Transparent nanoceramics embedded with highly dense crystalline domains are promising for applications in missile guidance, infrared night vision, and laser and nuclear radiation detection. Unfortunately, current nanoceramics are strictly constrained by the stringent construction procedures such as super‐high pressure and containerless processing. Here, a pressureless crystallization engineering strategy in glass for elaboration of transparent nanoceramics and fibers is proposed and experimentally demonstrated. By intentional creation of a sharp contrast between nucleation and growth rates, the crystal growth rate during glass crystallization can be significantly suppressed. Importantly, this unique phase‐transition habit enables the achievement of transparent nanoceramics and even smooth fibers with extremely tiny crystalline size (≈20 nm) and high crystallinity (≈97%) under atmospheric pressure. This allows the generation of an attractive nonlinear optical response such as dynamic optical filtering and luminescence in the mid‐infrared waveband of 4300–4950 nm. These findings highlight that the strategy to switch the phase‐transition habit of glass into the unconventional crystallization regime may provide new opportunities for the creation of next‐generation nanoceramics and fibers.

The construction of transparent ceramics under mild conditionsand standard atmospheric pressure has great scientific and technological potential; however, it remains difficult to achieve when conventional ceramic sintering techniques are used. Herein, a mild strategy for constructing dual‐phase optical ceramics with high crystallinity (>90%) based on the stepped dual‐phase crystallization of hybridized aluminosilicate glass is presented. Theoretical and experimental studies reveal that the hybridization of the glass system enables a new balance between the glass‐forming ability and crystallization and can overcome the uncontrolled devitrification phenomenon during the dense crystallization of glass. Transparent hybridized oxide‐fluoride ceramics with fiber geometry and dual‐phase microstructures are also successfully fabricated. The generality of the strategy is confirmed, and transparent ceramics with various chemical compositions and phase combinations are prepared. Additionally, the cross‐section of the ceramic fibers can be easily tuned into a circle, square, trapezoid, or even a triangle. Furthermore, the practical applications of optical ceramics for lighting and X‐ray imaging are demonstrated. The findings described here suggest a major step toward expanding the scope of optical ceramics.

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Developing light-harvesting materials with broadband spectral response has constantly been at the forefront of photonics and materials science. The variation in dopants and hosts allows for extension of spectral response, but construction of broadband down-conversion phosphor covering the entire ultra-violet region remains a daunting challenge. Here, we describe a material system in which amorphization and N-doping notably extend the spectral response. We demonstrate that the fabricated nitrided amorphous TiO 2 activated with high concentration of Eu 3+ (∼15 mol %) can be excited by X-ray and ultraviolet light (200−400 nm) and present intense visible luminescence. We use hybrid density functional theory to perform structure simulation and clarify that N-anchoring is mediated by coordinately Ti−N bonding between the N lone pairs and the Ti IV center. Accordingly, the simultaneous structure disordering and nitriding in semiconductors as demonstrated here in TiO 2 :Eu 3+ could be extended to other host and dopant systems for applications ranging from spectral modification to X-ray detection.

The effective removal of hydroxyl groups (OH) is receiving the attention of scientists interested in developing high-performance photonic glass. Previous approaches rely on stringent control of the various drying techniques which meet with limited success in silicate glass obtained by the sol-gel method. Here, we present a novel in situ strategy to remove structural OH groups, based on the self-limited nanocrystallization-triggered local chemical reaction between OH and F À in the glassy phase. The experimental data revealed that a more than 100-fold increase in the emission intensity can be realized. Moreover, the mechanism was discussed and it can be attributed to the effective removal of structural OH with especially strong binding energy. The results suggest an innovative avenue for the development of photonic glasses with efficient luminescence, excellent optical transmission, and improved reliability.