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Properties of Modified Anodic‐Spark‐Deposited Alumina Porous Ceramic Films as Humidity Sensors
Author(s) -
Chen Zhi,
Jin MaoChang,
Zhen Chao,
Chen GuanHua
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb04106.x
Subject(s) - materials science , porosity , sulfuric acid , humidity , chemical engineering , barrier layer , anode , aqueous solution , dew point , ceramic , composite material , layer (electronics) , metallurgy , chemistry , electrode , organic chemistry , physics , meteorology , engineering , thermodynamics
α‐Alumina films formed by anodic spark deposition in the melt of NaHSO 4 ‐KHSO 4 mixture (200°C) exhibited a porous structure. It has been found that the porosity and amount of α‐phase varied with anodic current density. By electrical measurements, films were found to exhibit a continuous open‐pore structure, causing failure of humidity sensors. This problem can be overcome by reanodization of the anodicspark‐deposited alumina films in either borax aqueous solution or sulfuric acid solution for a short time to form an effective barrier layer at the pore base. The modified anodic‐spark‐deposited alumina films showed highly sensitive response to water vapor change in the range of −76° to +20°C dew point with much improved long‐term stability. The humidity characteristics of the α‐alumina films were qualitatively explained in terms of the BET theory and condensation theory.