Effect of Humidity Adsorption on Mixed Valence Dielectric Material LaFe1−xAlxO3. Issue 2 (20th September 2020) - Ahmed, Rida
Abstract : In mixed‐valence colossal dielectric materials, the room temperature Maxwell–Wagner response is commonly assigned, in the past literature, to the electrode effect, grain boundary effect, or internal barrier layer capacitor effect. Another underlying phenomenon is brushed aside, and that is of adsorbance of the hydroxyl ions onto the defect centers on the surface of dielectric material. The properties of dielectric materials, especially those having oxygen vacancies, are sensitive to the atmospheric moisture and easily degrade in the humid environment. To study this effect, a series of LaFe1 − x Al x O3 samples ( x = 0, 0.1, 0.2, …, 0.8, and 1) are prepared by the sol–gel method, and the effect of humidity sensitivity on their dielectric properties is seen. The samples with greater Fe concentration show distinct humidity‐sensitive properties with both metal electrodes (Pt and Ag) with a very miniscule difference in their measurement values. The effect of hydroxyl ions is further confirmed by the dielectric measurements after the thermal quenching of the samples that verify the adsorbance of water molecules on the surface of dielectric material. Abstract : The dielectric properties of LaFe1 − x Al x O3 are greatly influenced by atmospheric humidity because of the presence of multivalent Fe ions. The relative humidity measurements performed with Pt and Ag coated pellets show no remarkable change in the %RH values, showing that the bulk material plays a significant role toward humidity sensitivity, irrespective of the type of electrode.