Scalable Production of Photochromic Yttrium Oxyhydride Powder via Ball Milling

TL;DR

This paper presents a scalable method to produce photochromic yttrium oxyhydride powders via reactive ball milling, enabling practical applications and mass production of this promising material.

Contribution

It introduces the first scalable synthesis of YHO powders using ball milling, overcoming previous thin film deposition limitations.

Findings

YHO powders exhibit strong photochromic response at 850 nm under 405 nm light.

The powders show reversible cycling and memory effects similar to thin films.

YHO powders can be incorporated into polymer composites for patterning applications.

Abstract

Yttrium oxyhydride (YHO) represents one of the most promising photochromic materials discovered in recent years, yet its practical deployment has been severely constrained by the limitations of thin film deposition methods. Here we demonstrate the first successful synthesis of photochromic YHO powders through reactive ball milling under hydrogen atmosphere followed by controlled oxidation a fundamentally scalable approach that overcomes the production barriers facing this technology. High-energy planetary ball milling of yttrium metal under 50 bar hydrogen for 20 hours, followed by controlled oxidation in ultra-dry technical air, yielded nanostructured YHO powders with less than 500 nm particle sizes. These powders exhibit robust photochromic response with reflectance modulation at 850 nm under 405 nm excitation, reversible cycling behavior, and the characteristic memory effect previously observed only in thin films. Powder X-ray diffraction confirms the formation of the cubic YHO phase with lattice expansion consistent with oxygen incorporation into the yttrium hydride structure. Critically, we demonstrate that YHO powders can be processed into polymer composites enabling spatially-resolved photochromic patterning a capability essential for practical device applications. While optimization of optical contrast remains an opportunity for future work, this powder synthesis route fundamentally transforms the manufacturing of YHO-based photochromic systems, enabling mass-scale production using established industrial ball milling infrastructure. These findings establish a viable pathway toward commercial deployment of YHO in smart windows, adaptive optics, and rewritable information storage applications.