10.1016/j.jeurceramsoc.2015.04.038
Influence of non-stoichiometry on solid-state reactive sintering of YAG transparent ceramics

Y3(1+x)Al5O12 ceramics with x changed from -4.3% to 4.7% were fabricated by a solid-state reaction method from commercial α-Al2O3 (99.98%, Alfa Aesar, Tianjin, China) and Y2O3 (99.999%, Alfa Aesar, Tianjin, China) powders. The powders were mixed in ethanol and ball-milled with high-purity corundum balls in Al2O3 jars for 10 h with 0.08 wt% MgO powder (99.998%, Alfa Aesar) and 0.8 wt% tetraethoxysilane (TEOS, >99.999%, Alfa Aesar) as sintering aids. The slurry with the solid loading of 1.8 g/ml was dried at 80 degC for 4 h in an oven and then sieved through a 200-mesh screen with the screen pore size of ~74 μm, the powder mixture was calcined at 600 degC for 4 h to remove the organic components. After that the powder mixture was uniaxially pressed into 20 mm diameter pellets and then the green bodies were compacted by cold isostatic pressing (CIP) at 250 MPa. The compacted pellets were then sintered at 1500-1750 degC under vacuum (10-3 Pa) for up to 50 h in a tungsten mesh-heated vacuum furnace. The heating rate was 5 degC/min, and the cooling rate was 10 degC/min. After sintering, the specimens were annealed at 1450 degC for 10 h in air to remove oxygen vacancies. The samples were mirror polished on both surfaces with different grade of the diamond slurries. The polished specimens were thermally etched at 1400 degC or 1500 degC for 3 h to expose the grain boundaries.
α-Al2O3
99.98%
%
Y2O3
99.999%
%
powders
ball-milled
10 h
h
MgO
99.998%
%
tetraethoxysilane (TEOS
>99.999%
%
MgO powder
0.08 wt%
wt%
tetraethoxysilane (TEOS
0.8 wt%
wt%
slurry
solid loading
1.8 g/ml
g/ml
slurry
dried
80 degC
degC
slurry
dried
4 h
h
200-mesh screen
screen pore size
~74 μm
μm
powder mixture
calcined
600 degC
degC
powder mixture
calcined
4 h
h
pellets
diameter
20 mm
mm
green bodies
cold isostatic pressing (CIP)
250 MPa
MPa
compacted pellets
sintered
1500-1750 degC
degC
compacted pellets
vacuum
10-3 Pa
Pa
compacted pellets
sintered at 1500-1750 degC under vacuum
50 h
h
heating rate
5 degC/min
degC/min
cooling rate
10 degC/min
degC/min
specimens
annealed
1450 degC
degC
specimens
annealed
10 h
h
specimens
thermally etched
1400 degC or 1500 degC
degC
specimens
thermally etched
3 h
h