engleski

X-ray powder diffraction study of SnO2 doped with antimony

Tin oxide, SnO2 , has been widely used as a conductor in electronic devices. Dopands, such as antimony (Sb), incorporated into SnO2 thin films cause the change in resistivity of such films. The resistivity decreases for lightly-doped SnO2, and increases for havily-doped SnO2 (A. Rohatgi et al., J. Am. Ceram. Soc. 57 (1974) 278(. The mechanism of this phenomenon is not well understood yet. The aim of the present work is to examine the influence of Sb dopand on the structure of SnO2. The samples of pure SnO2 and ones doped with 2.93 and 5.90 at% Sb were hydrothermally prepared at 250 oC and pressure of 2.5 MPa. Powdered samples were examined by X-ray diffraction using a vertical goniometer and monochromatized Cu K( radiation. Two data sets were collected for each sample, one of the pure sample and the other of the sample containing Si powder as internal standard. All patterns were analyzed by the powder-pattern-fitting methods (H. Toraya, J. Appl. Cryst. 19 (1986) 440(, and the Rietveld method using the program PFLS (H. Toraya and F. Marumo, Rep. Res. Lab. Eng. Mater. Tokyo Inst. Technol. 5 (1980) 55( was performed for pure SnO2 and for the sample doped with 5.9 at% Sb. The samples are tetragonal, space group P42/mnm. Refined unit-cell parameters are: SnO2: a=4.7331(11), c=3.1815(9) A, Rwp=0.142, SnO2 doped with 2.93 at% Sb: a=4.7399(5), c=3.1854(4) A, Rwp=0.084, SnO2 doped with 5.90 at% Sb: a=4.7402(5), c=3.1856(4) A, Rwp=0.092. Diffraction lines were broadened, indicating the nanosized crystallites in the samples. The lines of pure SnO2 showed the greatest broadening. As the amount of dopand increased the broadening decreased. Also, the lines hk0 were systematically broader than the lines hk1, hk2 and hk3 for all samples. Rietveld refinement for pure SnO2 confirmed the rutile-type structure: Sn4+ on 2(a) sites (0,0,0; 1/2,1/2,1/2) and O2- on 4(f) sites, +(x,x,0; 1/2+x,1/2-x, 1/2), with x=0.307, as reported for single crystal (W.H. Baur, Acta Cryst. A 9 (1956) 515(. In the case of the sample doped with 5.90 at% Sb the Sb3+ ion is substituted on the Sn4+ sites in the SnO2 lattice changing x to 0.3076.

Tin oxide. thin films. XRD.Rietveld refinement

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