Sintering and microstructure characterisation of metal oxide codoped yttria stabilised zirconia for thermal barrier coating applications

Abstract

In this study, yttria stabilised zirconia (YSZ) was codoped with six metal oxides of different valence, atomic mass and ionic radius in order to investigate microstructural changes as a result of doping. A mechanical alloying process was used to produce the powder blends which were subsequently sintered at 1500°C for 120 h. A detailed microstructural study was conducted to characterise both the alloyed powders and sintered bulk materials. It was found that the occurrence of oxygen vacancies played a crucial role in stabilising the cubic and tetragonal phases and the presence of cations with larger ionic radius played a similar effect. Furthermore, the use of oxygen vacancy in the pseudo binary phase diagram was able to provide a general predication of phase transformation; however, an equivalent oxygen vacancy taking into consideration both the oxygen vacancies and dopant ionic size may give a more accurate prediction of microstructure.

Keywords:

• YTTRIA STABILISED ZIRCONIA
• DOPING
• SINTERING
• TERNARY SYSTEM
• MECHANICAL ALLOYING
• MICROSTRUCTURE CHARACTERISATION