Synchrotron VUV-UV and positron lifetime spectroscopy study of vacancy-type defects in reactor neutron-irradiated MgO·nAl₂O₃ (n = 2)

Figures & data

Table 1. Irradiation conditions of the single crystal MgO$·$nAl${}_2$O${}_3$ (n = 2)

Irradiation facilities	Neutron flux (${\mathrm{\Phi }}_f$)(n/cm${}^2$ s)	Fluence(n/cm${}^2$)	Displacement per atom (dpa)	Atmosphere/ irradiation temperature (K)
JMTR	6.3 $\times$ 10${}^{13}$	1.2 $\times$ 10${}^{20}$	6.4 $\times$ 10${}^{-2}$	He/470
HET-20 hrs	3.9 $\times$ 10${}^{13}$	2.8 $\times$ 10${}^{18}$	1.5 $\times$ 10${}^{-3}$	He/360
HET-10 hrs	3.9 $\times$ 10${}^{13}$	1.4 $\times$ 10${}^{18}$	7.4 $\times$ 10${}^{-4}$	He/360
HET-5 hrs	3.9 $\times$ 10${}^{13}$	7.0 $\times$ 10${}^{17}$	3.7 $\times$ 10${}^{-4}$	He/360
LTL	4.8 $\times$ 10${}^{11}$	1.3 $\times$ 10${}^{17}$	6.9 $\times$ 10${}^{-5}$	He/20

Figure 1. AFM images of unirradiated (a) and fast neutron-irradiated (b) samples.

Figure 2. VUV-UV photoexcitation (left) and photoluminescence (right) spectra of irradiated and unirradiated (MgO$·$nAl${}_2$O${}_3$) (n = 2). LINAC (a), LTL(b), HET-20hrs (c), JMTR (d) and unirradiated (e).

Figure 3. Gaussian curve fitting the experimental photoexcitation spectra in the fast neutron irradiated (LTL) sample.

Figure 4. Photoexcitation spectra taken at 13 K of spinel single crystal under various irradiating conditions. LINAC (a), LTL (b), HET-20hrs (c), JMTR (d) and unirradiated (e).

Figure 5. Photoluminescence spectra of spinel single crsytal at various irradiating conditions at 13 K. LINAC (a), LTL (b), HET-20hrs (c), JMTR (d) and unirradiated (e).

Table 2. Positron lifetime parameters and trapping modes

Samples	${\mathit{\tau }}_1$(ps)	I${}_1$($\%$)	${\mathit{\tau }}_2$(ps)	I${}_2$($\%$)	Fitting variance	${\mathit{\tau }}_{av}$(ps)	${\mathit{\tau }}_b$(ps)	${\mathit{\kappa }}_d$(ns${}^{-1}$)	(${\mathit{\tau }}_2-{\mathit{\tau }}_b$)(ns)	${\mathit{\tau }}_2$/ ${\mathit{\tau }}_b$
As-recieved	189	99.2	180	0.30	1.02	189	189	$-0.00078$	$-0.009$	0.95
LTL-irradiated	178	72.6	250	25.0	1.03	197	192	0.42	0.058	1.30
HET-5 hrs-irradiated	164	61.8	230	37.1	1.04	189	184	0.65	0.046	1.25
HET-10 hrs-irradiated	160	54.7	231	44.0	1.05	192	185	0.87	0.046	1.25
JMTR-irradiated	157	58.7	237	40.7	1.00	189	182	0.91	0.055	1.30