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A cost-effective processing route for the production of calcium lanthanum sulfide CaLa 2 S 4 (CLS) via a novel fast fabrication of precursor powders is reported. The sinterability of the newly developed powders was investigated by use of Hot-Pressing and pressureless sintering. Complementary techniques (XRD, SEM-EDS, chemical analysis, SSA, FT-IR spectroscopy) were employed to correlate the sintering processes and parameters to the microstructural/compositional developments and optical performances of the densified ceramics. Dense (>99.8% theor.) and homogeneous CLS ceramics were produced by pressureless sintering at 1250°C for 12 h in H 2 S followed by hot-pressing at 1000°C for 6 h in a powder bed to prevent sulfur loss. Transparency free of impurity absorption has been achieved in the LWIR region (optical transmission of 51% in the 12-14 mm range).
Zinc sulfide transparent ceramics have been fabricated by hot pressing (HP) powders prepared by a newly developed combustion method. Chemical, structural and microstructural properties of powders and ceramics were characterized using different experimental techniques (XRD, SEM-EDS, laser granulometry, TEM, BET, FT-IR spectroscopy). ZnS powders were densified to full density by HP under vacuum atmosphere. The ceramics exhibit highly dense microstructure with mean grain size of 1 µm. TEM characterization identified, both in powders and ceramics, twins and simple stacking faults due to the aperiodic distribution of hexagonal domains. With optical transmission of the theoretical level (75%), without absorption band (at 6 µm) and with negligible optical loss, in the 4-12 µm region, the ceramics exhibit better optical performances than standard grade CVD ZnS, and unprecedented performances for hot-pressed ZnS.
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