516
H. Klym et al.
changes in pore-related water-sorption processes. The increase of humidity sensitivity in ceramics sintered at 1300 ◦ C is related to the fact that close to optimal
pore size distribution is achieved. It is shown that in all sintered samples there are
pores with radii larger than 10–20 nm, which do not participate in the processes of
capillary condensation, although their presence is needed to support fast response
of humidity-sensitive elements to the change of relative humidity. Positrons are
trapped more strongly in the spinel-type ceramics obtained at lower temperature,
and this is reflected in the second component of lifetime spectra. The third and the
fourth longest components in the resolved lifetime spectra are due to “pick-off”
annihilation of o-Ps atoms in the intergranular pores. The observed o-Ps lifetimes
are related to the nanopores with radius of ∼0.3 and ∼1.3÷1.5 nm based on classic
Tao-Eldrup equation. The reported data were confirmed by Hg-porosimetry and
SEM results.
Acknowledgment H. Klym thanks the Ministry of Education and Science of Ukraine for its
support (grant no. 0116 U004411).
References
1. Zhi C, Chi L (2005) Humidity sensors: a review of materials and mechanisms. Sens Lett
3(4):274–295. https://doi.org/10.1166/sl.2005.045
2. Kulwicki BM (1991) Humidity sensors. J Am Ceram Soc 74(4):697–708.
https://doi.org/10.1111/j.1151-2916.1991.tb06911.x
3. Li Y, Fu ZY, Su BL (2012) Hierarchically structured porous materials for energy conversion
and storage. Adv Funct Mater 22(22):4634–4667. https://doi.org/10.1002/adfm.201200591
4. Gusmano G, Montesperelli G, Traversa E (1993) Microstructure and electrical properties of MgAl 2 O 4 thin film for humidity sensors. J Am Ceram Soc 76:743–750.
https://doi.org/10.1111/j.1151-2916.1993.tb03669.x
5. Farahani H, Wagiran R, Hamidon MN (2014) Humidity sensors principle, mechanism, and fabrication technologies: a comprehensive review. Sensors 14(5):7881–7939.
https://doi.org/10.3390/s140507881
6. Asami K, Mitani S, Fujimori H, Ohnuma S, Masumoto T (1999) Characterization of Co-Al-O
magnetic thin films by combined use of XPS. XRD and EPMA Surf Interface Anal 28:250–
253. https://doi.org/10.1002/(SICI)1096-9918(199908)28:1<250::AID-SIA587>3.0.CO;2-T
7. Asami K, Ohnuma T (1998) Masumoto XPS and X-ray diffraction characterization of thin CoAl-N alloy films prepared by reactive sputtering deposition. Surf Interface Anal 26:659–666.
https://doi.org/10.1002/(SICI)1096-9918(199808)26:9<659::AID-SIA412>3.0.CO;2-Z
8. Krause-Rehberg R, Leipner HS (1999) Positron annihilation in semiconductors. In: Defect
studies. Springer, Berlin/Heidelberg/New York, p 378
9. Shpotyuk O, Filipecki J (2003) Free volume in vitreous chalcogenide semiconductors: possibilities of positron annihilation lifetime study. Wyd-wo WSP w Czestochowie, Czestochowa
10. Hübner C, Staab T, Krause-Rehberg R (1995) On the interpretation of positronannihilation data in powders and fine-grained materials. Appl Phys A 61(2):203–206.
https://doi.org/10.1007/BF01538390
11. Weaver PM, Cain MG, Stewart M, Anson A, Franks J, Lipscomb IP, McBride JP, Zheng D,
Swingler J (2012) The effects of porosity, electrode and barrier materials on the conductivity
of piezoelectric ceramics in high humidity and dc electric field smart materials and structures.
Smart Mater Struct 21(4):045012. https://doi.org/10.1088/0964-1726/21/4/045012
H. Klym et al.
changes in pore-related water-sorption processes. The increase of humidity sensitivity in ceramics sintered at 1300 ◦ C is related to the fact that close to optimal
pore size distribution is achieved. It is shown that in all sintered samples there are
pores with radii larger than 10–20 nm, which do not participate in the processes of
capillary condensation, although their presence is needed to support fast response
of humidity-sensitive elements to the change of relative humidity. Positrons are
trapped more strongly in the spinel-type ceramics obtained at lower temperature,
and this is reflected in the second component of lifetime spectra. The third and the
fourth longest components in the resolved lifetime spectra are due to “pick-off”
annihilation of o-Ps atoms in the intergranular pores. The observed o-Ps lifetimes
are related to the nanopores with radius of ∼0.3 and ∼1.3÷1.5 nm based on classic
Tao-Eldrup equation. The reported data were confirmed by Hg-porosimetry and
SEM results.
Acknowledgment H. Klym thanks the Ministry of Education and Science of Ukraine for its
support (grant no. 0116 U004411).
References
1. Zhi C, Chi L (2005) Humidity sensors: a review of materials and mechanisms. Sens Lett
3(4):274–295. https://doi.org/10.1166/sl.2005.045
2. Kulwicki BM (1991) Humidity sensors. J Am Ceram Soc 74(4):697–708.
https://doi.org/10.1111/j.1151-2916.1991.tb06911.x
3. Li Y, Fu ZY, Su BL (2012) Hierarchically structured porous materials for energy conversion
and storage. Adv Funct Mater 22(22):4634–4667. https://doi.org/10.1002/adfm.201200591
4. Gusmano G, Montesperelli G, Traversa E (1993) Microstructure and electrical properties of MgAl 2 O 4 thin film for humidity sensors. J Am Ceram Soc 76:743–750.
https://doi.org/10.1111/j.1151-2916.1993.tb03669.x
5. Farahani H, Wagiran R, Hamidon MN (2014) Humidity sensors principle, mechanism, and fabrication technologies: a comprehensive review. Sensors 14(5):7881–7939.
https://doi.org/10.3390/s140507881
6. Asami K, Mitani S, Fujimori H, Ohnuma S, Masumoto T (1999) Characterization of Co-Al-O
magnetic thin films by combined use of XPS. XRD and EPMA Surf Interface Anal 28:250–
253. https://doi.org/10.1002/(SICI)1096-9918(199908)28:1<250::AID-SIA587>3.0.CO;2-T
7. Asami K, Ohnuma T (1998) Masumoto XPS and X-ray diffraction characterization of thin CoAl-N alloy films prepared by reactive sputtering deposition. Surf Interface Anal 26:659–666.
https://doi.org/10.1002/(SICI)1096-9918(199808)26:9<659::AID-SIA412>3.0.CO;2-Z
8. Krause-Rehberg R, Leipner HS (1999) Positron annihilation in semiconductors. In: Defect
studies. Springer, Berlin/Heidelberg/New York, p 378
9. Shpotyuk O, Filipecki J (2003) Free volume in vitreous chalcogenide semiconductors: possibilities of positron annihilation lifetime study. Wyd-wo WSP w Czestochowie, Czestochowa
10. Hübner C, Staab T, Krause-Rehberg R (1995) On the interpretation of positronannihilation data in powders and fine-grained materials. Appl Phys A 61(2):203–206.
https://doi.org/10.1007/BF01538390
11. Weaver PM, Cain MG, Stewart M, Anson A, Franks J, Lipscomb IP, McBride JP, Zheng D,
Swingler J (2012) The effects of porosity, electrode and barrier materials on the conductivity
of piezoelectric ceramics in high humidity and dc electric field smart materials and structures.
Smart Mater Struct 21(4):045012. https://doi.org/10.1088/0964-1726/21/4/045012