Modification effect of Mg(OH)2–2Al(OH)3 composite gels on Y-PSZ ceramics

Abstract

A Mg(OH)2–2Al(OH)3 composite gel, synthesized via the sol-gel method, served as a modifier in the preparation of modified yttria partially stabilized zirconia (Y-PSZ) ceramics. The volume density, apparent porosity, compressive strength, thermal shock resistance, phase composition, and microstructure of the ceramics were systematically characterized. The findings reveal that, upon sintering, the Mg(OH)2–2Al(OH)3 composite gel decomposes into MgO–Al2O3 powder, which in turn in-situ generates a MgAl2O4 spinel reinforcing phase, characterized by its uniform size and distribution. The presence of this MgAl2O4 spinel applies compressive stress to the adjacent zirconia grains, effectively inhibiting their abnormal growth. By occupying the grain boundaries and establishing a mosaic structure, the compressive strength and thermal shock resistance of the Y-PSZ ceramics are significantly enhanced. Notably, an increase in the composite gel quantity correlates with a reduction in both volume density and apparent porosity of the Y-PSZ samples, whereas the compressive strength initially rises before diminishing, and the thermal shock resistance markedly improves. When the amount of Mg(OH)2–2Al(OH)3 composite gel introduced reaches 9 %, the comprehensive performance of the modified Y-PSZ ceramics is optimized. At this point, its compressive strength is increased by 1.26 times compared to the unmodified Y-PSZ ceramics, reaching 732 MPa; moreover, after undergoing 60 thermal shocks, its residual strength retention rate still remains as high as 59.15 %.