GrainboundaryVerluste

GrainboundaryVerluste (grain boundary losses) describe energy dissipation associated with grain boundaries in polycrystalline materials when they are subjected to external stimuli, such as electric fields, mechanical stress, magnetic fields, or acoustic waves. The concept encompasses several distinct mechanisms that arise from the interfaces between differently oriented crystalline grains.

In electrical and dielectric contexts, grain boundaries can act as barriers to charge transport, promoting space-charge accumulation and interfacial polarization. This leads to dielectric losses or an elevated loss tangent, which typically increases with boundary area and can be influenced by boundary chemistry, such as impurity segregation. Models of these losses often invoke interfacial or barrier-layer concepts to account for enhanced dissipation at grain boundaries.

In mechanical and thermo-mechanical contexts, grain boundary sliding and related diffusion processes contribute to energy loss during cyclic loading or at elevated temperatures. Grain boundaries can accommodate strain differently from the grain interiors, causing internal friction and creep that convert mechanical energy into heat.

In magnetic materials, grain boundaries impede domain-wall motion and modify magnetic permeability. Hysteresis losses and frequency-dependent losses can be affected by boundary misorientation, grain size, and boundary chemistry, influencing the overall magnetic dissipation of the material.

In acoustics and elastodynamics, grain boundaries scatter phonons and elastic waves, leading to attenuation and damping of propagating signals. The overall impact of grain boundary losses depends on microstructural features such as grain size distribution, boundary character, and the presence of second-phase or segregated species.

Measurement approaches include impedance spectroscopy to quantify loss tangents, mechanical spectroscopy for internal friction, and microstructural analysis to correlate losses with grain-boundary density and chemistry.