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Zirconium titanate ceramics for humidity sensors synthesized by mechanochemical treatment and sintering

Recently it has been reported that the ZrTiO4 (ZT) ceramic can possess humidity sensing ability. The sensitivity and stability of sensing are related to the porous structure of the ceramics. In this work the correlation of ZT ceramic structure at the nano-scale to the electric response in different atmospheres was investigated. High-energy ball milling is used for mechanochemical treatment of TiO2 and ZrO2, thus facilitates the solid state reaction toward ZrTiO4 even before heat treatment. Prior to sintering the ball milled powder precursor was compacted at 180 MPa. The ceramics were prepared by sintering for 8 h at 1100, 1200, 1300 and 1400 °C. The solid state reaction was completed after sintering at 1200, 1300 and 1400 °C as observed by Raman spectroscopy and XRD, while sample sintered at 1100 °C contained only 41.03 wt.% of ZrTiO4. Scanning electron microscopy showed homogenous porous material, with lower porosity and larger sintered grains after higher temperatures. HRTEM indicated that the ceramics sintered at the lower temperature (1100 and 1200 °C) formed polycrystalline sintered grains, while at higher temperatures the grains become single crystals. Highly porous ZT ceramics showed significant difference in electrical conductivity measured in nitrogen and in air, indicating promising application as humidity sensors. On the other hand, the sample sintered at 1400 °C did not show any difference in electrical response depending on the atmosphere due to low porosity of ceramics. The influence of the nanostructure to the electrical properties of the ZT ceramics will be discussed.

ZrTiO4 ceramics; humidity sensors; mechanochemical treatment; sintering

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