The humidity sensing properties and mechanism of strontium-hexaferrite ceramics

TL;DR

This study investigates the humidity sensing properties of strontium-hexaferrite ceramics, analyzing their conduction mechanisms and proposing an impedance model to explain their response to water vapor at room temperature.

Contribution

It provides new insights into the humidity sensing mechanism of X-type and Z-type strontium-hexaferrite ceramics, including the role of oxide vacancies and water interactions.

Findings

Impedance spectra model explains humidity response

Electronic and protonic conduction mechanisms identified

Surface reactions with water influence sensing behavior

Abstract

The humidity sensitivity of n-type strontium-hexaferrite semiconductors, X-type (Sr2Co2Fe28O46) and Z-type (Sr3Co2Fe24O41), are investigated at room temperature. The contact and reactions between water and material surface are demonstrated considering the formation of oxide ion vacancy, singly-ionized / fully-ionized oxide ion vacancy, and the chemisorbed / physisorbed / condensed water. An impedance spectra model is proposed considering the material-electrode interface, interior material, grain boundary, absorbed water and Warburg response. The mechanism of electronic coupled with protonic conduction and humidity sensing mechanism are explained.