New lead-free chemistry for in-situ monitoring of advanced nuclear power plant

Nuclear power is essential for sustainable energy infrastructure and economic development,necessitating materials for high-radiation environments that can facilitate visualization and observation.Conventional lead glass is inadequate for future requirements due to radiation-induced darkening,poor mechanical properties,and toxicity.Therefore,there is urgent to find new window materials that offer multi-ionization shielding(particularly against deep-penetrating gamma ray,γ,and neutron,n,radiations),desirable opto-mechanical properties,service stability against darkening,and non-toxicity.In this study,we report a family of transparent rare-earth pyrochlore ceramics La_(x)Gd_(2-x)Zr_(2)O_(7),offering unique chemo-physical properties that are ideal for robust radiation shielding windows.Remarkably,we demonstrated the capability of maintaining high transparency under heavy-dose exposure to 1000 kGy ^(60)Coγradiation.We observed the service stability against radiation darkening can be greatly enhanced with La-rich compositions,while Gd-rich compositions undergo shallow darkening that can be reversibly recovered under visible light.This behavior is attributed to mitigated oxygen migration from 48f to 8a in La-rich compositions,which have high pyrochlore phase stability and well-ordered atomic structures,and reversible oxygen migration between 48f and 8a in Gd-rich compositions,which remain active at room temperature.Our proposal and demonstration unlock ample opportunities in designing functional transparent ceramics as window materials for demanding applications in high-radiation environments.

Defect elimination to enhance photoluminescence and optical transparency of Pr-doped ceramics for self-calibrated temperature feedback windows

Pr-doped metal oxide polycrystalline transparent ceramics are highly desirable for photothermal window systems served in extreme environments;however,obtaining efficient photoluminescence(PL)together with high transparency in these ceramics is still posing serious challenges,which undoubtedly limits their applications.Here,Pr-doped Y_(2)Zr_(2)O_(7)(YZO)transparent ceramics,as an illustrative example,are prepared by a solid-state reaction and vacuum sintering method.Owing to the elimination of defect clusters[Pr_(Y)^(4+)-O^(2-)Pr_(Y)^(4+)]and[Pr_(Y)^(4+)-e′]without the introduction of impurities and additional defects,the fabricated YZO:Pr ceramics exhibit high transparency(74%)and efficient PL(39-fold enhanced)after air annealing plus vacuum re-annealing treatment.Moreover,upon 295/450 nm excitation,the emission bands(blue,green,red,and dark red)from YZO:Pr ceramics present different temperature-dependent properties due to the thermalquenching channel generated by the intervalence charge transfer(IVCT)state between Pr_(Y)^(4+)and Zr^(4+)ions.Furthermore,a self-calibrated temperature feedback window with the same fluorescence intensity ratio(FIR)model(I_(613)/I_(503),where I represents the intensity)under different excitation light sources(295 and 450 nm)is designed.The developed photothermal window operated in a wide temperature range(303-663 K)shows relatively high sensitivities(absolute sensitivity(Sa)and relative sensitivity(S)reach 0.008 K^(-1)at 663 K and 0.47%K^(-1)at 363 K,respectively),high repeatability(>98%),and low temperature uncertainty(T<3.2 K).This work presents a paradigm for achieving enhanced PL along with elevated transparency of lanthanide(Ln)-doped ceramics through vacuum re-annealing treatment engineering and demonstrates their promising potential for photothermal window systems.

Extraction of the dynamic plastic behavior of AlON single crystals by nanoimpact

Investigating the dynamic mechanical behavior of single-crystal aluminum oxynitride(AlON)is fascinating and crucial for understanding material performance in relevant applications.Nevertheless,few studies have explored the dynamic mechanical properties of AlON single crystals.In this study,a series of nanoimpact experiments(representative strain rateε˙r≈102s^(-1))were performed on three principal orientations((010),(101),and(111))of grains to extract the dynamic mechanical responses of AlON single crystals.Our results reveal that the dynamic plasticity of an AlON single crystal is governed by a combination of mechanisms,including dislocation motion and amorphization.Significantly,the localized amorphization induced by mechanical deformation has a softening effect(a lower dynamic hardness).The crystallographic orientation affects the dynamic hardness similarly to the static hardness.In particular,the(111)orientation results in the highest hardness,whereas the(010)orientation is the softest among the three principal orientations.This dependency aligns with the expectations derived from applying Schmid law.Furthermore,both the dynamic and static hardnesses exhibit typical indentation size effects(ISEs),which can be effectively described via the strain gradient theory associated with the geometrically necessary dislocations.In addition,the size and rate dependencies of the dynamic hardness can be decoupled into two independent terms.