Effect of Temperature on Crystal Structure of W Films Electrodeposited from Molten CsF–CsCl–WO 3

• Published in: Journal of the Electrochemical Society Vol. 169; no. 10; p. 102506
• Main Authors: Norikawa, Yutaro, Meng, Xianduo, Yasuda, Kouji, Nohira, Toshiyuki
• Format: Journal Article
• Language: English
• Published: 01.10.2022
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1945-7111/ac9760

The electrodeposition of W was studied in detail using CsF–CsCl–WO 3 . Prior to electrodeposition, the WO 3 solubility was confirmed to be 1.0 mol% at 773 K and increase with temperature. To investigate the effect of temperature on the crystal structure, electrodeposition was conducted at 6–25 mA cm −2 between 773 and 923 K with a unified charge density of 90 C cm −2 . X-ray diffraction analysis confirmed that the crystal structures of the electrodeposited W films were β -W at 773 and 823 K, a mixed phase ( α -W and β -W) at 873 K, and α -W at 923 K. The shape of the crystal grains varied with temperature: grains of β -W obtained at 773 and 823 K were spherical, while those of α -W obtained at 923 K were angular. Scanning electron microscopy observations showed that W films with smoother surfaces were obtained at lower current densities at all temperatures. In particular, a dense and smooth W film (surface roughness: 0.66 μ m, thickness: 10 μ m) was obtained at 6 mA cm −2 and 773 K. When the charge density was increased to 210 C cm −2 at 6 mA cm −2 and 773 K, a W film with a smooth surface and thickness of 30 μ m was obtained.