Journal of Luminescence 39 (1988) 215—221 215 North-Holland, Amsterdam ENERGY TRANSFER BETWEEN Th 3~ AND Eu3~ IN Y 203 CRYSTALS T. KIM ANH “, T. NGOC, P. THU NGA, V.T. BICH and P. LONG institute of Physics, Academy of Sciences of Vietnam, Hanoi, Vietnam W. STR~K institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw, Poland Received 28 November 1986 Revised 20 October 1987 Accepted 29 October 1987 Energy transfer processes between Tb 3+ and Eu3± activated Y 203 crystals were investigated both by Static and kinetic analysis of luminescence. In particular the mechanism of Th —* Th and Th -. Eu energy transfer processes was investigated. The donor—donor and donor—acceptor parameters characterizing Tb —‘ Th and Th -. Eu energy transfer were determined. We have found that in the (Eu, Th, Y) 203 crystals not only Th —p Eu but also Eu -~ Th energy transfer occurs. 1. Infroduction ergy transfer was only briefly investigated by the author. The spectroscopic properties of Ln 3 + ions in In this paper we have attempted to resolve the Y 203 have been actively investigated in the last problem of energy transfer phenomena between years. This interest was prompted partially by a Th 3 + and Eu3 ± ions in Y 203. The purpose of this search of new efficient phosphors for lamp tubes investigation is to determine the different mecha- and fluorescent lamps [1]. nisms of interion interactions occurring in this The Ln 3~ ions may occupy two different sites system. In particular we will deal with a kinetic in Y 203, namely C31 and C2. The former have analysis of fluorescence quenching of Th 3 + and inversion symmetry, thus electric dipole transi- Eu3 + codoping Y 203. tions are forbidden, and the observed spectra may be attributed to the C2 symmetry sites. The crystal field analysis of Ln 3 ± ions in Y 203 was performed 2. Experimental by Leavitt et al. [2]. The radiative and multipho- non relaxations of Ln 3 + in Y 203 were investigated All measurements described in this paper were in detail by Weber [3]. performed on powder samples. The compounds The Eu 3 k-doped Y 203 is commonly applied as were prepared by firing mixtures of (Y, Eu, a red phosphor in lamp tubes. The luminescence Th)2(C204)3 at 900°C in dry air. The starting properties of Eu 3 + in Y 203 were reported long ago materials were rare earth oxides of high purity: by Forest and Ban [4] and Heber [5]. Ropp [6] Eu203 of 99.99%, Th407 of 99.99% and ‘1203 of found that codoping the (Y, Eu)203 crystals with 99.999%. Th 3 + ions leads to enhancement of Eu3 ± fluores- The spectroscopic measurements were per- cence. However, the mechanism of Th —, Eu en- formed on a spectrophotometer built in our laboratory. It consists of an SPM 2 grating mono- * Present address: Institute of Physics, Polish Academy of chromator (Carl Zeiss, Jena) and GDM 1000 grat- Sciences, Warsaw, Poland. ing monochromator (Carl Zeiss, Jena), lock-in 0022-2313/88/$03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)