes a maximum content of non-interfering oxygen vacancies, the average radius of doping ions close to that of Zr 4+ and average binding energy as smaller as possible help obtain the highest conductivity of zirconia. To acquire an appropriate operation condition in the application of solid oxide fuel cell, electrical properties, phase transformation behavior and related mechanical properties need to be compromised.