Highly Thermal Stable Broadband Near-Infrared Luminescence in Ni<sup>2+</sup>-Doped LaAlO<sub>3</sub> with Charge Compensator
Jumpei Ueda, Tomoaki Minowa, Jian Xu, Shogo Tanaka, Takayuki Nakanishi, Takashi Takeda, Setsuhisa Tanabe
Abstract
Ni 2+ -doped LaAlO 3 perovskite ceramic samples with a charge compensator (M 4+ ) were prepared and their luminescent properties were investigated. The LaAlO 3:Ni 2+ –M 4+ (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 Ni 2+: 3 T 2 - 3 A 2 transition. The Sn 4+ -codoped one showed the highest NIR luminescence intensity. The valence state of major Ni ions is changed from Ni 3+ to Ni 2+ by codoping with Sn 4+ based on X-ray absorption spectroscopy. The LaAlO 3:Ni 2+ –Sn 4+ shows the shortest luminescence peak wavelength (λ em = 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 Ni 2+ -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 Ni 2+ 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.