Enhancing the stability of piezoelectric properties is essential for ensuring the reliability of high-temperature piezoelectric sensors. In this study, we have synthesized AlN piezoelectric crystals as representative materials and employed first-principles methods to investigate their temperature-dependent piezoelectric properties. By integrating the effects of lattice expansion and electron–phonon interactions, we accurately constructed the crystal structure of AlN across a wide temperature range and successfully predicted its piezoelectric behavior. Theoretical analysis reveals that ion polarization driven by lattice distortion and elastic softening of chemical bonds maintains the overall structural integrity of defect-free AlN single crystals, resulting in a stable piezoelectric coefficient d₃₃ with a deviation of only 8.55% at temperatures up to 1300 K. However, experimental results indicate that the stability of the piezoelectric performance of the grown AlN crystals is disrupted at temperatures above 870 K. This temperature limitation is attributed to point defects within AlN crystals, particularly those caused by oxygen-substituted nitrogen (O_N). These findings provide valuable guidance for enhancing the piezoelectric temperature stability of AlN crystals through optimized experimental conditions, such as oxygen atmosphere treatment and defect modification during crystal growth.

Gallium nitride (GaN) single crystal with prominent electron mobility and heat resistance have great potential in the high temperature integrate electric power systems. However, the sluggish charge storage kinetics and inadequate energy densities are bottlenecks to its practical application. Herein, the self-supported GaN/Mn₃O₄ integrated electrode is developed for both energy harvesting and storage under the high temperature environment. The experimental and theoretical calculations results reveal that such integrated structures with Mn-N heterointerface bring abundant active sites and reconstruct low-energy barrier channels for efficient charge transferring, reasonably optimizing the ions adsorption ability and strengthening the structural stability. Consequently, the assembled GaN based supercapacitors deliver the power density of 34.0 mW cm⁻² with capacitance retention of 81.3% after 10000 cycles at 130 ℃. This work innovatively correlates the centimeter scale GaN single crystal with ideal theoretical capacity Mn₃O₄ and provides an effective avenue for the follow-up energy storage applications of the wide bandgap semiconductor.