Contact Electrification in Inorganic Binary Compounds

Abstract

The amount of electric charge induced on a sample powder surface by contact with another reference powder has been measured by using a blow‐off method. Samples are three binary inorganic compound systems, consisting of 36 oxides, 15 fluorides, or 13 sulfides of various metal elements. Though the blow‐off charge depends considerably on particle size, charging tendency observed among samples is essentially unvaried even when they contact with different reference materials. Therefore, a series of materials, arranged according to the magnitude of values, is governed by their chemical compositions, and can be adopted as a quantitative contact electrification series. The value for each system is found to shift linearly to a negative direction with an increase in the generalized electronegativity for constituent metal cations. This is understood in terms of the acid‐base properties either in an aqueous or in a gaseous phase, which are correlated with . The charging tendency is also affected by anions, and shifts toward the negative direction in the order of oxides, fluorides, and sulfides. This order agrees with their acid strength order in a gaseous phase, but not with that in an aqueous phase. Extension of the results to more general systems, including materials with more complex chemical compositions, is discussed.