A Novel Strategy for Synthesizing Matrix-Matched Microanalysis Reference Materials via Hydrothermal Precursors and Ultrahigh-Pressure Sintering

Secondary-ion mass spectrometry (SIMS) and related in situ microanalytical techniques allow precise chemical
and isotopic characterization
at micron and submicron scales, providing insights into spatially
heterogeneous processes. However, the quantitative accuracy of SIMS
is limited by matrix effects, which cause instrumental mass fractionation
(IMF) between measured and true isotope ratios. Accurate quantification
requires matrix-matched reference materials (RMs) with identical physical
and chemical properties to the unknown samples. Most existing SIMS
RMs are derived from natural minerals, which often exhibit heterogeneity,
limiting reproducibility and interlaboratory comparability. Synthetic
RMs offer a promising solution, but their development for SIMS has
been challenging due to the sensitivity of SIMS to microstructural
attributes such as surface smoothness and grain size. This study presents
a novel synthesis strategy for producing matrix-matched pyrite (FeS2) RMs. By combining hydrothermal precursor synthesis with
low-temperature ultrahigh-pressure (UHP) sintering, we fabricated
dense, nanocrystalline pyrite ceramics with controlled stoichiometry
and exceptional sulfur-isotope homogeneity. The resulting material
exhibited sputtering behavior indistinguishable from that of natural
pyrite, demonstrating the strategy as a robust framework for producing
synthetic sulfide RMs. This approach facilitates the improvement of
analytical accuracy and reproducibility in microanalytical science
and can be extended to other mineral systems.