[01] R. Alvarez Roca, LIEC, Chemistry Deparment, Federal University of São Carlos, São Carlos-SP, Brazil. [02] F. Guerrero Zayas, Physics Department, ICE, Federal University of Amazonas, Manaus-AM, Brazil.

The influence of Li₂O and humidity on structural and electrical properties of TiO₂ ceramics are presented for two different concentrations (0.02 and 0.06 mol%). The X-Ray analysis shows a single phase compound for 0.02, due to the Li incorporation into the rutile, while the pattern for the 0.06 composition shows two phases. The structural effects are corroborated by Infrared Spectroscopy where the vibrational modes are discussed for each composition. The electrical behavior is also shown at room temperature and for each composition using a.c. measurement. The effect of Li₂O addition on water adsorption mechanism as well as the humidity sensibility is analyzed. An equivalent circuit, from impedance spectroscopy, is proposed and the physical processes that take place inside the ceramic are described.

TiO₂, Humidity, Electrical Properties

[01] Yamazoe, N., Simizu, Y., (1986). Humidity sensors: principles and applications. Sens. Actuators, 10: 379–398. [02] Kulwicki, B.M., (1991). Humidity sensors. J. Am. Ceram. Soc., 74 (4) 697–708. [03] Traversa, E. (1995). Ceramic sensors for humidity detection: the state of-the-art and future developments. Sens. Actuators B, 23: 135–156. [04] Chen, Z. and Lu, C. (2005). Humidity Sensors: A Review of Materials and Mechanisms. Sensor Lett., 3: 274-295. [05] Carpenter, M. A., Mathur, S. and Kolmakov, A. (Eds.), (2013). Metal Oxide Nanomaterials for Chemical Sensors, Springer, NY. [06] Farahani, H., Wagiran, R. and Hamidon, M. N. (2014). Humidity Sensors Principle, Mechanism, and Fabrication Technologies: A Comprehensive Review. Sensors, 14: 7881-7939. [07] Katayama, K., Hasegawa, K., Takahashi, Y., Akiba, T., Yanagida, H. (1990). Humidity Sensitivity of Nb2O5-Doped TiO₂ Ceramics. Sens. Actuators A Phys., 24: 55–60. [08] Yeh, Y. Ch., Tseng, T.Y. and Chang, D. (1990). Electrical Properties of TiO₂-K₂Ti₆O₁₃ Porous Ceramic Humidity Sensor. J. Am. Ceram. Soc. 73: 1992-1998. [09] Jain, M.K., Bhatnagar, M.C., Sharma, G.L. (1999). Effect of Li doping on ZrO₂–TiO₂ humidity sensor, Sens. Actuators B 55: 180–185. [10] Ying, J., Wan, C., He, P. (2000). Sol-Gel Processed TiO₂-K₂O-LiZnVO₄ Ceramic Thin Films as Innovative Humidity Sensors. Sens. Actuators B Chem. 62: 165–170. [11] Zaleska, A. (2008). Doped-TiO₂: A Review, Recent Patents Eng., 2: 157-164. [12] Anbia, M., and Fard, S.E.M. (2011). Improving Humidity Sensing Properties of Nanoporous TiO₂-10 mol% SnO₂ Thin Film by Co-Doping with La³⁺ and K⁺. Sens. Actuators B Chem., 160: 215-221. [13] Golonka, L.J., Licznerski, B. W., Nitsch, K. and Teterycs H. (1997). Thick-film humidity sensors, Meas. Sci. Technol. 8:92-98. [14] Suresh, A. M. E., Magdalane, C. M. and Nagaraja, K S. (2002). Zinc(II) Oxide–Yttrium(III) Oxide Composite Humidity Sensor Phys. Stat. Sol. (a) 191: 230-234. [15] Geng, W., Wang, R.; Li, X., Zou, Y., Zhang, T., Tu, J., He, Y., and Li, N. (2007). Humidity Sensitive Property of Li-Doped Mesoporous Silica SBA-15. Sens. Actuators B Chem., 127: 323–329. [16] Montesperelli, G., Pumo, A., Traversa, E., Bearzotti, A., Montenero, A., and Gnappi, G. (1995). Sol-Gel Processed TiO2-Based Thin Films as Innovative Humidity Sensors. Sens. Actuators B Chem., 25: 705–709. [17] Garcia-Belmonte, G., Kytin, V., Dittrich, T. and Bisquert, J. (2003). Effect of humidity on the ac conductivity of nanoporous TiO₂, J Appl. Phys., 94: 5261-5264. [18] Wang, Z., Shi, L., Wu, F., Yuan, S., Zhao, Y. and Zhang, M. (2011). The sol–gel template synthesis of porous TiO₂ for a high performance humidity sensor, Nanotechnology, 22: 275502. [19] Alvarez Roca, R., Guerrero, F., Eiras, J. A. and Guerra, J.D.S. (2015). Structural and electrical properties of Li-doped TiO₂ rutile ceramics, Ceram. Int., 41: 6281–6285. [20] Alvarez Roca, R., Guerrero, F., Garcia-Belmonte, G. and Bisquert, J. (2002). Study of the humidity effect in the electrical response of the KSbMoO₆ ionic conductive ceramic at low temperature, J. Mater. Sci. Eng., B 90: 291-295. [21] Faia, P.M., Ferreira, A.J., and Furtado, C.S. (2009). Establishing and Interpreting an Electrical Circuit Representing a TiO₂-WO₃ Series of Humidity Thick Film Sensors. Sens. Actuators B Chem., 140: 128–133. [22] Koudriachova, M. V., Harrison, N. M. and de Leeuw, S. W. (2002) Density-functional simulations of lithium intercalation in rutile. Phys. Rev., B 65: 235423. [23] Burdett, J. K., Hunghbanks, T., Miller, G. J., Richardson, J. W. and Smith, J. V. (1987). Structural-electronic relationships in inorganic solids: powder neutron diffraction studies of the rutile and anatase polymorphs of titanium dioxide at 15 and 295 K, J. Am. Chem. Soc., 109: 3639-3646. [24] van Hassel, B. A., Boukam, B. A. and Burggraaf, A. J. (1992). Oxygen transfer properties of ion-implanted yttria-stabilized zirconia Solid. State Ionic 53-56: 890-903.