Chen Liu,Lu Bai,Jianming Zhang,Deng Hu,Meng Li,Gaofeng Zeng,Yanfeng Zhang,Wei Wei,Yuhan Sun
Rapid synthesis and characterization of all-silica Deca-Dodecasil 3 Rhombohedral (DD3R) zeolite were systematically studied with (NH 4 ) 2 SiF 6 as silica source. The effects of gel recipe, synthesis temperature and time, seeding, aging and silica source were investigated systematically. Big DD3R crystals (50–150 μm) with various morphologies (hexagonal plate, polyhedron and rhombohedron) were obtained by tuning the synthesis temperature, time, seeding and aging. Compared with other silica sources, (NH 4 ) 2 SiF 6 is very reactive which enhances the nucleation and crystal growth of DD3R zeolite significantly. At 220 °C, highly crystalline DD3R was obtained in 12 h without seeding, which is the fastest synthesis up to now. Aging and seeding reduced the synthesis time substantially and led to smaller crystals. With the help of seeding and aging, pure DD3R crystals were obtained in 6 d at 100 °C, which opens the door to synthesis at low temperature and ambient pressure. Mixed silica sources can reduce the consumption of expensive (NH 4 ) 2 SiF 6 . Higher calcination temperature is required for the complete template removal of the big DD3R crystals obtained in this study, which hinders the diffusion of oxidation products from the template. Zeolites SGT and DOH are competing phases in the synthesis of DD3R. The introduction of Al into the mother liquor led to the formation of zeolite SGT.
Solution-grown hybrid perovskite, FAPbBr3, has attracted great attentions recently due to its inspiring optoelectronic properties and low-cost preparation method. However, challenges of solution growth for FAPbBr3 bulk crystals remain yet, such as uncontrollable crystalline morphologies, irregular shapes, and limited crystal sizes, which are attributed to the dense crystallization nucleus. In this work, we investigate the effects of growth conditions and seed behaviors on the crystallization quality and the yield of FAPbBr3 single crystals. First, the spontaneous nucleation is tailored by optimizing the precursor concentration and heating rate. Furthermore, the seeded crystals are introduced to solve the issues related to the morphology and the yield of single crystals. Based on the above-mentioned investigations, an optimized growth method, a seeded solution method, under a heating rate of 0.1 °C/h is proposed, and centimeter-scale FAPbBr3 single crystals with a very narrow FWHM of high-resolution X-ray diffraction rocking curves and a high yield of ∼100% of single crystals are obtained. The resulting FAPbBr3 single crystal exhibits a bulk resistivity of 3.42 × 109 Ω·cm and a superior ION/IOFF ratio over 104 under 405 nm light at a bias of 10 V. Finally, the pulse height spectra with an energy resolution of ∼21.4% are also achieved based on an AZO/FAPbBr3/Au detector, illuminated using an uncollimated 241Am@5.49 MeV α-particle source at room temperature. This modified seeded solution method shows great potential in preparing high-quality and high-yield perovskite single crystals.
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