Ni2+-doped LaAlO3 perovskite ceramic samples
with a charge compensator (M4+) were prepared and their
luminescent properties were investigated. The LaAlO3:Ni2+–M4+ (M = Sn, Hf, Ti, Zr) perovskites show
a broad near-infrared (NIR) luminescence peaking at around 1070 nm
with 150 nm fwhm due to the Ni2+:3T2-3A2 transition. The Sn4+-codoped
one showed the highest NIR luminescence intensity. The valence state
of major Ni ions is changed from Ni3+ to Ni2+ by codoping with Sn4+ based on X-ray absorption spectroscopy.
The LaAlO3:Ni2+–Sn4+ shows
the shortest luminescence peak wavelength (λem =
1070 nm) at 300 K due to the strong crystal field and also shows the
highest quenching temperature, T
50% of
608 K in the temperature dependence of PL intensity, due to the largest
activation energy among the Ni2+-doped NIR phosphors ever
reported. Based on the positive trend in the plot of T
50% vs PL peak energy, it is concluded that the dominant
quenching process in almost all Ni2+ phosphors is the thermally
activated crossover process. It is also demonstrated that the luminescence
peak wavelength is shifted from 1070 to 1235 nm continuously by substituting
Ga ions for the Al site.