Microstructure and properties of plasma sprayed Al-doped YSZ coatings

Abstract

The influence of alumina additive from 1 to 5 wt. % upon the microstructure and ionic conductivity of ZrO2-8 mol % Y2O3 (YSZ) ceramics, deposited by means of plasma spray technology, was investigated. Plasma sprayed films have been analysed using scanning electron microscopy (SEM) and X-ray analysis (XRD). The microstructural examination reveals that alumina addition decreases the porosity and microcracks of plasma sprayed YSZ. Analysis of SEM micrographs shows that the amount of 5 wt. % alumina substantially improves the microstructure of plasma sprayed zirconia. The crystal structure of all plasma sprayed samples consists of cubic zirconia and α-alumina. By the data of ionic conductivity measurements, no significant influence of annealing at 1073 K for 10 h was noticed on characteristic temperature dependences of σ for plasma sprayed YSZ. Alumina doping from 2 to 5 wt. % considerably increases the ionic conductivity of plasma sprayed zirconia. The higher values of ionic conductivity were obtained when 5 wt. % of Al2O3 powder was added to YSZ.

Improvement of plasma-sprayed YSZ electrolytes for solid oxide fuel cells by alumina addition

“…Many post-densification processes have been applied to improve APS YSZ electrolyte, including acidic phosphate solution sealing [12], nitrate decomposition [11,13], sol immersion [14], laser glazing [15], and spark sintering [16]. At present, many investigations have been carried out to improve the gas permeability and ionic properties of YSZ thin films using alumina addition [2,[17][18][19][20][21]. Initial YSZ powder with 3-4 wt.% of Al 2 O 3 addition allows one to produce SOFC electrolyte layer with higher value of bulk density [20] and with practically no open porosity.…”

“…The reduction of SOFC operating temperatures down to 973-1,073 K is another important problem, which determinates their practical use. The use of thin electrolyte films is a possible way of removing this problem [2].…”