Humidity-Dependent Dielectric and Electrical Behavior of Strontium Iron Vanadate Ceramics

Abstract

Metal-oxide ceramics with perovskite-related structures offer tunable properties for sensing applications. The strontium iron vanadate ceramic system remains underexplored for humidity sensing despite theoretical interest in Sr2FeVO6-type compositions. This study presents sol-gel synthesis of strontium iron vanadate ceramic at 900°C and its characterization as an impedance-type humidity sensor. XRD revealed a multi-phase composition with a perovskite-related Ia-3d superstructure (a = 10.040 Å, 20 superstructure reflections systematically absent in Pm-3m) and Sr-vanadate phases. FTIR confirmed a hydrophilic metal-oxygen framework with BO6 octahedral vibrations characteristic of perovskite-related structures. SEM showed ~1.6 μm grains with inter-particle porosity; DLS showed ~460 nm agglomerates. Zeta potential was −15 mV, indicating surface hydroxylation. Impedance spectroscopy (50 Hz–5 MHz, 11–97% RH) demonstrated 621%/%RH sensitivity at 50 Hz with two clearly separated conduction regimes: localized hopping mechanisms dominating at low RH and long-range proton transport occurring through continuous water pathways at elevated RH. The dielectric permittivity increased to approximately 106–107 at low frequencies, accompanied by a more conduction-related loss behavior at higher humidity, while the AC conductivity rose by nearly four orders of magnitude. This work reports humidity sensing properties of sol-gel-derived strontium iron vanadate ceramic with perovskite-related contributions and provides mechanistic insight into two-stage conduction behavior.