Spectrochimica Acta Part A 60 (2004) 89–95 Photoluminescence and Raman studies of Sm 3+ and Nd 3+ ions in zirconia matrices: example of energy transfer and host–guest interactions Zerihun Assefa a,∗ , R.G. Haire a , P.E. Raison b,1 a Oak Ridge National Laboratory, Chemical Sciences Division, MS 6375, Oak Ridge, TN 37831-6375, USA b European Commission-Institute for Energy, Joint Research Center of Petten, Postbus Nr. 2 1755 ZG Petten, The Netherlands Received 4 March 2003; accepted 31 March 2003 Abstract Photoluminescence and Raman studies on Sm 3+ - and Nd 3+ -doped zirconia are reported. The Raman studies indicate that the monoclinic (m) phase dominates up to a 10 at.% lanthanide level, while stabilization of the cubic phase is attained at ∼20 and ∼25 at.% of Sm 3+ and Nd 3+ , respectively. Both systems are strongly luminescent under photo-excitation. The emission spectrum at 77 K of the ZrO 2 :Sm 3+ system consists of a broad band at 505 nm, that corresponds to the zirconia matrix. At room temperature the band maximum blue-shifts to 490 nm. Sharper bands corresponding to f–f transitions within the Sm 3+ ion are also exhibited in the longer wavelength region of the spectrum. Exclusive excitation of the zirconia matrix provides sensitized emission from the acceptor Sm 3+ ion. The excitation profile is dominated by a broad band at 325 nm when monitored either at the zirconia or at one of the Sm 3+ emissions. A spectral overlap between the 6 H 5/2 → 4 G 7/2 absorption of the Sm 3+ ion with the zirconia emission leads to an efficient energy transfer process in the systems. Multiple facets of the spectral behavior of the Sm 3+ or Nd 3+ in the zirconia matrices, as well as the effects of compositions on the emission and Raman properties of the materials, and the role of defect centers in photoluminescence and the energy transfer processes are discussed. Published by Elsevier B.V. Keywords: Photo-luminescence; Energy-transfer; Lanthanide; Sensitized emission 1. Introduction Zirconia-based oxide ceramics are attractive for a vari- ety of applications, such as fuel cells, oxygen sensors, re- fractory materials, and optical transparency [1–4]. Several attributes influence the physical and chemical properties of these materials, which include crystal structures, type and level of dopant, as well as the temperature [4]. Pure ZrO 2 exists in three polymorphic phases (monoclinic, tetrago- nal or cubic), with the more symmetrical phases being ob- tained with increasing temperatures. Doping zirconia with different cations [5] can stabilize the cubic and tetragonal phases at lower or even ambient temperatures. This stabi- lization improves important mechanical and electrical prop- ∗ Corresponding author. Tel.: +1-865-754-5013; fax: +1-865-574 4987. E-mail address: assefaz@ornl.gov (Z. Assefa). 1 On leave from the Commissariat ` a l’Energie Atomique, CEA-Cadarache DEN/DEC/SPUA/ LMPC 13108, France. erties of ZrO 2 . In this regard, lanthanide dopants in zirco- nia are known to stabilize the higher symmetry tetragonal and/or cubic phases [6–8] over a temperature range pertinent to catalytic reactions. Various metal ions incorporated into zirconia materials can achieve special optical properties. Placing f-electron elements in zirconia-based materials has the potential for solid-state photonic device applications [9]. The ability to stabilize each crystalline phase of zirconia at ambient tem- perature provides an opportunity for correlating the optical properties with the structure. In addition, structural modi- fications may impact the electronic structure of the lattice, and useful chemical and optical properties could emerge. As the main structural difference between these zirconia phases is due to displacements of the oxygen atoms in the lattices, it is of interest to follow the spectroscopic consequences ac- company the structural modifications. Most of the luminescence work conducted on zirconia based materials to date has involved the cubic and/or tetrag- onal structures [10]. A number of cubic stabilized ZrO 2 ma- 1386-1425/$ – see front matter. Published by Elsevier B.V. doi:10.1016/S1386-1425(03)00183-5