STUDY OF SOME CERAMIC SYSTEMS BASED ON SILICIUM OXIDE

I. Coroiu1, E. Culea1, Al. Darabont2, I. Bratu3, Gh. Borodi3

1Technical University, Cluj-Napoca, Romania

2Babes-Bolyai University, Cluj-Napoca, Romania

3National Institute for Research and Development of Isotopic and Molecular Technology, 400293 Cluj-Napoca, P.O. Box 700, Romania

Introduction

Increased interest in glass-ceramics has resulted from their potential applications. In comparison with ordinary ceramics, gel-derived ceramics offer the advantage of good chemical homogeneity and purity and a better control of physical and chemical properties [1-3]. Also, gel-derived glass-ceramics can be obtained at lower temperatures.

In this paper the 0.15Gd2O3_0.85(0.95SiO20.05Na2O) gel-derived glass-ceramic and 0.95SiO20.05Na2O gel-derived ceramic heat treated at 250oC, 500oC and 1000oC were studied by means of X ray diffraction, IR spectroscopic and magnetic susceptibility measurements.

Experimental

Samples of 0.15Gd2O3_0.85(0.95SiO20.05Na2O) composition and of 0.95SiO20.05Na2O composition were prepared starting from tetraethoxysilane (99.9% purity) as source of silica, natrium peroxide and gadolinium oxide. Gd2O3 (99.99% purity) and Na2O2 (99,95% purity) were purchased from Aldrich and Merck, respectively.

The X-ray diffraction measurements were carried out on a DRON 3 diffractometer using CuK radiation. The diffraction patterns were compared to standard patterns for phase’s identification. Infrared absorption spectra were measured at room temperature (~20oC) in the range 4000-400 cm-1 with a resolution of 4 cm-1 by an infrared spectrophotometer type FT-IR Vector 25 Brucker using the KBr pellet technique. Magnetic susceptibility measurements were performed using a Weiss type magnetic balance in the temperature range 80-300 K. The accuracy of the temperature control was less than 0.1K over the whole range and the overall accuracy of the measurements of magnetic moment was less than 0.5%.

Results and discussions

The X-ray diffraction patterns of the all samples, points out that the heat-treatment has a great importance for the evolution of the crystallisation process. The presence of the gadolinium oxide in the 0.95SiO20.05Na2O matrix slows down this process.

The IR spectra of the studied samples reveal the main features characteristic of the silicate chains: a sharp absorption band at 465-473 cm-1 (bending vibrations of Si-O-Si linkages), a slightly broadened absorption band at 550-581 cm-1 (ring vibrations of six or more than six-members rings composed of [SiO4]4_ tetrahedral units) and a weak absorption band at 789-801 cm-1 (symmetric stretching vibration of [O-Si-O] bonds) which modify with respect to the heat treatment temperatures.

The magnetic susceptibility versus temperature dependence shows an antiferromagnetic behavior of the 0.15Gd2O3_0.85(0.95SiO20.05Na2O) samples.

References

1. S. Sakka, Trans. Indian Ceramic Soc., 46, 1987, p.23-37.

2. Y.Ebisawa, T.Kokubo, K.Ohura and T.Yamamuro, J.Mater.Sci.Mater.Med 4, 1992, p. 225-232.

3. Y. Lee and S. Choi, J. Am. Ceram. Soc., 79, 1996, p.992-1001.