Multi-mode optical modulation and superior energy storage in Eu/La co-doped KNN transparent ferroelectric ceramics

Ferroelectric transparent ceramics serve as pivotal functional materials with inherently tunable polarization. However, addressing the intrinsic trade-off between high optical transparency and robust ferroelectricity remains critical for breakthroughs in multifunctional optoelectronic coupling applications. Herein, designing relaxor ferroelectric transparent ceramics via rare-earth doping is an effective strategy, which refines grain size, introduces polar nanoregions and induces high-symmetry phase structure. It synergistically achieves high transmittance and polarization, laying the foundation for one-structure multi-photoelectric-effects coupled applications. Accordingly, superior energy storage density ( W tot  = 10.5 J/cm 3 , W rec  = 7.0 J/cm 3 ) and optical transmittance (78 % at 780 nm) are simultaneously realized in Eu 3+ /La 3+ co-doped K 0.5 Na 0.5 NbO 3 (KNN) ceramics, along with excellent photochromic-induced transmittance and luminescence reversible modulation (ΔAbs = 19.35 %, ΔR t  = 92.5 %), outperforming previously reported KNN-based multifunctional ceramics in terms of comprehensive performance. This study proposes a viable approach to pave the way for constructing smart materials that can modulate photoelectric performance while extending their functionality.