The luminescence of tin dioxide activated by europium was first studied by Grabtree [1–3] and later by Matsuoka and co-workers [4, 5] and Blasse and Van Keulen [6]. As has been pointed out [5], SnO2:Eu is of interest as a luminescent system, in which emission can be excited by low energy electrons. Recently, Kynev et al. [7] using the oxide or hydroxide of Sn(II) as precursor, have achieved a considerable luminescence efficiency under the 254 nm mercury line excitation at relatively low preparation temperatures of the luminophore (800– 1000 8C). This paper presents the results of the authors’ further investigation and aims to clarify: (i) how the factors determining the rate of oxidation of SnO to SnO2 influence the luminescence of SnO2:Eu as well as (ii) whether thermal treatment preceding the oxidation of SnO changes the emission of SnO2:Eu. The authors preliminary data on the rate dependence of oxidation on the luminescence are presented in [8]. The sample preparations were carried out in an apparatus, which allows switching of the flow from an inert gas (argon) to the flow of an oxidizer gas (air or oxygen) in the course of the thermal treatment. Thus control of the composition of the gas atmosphere and isothermality of the oxidation process are achieved. Tin(II) oxide product (Carlo Erba) or prepared from SnCl2 and Na2CO3 was used as the precursor. The activator (1 mol %) was introduced by impregnation of SnO with an aqueous solution of Eu(NO3)3 and drying at 100 8C. The sample preparation conditions and the intensity of their f–f emission measured at 254 nm excitation are presented in Table I (Imax is the integral intensity of the three f–f bands in the spectral region 585–605 nm). The results show a very pronounced influence of the rate of oxidation on the luminescence yield. Comparing the Imax values of samples 1, 2 and 3, prepared at the same temperature of activation (ta), but at different rates of oxidation, it can be seen that the emission increased strongly with increasing rate of the oxidation process. Sample 1 is characterized by the highest value of Imax. In that case oxidation is realized at 900 8C, since the tin(II) oxide impregnated by Eu(NO3)3 is carried into the furnace in the argon flow and the argon to air flow switching is performed 5 min later. In contrast, the sample 2, obtained by a slow temperature ramp from 25 to 900 8C in flowing air and with a further temperature hold at 900 8C for 60 min, exhibits the lowest intensity. Sample 3 is activated similarly to sample 1 using a fast heating rate, but in the presence of air flow at the beginning of the thermal treatment. Under these conditions a large part of the SnO is oxidized before its temperature achieves 900 8C.