JOURNAL OF MATERIALS SCIENCE 28(t993) 4435-4441 Si02-Sm203 vitreous films via the sol.el method M. ZAHARESCU, C. PIRLOG, M. GARTNER Institute of Physical Chemistry, Splaiul Independentei 202, Bucharest 79611, Romania F. MOISE ZECASIN-SA, Splaiul Independentei 202, Bucharest 79611, Romania V. TEODORESCU Institute of Physics and Technology of Materials, Bucharest - Magurele, P.O. Box MG- 7, Bucharest 76900, Romania Si02-Sm203 vitreous films 1 20 nm thick were obtained via the sol-gel method. Infrared, energy-dispersive analysis of X-rays, spectroscopic ellipsometry and absorption spectroscopy showed a total inclusion of samarium in the silica matrix, which remains amorphous up to 1000 ~ The inclusion of the samarium ion increases the porosity. The optical properties of films were investigated by spectro-ellipsometry, and the parameters obtained were compared with those obtained by other techniques. 1. Introduction The preparation of glass coatings is one of the most important fields of application of the sol-gel technique and many compositions have been produced to en- hance some properties or to give new ones to different substrates [1]. An important feature of sol-gel coat- ings is the ability to control the refractive index through variations of the sol; for example, by pre- aggregating the sol, a porous film with a low index results [2]. Silica films are electrically conducting and infrared- reflecting coatings with a wide range of applications. In the last few years, growing interest has been shown in the production ofcoloured thin films based on SiO 2 doped with transition metal ions [3-143. In this paper we present results concerning the preparation and characterization of vitreous SiO2, containing Sm203. To our knowledge, vitreous coatings obtained via the sol gel method for this system have not been reported in the literature. 2. Experimental procedure The compositions of the initial solutions and the experimental conditions are presented in Table I. Ethylorthosilicate (Serva) was used as the SiO2 source, Sm(NO3)3-H20 (Merck) was the Sm20 3 source, and absolute ethylic and methylic alcohol p.a. (Reactivul) were used as solvents and nitric acid p.a. (Reactivul) as the catalyst. The pH of the initial solution was 6, but in order to maintain the solution viscosity at a low value, the pH was adjusted to 1. The viscosity of the solution before deposition was 1.08 cP. Thin films were obtained by dip-coating on com- mon glass (silica-soda-lime) previously cleaned. Usually, both faces of the substrate were coated. The withdrawal speed was typically 5 cm rain ~. After each coating procedure, the films were dried and thermally treated to 500~ in order to densify them. The solutions and the films obtained from them were characterized as follows. The viscosity of solu- tions prior to deposition was determined by means of a H6ppler viscometer. Differential thermal analysis was carried out using a MOM-OD-103 derivato- graph, and infrared spectroscopy was performed on a Carl Zeiss Jena Specord 75 IR Spectrophotometer. X- TAB L E I Solution compositions and experimental conditions Sample $1 $2 $3 $4 $5 C2HsOH 1.31 1.31 1.31 1.31 1.31 Si(OC2H5)4 CH3OH 11.47 I 1.47 11.47 11.47 l 1.47 Si(OC2Hs)~ H20 5.25 5.25 5.25 5.25 5.25 Si(OC2H5)4 Sm(NO3)~ 9 6H20 0.1 0.1 0.I 0.1 0.1 Si(OC2H5)4 pH 1 1 t 1 1 Immersion time 5 5 5 3 1 (rain) Temp. of thermal treatment 500 500 500 500 500 (oc) Time of thermal treatment 30 30 30 30 30 (rain) 0022-2461 9 1993 Chapman & Hall 4435