Effects of tungsten source and tartrate additive on the microstructure and photoluminescence of hydrothermally crystallized ZnWO4

• Published in: Tungsten 2019-12, Vol.1 (4), p.266-275
• Main Authors: Li, Mei-Ting, Li, Ji-Guang, Zhu, Qi, Kim, Byung-Nam
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; Crystallites; Crystallization; Diameters; Diffraction; Fourier transforms; Luminescence; Materials Engineering; Materials Science; Metallic Materials; Morphology; Nanocrystals; Nanorods; Nuclear Chemistry; Original Paper; Particle and Nuclear Physics; Photoluminescence; Scanning electron microscopy; Thickness; Tungsten; Zinc tungstates
• ISSN: 2661-8028; 2661-8036
• DOI: 10.1007/s42864-019-00030-9

Tungstate source and tartrate (Tar 2− ) additive were examined for their influences on the hydrothermal formation and characteristics of ZnWO 4 nanocrystals. It was clearly shown that quasi-equiaxed nanocrystallites of ~ 50–100 nm in diameter and nanorods of ~ 40–50 nm in diameter and up to ~ 700 nm in length can be generated with (NH 4 ) 10 W 12 O 41 ·5H 2 O and K 2 WO 4 ·2H 2 O as tungsten sources, respectively. Introducing Tar 2− into the K 2 WO 4 ·2H 2 O reaction system effectively transformed the primary crystallites of ZnWO 4 from nanorods into quasi-equiaxed nanocrystals (~ 20–50 nm) and then nanoplates (thickness of ~ 20 nm, lateral size of ~ 200 nm) and, meanwhile, aggregated the crystallites into spheroidal clusters (~ 2–3 µm in diameter) with the increasing Tar 2− /Zn 2+ molar ratio up to ~ 2. Optical spectroscopy revealed that the ZnWO 4 products exhibit broad-band photoluminescence (~ 425–700 nm) through 3 T 1u  →  1 A 1g transition of the [WO 6 ] 6− ligand under short ultraviolet excitation and the nanorods show the best luminescence among all tested samples. Calcination at 500 °C may effectively remove the adsorbed Tar 2− species and greatly improve luminescence of the samples synthesized in the presence of Tar 2− .