Tungsten Oxide Target Densification

Tungsten oxide film is a widely studied functional material. It has excellent short-wavelength transmission, and the forbidden band width is easily adjusted by doping. Through ion implantation, ultraviolet photon irradiation, and gas molecule adsorption, its optical and electrical properties will change significantly, so it is displayed on optical glass and flat panel. There are wide application prospects in the fields of photoelectric conversion, electrochromism and photochromism.

The preparation methods of tungsten oxide thin films include physical vapor deposition, chemical vapor deposition, spray pyrolysis, anodization, electrodeposition, sol-gel and so on. Among them, tungsten oxide films prepared by physical vapor deposition are widely used because of their high bonding strength, high deposition efficiency and mature and stable technology. In order to prepare tungsten oxide thin films by physical vapor deposition, dense tungsten oxide target is used. Tungsten oxide in tungsten oxide target is bombarded and gasified by energy beam, and then deposited on the surface of the substrate. Due to the low self-diffusion coefficient of pure tungsten trioxide and melting at about 1470 ℃, it is difficult to sinter compactly. If sintering additives are added, the photoelectric properties of vapor deposited tungsten oxide films are affected by impurities.

The densification of tungsten oxide targets is a technical problem. The researchers tried to densify the tungsten oxide without adding any sintering aids, so that the sintered tungsten oxide target has a purity higher than 99% and a density greater than 6.7. g/cm³, the process includes:

The tri-oxidized powder (average fineness of 17 um) is doped with 1-5% by weight of polyethylene glycol (PEG) as a molding agent, and is added to distilled water for wet grinding in a ball mill for 24-96 hours, and after drying and sieving, at 100-200 MPa. Pressing and forming under pressure, after de-forming agent, in a high-temperature furnace in a bismuth aluminum bar furnace, sintering at atmospheric pressure in air at 1110 °C - 1400 °C for 60-180 minutes, with furnace cooling, thus obtained sintered tungsten trioxide, The purity is higher than 99%, and the density is greater than 6.75 g/cm³ (relative density ≥ 94%).

The above process is suitable for ordinary tungsten oxide powder raw materials (powder fineness 5-30 microns) and also for ultrafine tungsten oxide powder raw materials (less than 5 microns), and can be prepared with high purity without adding any sintering aid. High-density sintered tungsten oxide, which is made into various complex shapes economically and efficiently.

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