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

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 Eu 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 EuWO and EuWO. 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.