Force-light-heat stimulation-induced multicolor chromism and multifunctional applications of europium tungstate phosphor.

Abstract

Stimulus-responsive chromogenic luminescent materials are promising for security and optical storage, yet force-induced color change in inorganic materials remains rarely reported. Here we report a europium tungstate that exhibits mechanochromism, driven by pressure-induced tungsten valence transformation and color center formation. The sample color shifts from orange to black with increasing pressure, accompanied by a linear variation in reflectance. A luminescence modulation rate of 100% for Eu³⁺ is achieved due to the strong reabsorption of the black state. Negative photochromism, switching from black/orange to white, occurs under laser irradiation or heating via the reversible phase transition between EuWO₄ and Eu₂W₂O₉. The luminescence modulation is attributed to the synergistic effects of body color reabsorption and nonradiative transitions. Our work demonstrates a robust inorganic material responsive to force, light, and heat, offering versatile functionality for pressure sensing, anti-counterfeiting, and optical storage, and provides a design strategy for multicolor chromogenic materials.