Gas-sensitive resistor properties of the solid solution series Ti_x(Sn_1–ySb_y)_1–xO₂ (0<x<1, y=0, 0.01, 0.05)

Abstract

The response to carbon monoxide, methane and water vapour of gas-sensitive resistors fabricated from solid solution compounds Ti_x(Sn_1–ySb_y)_1–xO₂ where 0<x<1 and y=0, 0.01, 0.05 has been studied. For the single phase materials the variation of both conductance and conductance activation energy with composition has been explained using either a surface trap limited conductance model for undoped materials or a Schottky barrier controlled conductance for Sb-doped materials. The effect of dopant density and surface composition on the gas response has been explained using a compensated semiconductor conduction model. The surface states controlling response to water vapour are not the same as those controlling response to the combustible gases. The adsorbed oxygen states responsible for gas sensitivity lie closer to the conduction band edge for TiO₂ than for SnO₂. The surface oxygen states and surface water states are closer in energy on TiO₂ than on SnO₂. The resistivity and gas sensitivity of spinodally decomposed materials could be interpreted in terms of the phase diagram which indicated no differences from the behaviour of the single-phase components.

References

1. J. F. McAleer, P. T. Moseley, J. O. W. Norris, D. E. Williams and B. C. Tofield, J. Chem. Soc., Faraday Trans. 1, 1988, 84, 441.
2. W.-Y. Chung and D.-D. Lee, Sens. Actuators B, 1993, 13–14, 517.
3. W.-Y. Chung, D.-D. Lee and B.-K. Sohn, Thin Solid Films, 1992, 221, 304.
4. D. E. Williams, in Solid State Gas Sensors, ed. P. T. Moseley and B. C. Tofield, Adam Hilger, Bristol, 1987.
5. T. Seiyama, N. Yamazoe and H. Arai, Sens. Actuators, 1983, 4, 85.
6. Y. Shimizu, H. Arai and T. Seiyama, Sens. Actuators, 1985, 7, 11.
7. D. Garcia and D. Speidel, J. Am. Ceram. Soc., 1972, 556, 322.
8. M. Park, T. E. Mitchell and A. H. Heuer, J. Am. Ceram. Soc., 1975, 58, 43.
9. C. A. Vincent and D. C. G. Weston, J. Electrochem. Soc., 1972, 119, 515.
10. P. E. Sinclair, G. Sankar, C. R. A. Catlow, J. M. Thomas and T. Mashmeyer, J. Phys. Chem., 1997, 101, 4232.
11. V. E. Henrich and P. A. CoxThe Surface Science of Metal Oxides, Cambridge University Press, Cambridge, 1994.
12. N. N. Padurow, Naturwissenschaften, 1956, 43, 395.
13. J. W. Cahn, Acta Metall., 1961, 9, 795.
14. A. H. Schultz and V. S. Stubican, Philos. Mag., 1968, 18, 929.
15. P. K. Gupta and A. R. Cooper, Philos. Mag., 1970, 21, 611.
16. J. Takahashi, M. Kuwayama, H. Kamiya, M. Takatsu, T. Oota and I. Yamai, J. Mater. Sci., 1988, 23, 337.
17. T. C. Yuan and A. V. Virkar, J. Am. Ceram. Soc., 1986, 69, C310.
18. T. C. Yuan and A. V. Virkar, J. Am. Ceram. Soc., 1988, 71, 12.
19. D. E. Williams and P. T. Moseley, J. Mater. Chem., 1991, 1, 809.
20. G. S. Henshaw, L. J. Gellman and D. E. Williams, J. Mater. Chem., 1994, 4, 1427.
21. C. D. Wagner, in Practical Surface Analysis, 2nd edn., vol. 1 Auger and X-ray Photelectron Spectroscopy, ed. D. Briggs and M. P. Seah, Wiley, Chichester, 1990, p. 595.
22. V. Dusastre and D. E. Williams, J. Phys. Chem. B, 1998, 102, 6732.
23. D. C. Cronemeyer, Phys. Rev., 1952, 87, 876.
24. K. J. Button, D. G. Fonstad and W. Drey-Bradt, Phys. Rev. B, 1971, 4, 4539.
25. I. Manassidis, J. Goniakowski, L. N. Kantorovich and M. J. Gillan, Surf. Sci., 1995, 339, 258.
26. G. S. Henshaw, L. Morris, L. J. Gellman and D. E. Williams, J. Mater. Chem., 1996, 6, 1883.
27. N. G. Eror, J. Solid State Chem., 1981, 38, 281.
28. G. S. Henshaw, V. Dusastre and D. E. Williams, J. Mater. Chem., 1996, 6, 1351.