Frequency-Dependent Dielectric and Electrical Characterization of Some Wood Species under Different Conditions: Correlation of Permittivity, Loss Factor, Conductivity, and Impedance

Abstract

Dielectric properties of tree samples belonging to Anatolian chestnut, sessile oak, and Scots pine species were measured in the frequency range of 100 Hz to 1 MHz. Test samples were subjected to three different surface conditions, namely control (CW), two-week water-soaked (SW), and two-coat varnish application (VW). The test samples were characterized by analyzing capacitance (C), dielectric properties (ε′, ε″, and tanδ), AC electrical conductivity (σ_ac), normalized conductance (G/ω), and impedance components (Z′ and Z″). Frequency analysis revealed that the SW samples exhibited higher C, ε′, ε″, tanδ, and σ_ac values, whereas the VW samples maintained low and stable dielectric properties because of the insulating effect of the varnish layer. The σ_ac values reached approximately 10⁻³ S cm⁻¹ in the SW samples but remained around 10⁻⁷ S cm⁻¹ in the CW and VW samples, confirming their insulating behavior. In addition, the G/ω and impedance (Z′ and Z″) analyses demonstrated distinct electrical responses among the conditioning treatments, with the impedance values following the order VW > CW > SW. These findings provide insights into the dielectric behavior of wood under varying surface conditions. Biologically based dielectric materials could facilitate future advancements in insulation components and moisture-sensitive sensing technologies.