Development and characterization of 3Y-TZP/SrAl12O19 ceramic composites: a threshold between densification and toughening

abstract

Alumina-toughened zirconia (ATZ) composites combine the high fracture toughness and bending strength of zirconia with alumina's high hardness and wear-resistance. Usually, ATZ composites are based on equiaxial alumina grains. However, the use of Al2O3 reinforcement phases containing high aspect ratio can impair better mechanical properties. In this work, ceramic matrices based on yttria-stabilized tetragonal zirconia (3Y-TZP) were reinforced with different concentrations of in-situ growth strontium hexaluminate (Sr-H6A), an aluminabased compound with platelet-like crystallographic habit. The Sr-H6A powder was synthesized by sol-gel route, which resulted in an amorphous equiaxial precursor powder (D50 ti 370 nm). The composites were prepared by a wet route, considering different concentrations of reinforcement phase (0, 5, 10, 15, and 20 wt%). The samples were processed by uniaxially pressing and sintered at 1500 degrees C, 1550 degrees C or 1600 degrees C under isothermal holding time of 2 h. The synthesized powders reacted in-situ, resulting in monophasic Sr-H6A crystals with platelet-like shape of high aspect ratio (ti6:1). The sintered composites presented tetragonal zirconia (T-ZrO2) as major crystalline phase with secondary phases of a distorted tetragonal zirconia phase (T '-ZrO2) and Sr-H6A. However, by increasing the Sr-H6A reinforcement phase concentration, the densification of the composites is hindered, with the best densification being found at 1600 degrees C for the composite reinforced with 5 wt% of Sr-H6A (98.5 %). The mentioned group presented good bending strength (sigma 0 ti 920 MPa) and improved fracture toughness (KIF ti 9.7 f 0.3 MPa m0.5) when compared with the control group (sigma 0 ti 1000 MPa and KIF ti 6.9 f 0.2 MPa m0.5). Evidence of toughening mechanisms, e.g., crack-bridging and crack-deflection, could be related to the presence of Sr-H6A crystals of high aspect ratio.

keywords

LANTHANUM HEXAALUMINATE; MECHANICAL-PROPERTIES; FRACTURE-TOUGHNESS; ALUMINA; MICROSTRUCTURE; ZTA; STRONTIUM; SRAL2O4; AL2O3

subject category

Materials Science

authors

Alves, MFRP; Silva, MRF; dos Santos, C; Gouveia, S; Ferreira, P; Olhero, S

Groups

G2 - Photonic, Electronic and Magnetic Materials
G5 - Biomimetic, Biological and Living Materials

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

M.F.R.P. Alves acknowledges the FCT for the PhD grant 2021.06615.BD. M.R.F. Silva acknowledges the FCT for the PhD grant SFRH/BD/145661/2019. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020) , UIDP/50011/2020 (DOI 10.544 99/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) and IEETA ( www.ieeta.pt) , UIDB/00127/202 (DOI 10.54499/UIDB/00127/2020 & UIDP/00127/2020 (DOI 10.54499/UIDP/00127/2020) , financed by national funds through the FCT/MCTES (PIDDAC) . C. Santos acknowledges the FAPERJ for the grants, E26-201.476/2014 and E26-202.997/2017, and CNPq for the grant 311119/2017-4.