National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG-36, RO 76900, Bucharest-Magurele, Romania.
Phys Chem Chem Phys. 2012 Oct 5;14(37):12970-81. doi: 10.1039/c2cp41946g.
Pure and europium (Eu(3+)) doped ZrO(2) synthesized by an oil-in-water microemulsion reaction method were investigated by in situ and ex situ X-ray diffraction (XRD), ex situ Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), steady state and time-resolved photoluminescence (PL) spectroscopies. Based on the Raman spectra excited at three different wavelengths i.e. 488, 514 and 633 nm and measured in the spectral range of 150-4000 cm(-1) the correlation between the phonon spectra of ZrO(2) and luminescence of europium is clearly evidenced. The PL investigations span a variety of steady-state and time resolved measurements recorded either after direct excitation of the Eu(3+) f-f transitions or indirect excitation into UV charge-transfer bands. After annealing at 500 °C, the overall Eu(3+) emission is dominated by Eu(3+) located in tetragonal symmetry lattice sites with a crystal-field splitting of the (5)D(0)-(7)F(1) emission of 20 cm(-1). Annealing of ZrO(2) at 1000 °C leads to a superposition of Eu(3+) emissions from tetragonal and monoclinic lattice sites with monoclinic crystal-field splitting of 200 cm(-1) for the (5)D(0)-(7)F(1) transition. At all temperatures, a non-negligible amorphous/disordered content is also measured and determined to be of monoclinic nature. It was found that the evolutions with calcination temperature of the average PL lifetimes corresponding to europium emission in the tetragonal and monoclinic sites and the monoclinic phase content of the Eu(3+) doped ZrO(2) samples follow a similar trend. By use of specific excitation conditions, the distribution of europium on the amorphous/disordered surface or ordered/crystalline sites can be identified and related to the phase content of zirconia. The role of zirconia host as a sensitizer for the europium PL is also discussed in both tetragonal and monoclinic phases.
采用水包油微乳液反应法合成了纯氧化锆（ZrO2）和掺铕（Eu(3+)）氧化锆，并通过原位和非原位 X 射线衍射（XRD）、非原位拉曼光谱、高分辨率透射电子显微镜（HRTEM）、稳态和时间分辨光致发光（PL）光谱对其进行了研究。基于在三个不同波长（488nm、514nm 和 633nm）激发并在 150-4000cm(-1) 光谱范围内测量的拉曼光谱，清楚地证明了 ZrO2 声子谱与铕发光之间的相关性。PL 研究涵盖了各种稳态和时间分辨测量，这些测量是在直接激发 Eu(3+) f-f 跃迁或间接激发到 UV 电荷转移带之后进行的。在 500°C 退火后，Eu(3+)的整体发射主要由位于四方对称晶格位置的 Eu(3+)决定，（5）D(0)-(7)F(1)发射的晶体场分裂为 20cm(-1)。在 1000°C 下退火导致 Eu(3+)发射来自四方和单斜晶格位置的叠加，（5）D(0)-(7)F(1)跃迁的单斜晶体场分裂为 200cm(-1)。在所有温度下，还测量并确定了不可忽略的非晶/无序含量，其为单斜晶系。发现，Eu(3+)在四方和单斜位的平均 PL 寿命随煅烧温度的演化以及 Eu(3+)掺杂 ZrO2 样品中单斜相含量遵循相似的趋势。通过使用特定的激发条件，可以识别 Eu(3+)在非晶/无序表面或有序/晶相上的分布，并将其与氧化锆的相含量相关联。还讨论了氧化锆基质在四方相和单斜相中的作为 Eu(3+)PL 敏化剂的作用。
