Study of the structural and phase state of ceramics synthesized from 6YSZ - Al2O3 – HfO2 by semi–dry pressing followed by sintering in vacuum

Abstract

The study investigates the properties of 6YSZ – Al₂O₃ – HfO₂ powder mixture and the resulting ceramics obtained by semi-dry pressing followed by sintering in vacuum. X-ray fluorescence spectrometry revealed the primary constituents as zirconium (81%), aluminum (8.7%), yttrium (5.7%), and hafnium (3.5%). The average particle diameter was 0.5 μm, with specific surface area and bulk weight recorded at 18,535 cm²/g and 0.84 g/cm³, respectively. X-ray phase analysis indicated a predominance of monoclinic zirconium dioxide. Sintering at 1400-1600°C transformed the phase composition, enhancing density and microhardness, with values peaking at 5.8 g/cm³ and 12.1 GPa at 1600°C. This process also increased the tetragonal phase content to 63%. The ceramics exhibited the highest crack resistance at 1600°C, attributed to the stabilized tetragonal zirconium dioxide. Microstructural analysis confirmed the homogenous distribution of the elements and the presence of fine fractions influencing microstructural properties. 1600°C was found to be the optimal temperature for sintering the 6YSZ – Al₂O₃ – HfO₂ ceramics.