Tungsten Oxide

Tungsten oxide (WO3) is an extremely important high-tech materials, this material is non-linear, high-dielectric constant, electrochromic, with gas detection, chemical catalysis and other features. For the features of WO3, the nano-powder of WO3 can be fired into varistor ceramics, ceramic capacitors, light (electricity) color ceramic film, gas-sensing ceramics, photocatalytic degradation ceramic membrane, battery electrode ceramic materials, microwave absorbing ceramic film, new high-temperature thermoelectric ceramics and functional ceramics and ceramic films, which has great potential in many chemical, energy, electricity and other fields. There are two preparation methods of ceramic raw materials, that mechanical disruption and synthesis. The former one uses mechanical principle crushing coarse particles to obtain fine powder, which has the advantages of large amount of production and low cost, but there are problems of impurities mixed in the crushing process, and it is dif...

The nonlinear tungsten oxide ceramic (pressure-sensitive behavior) was first reported by Makarov in 1994, and it’s pointed out that it can be used as a low pressure-sensitive materials in the field of microelectronics since the WO3 ceramics has low varistor voltage. But there are not further studies and reports in earlier studies about behavior origin and mechanism of WO3 ceramics issues. Research shows that the varistor characteristics of WO3 ceramic is different from traditional ZnO and SnO2 Varistor material, the conventional Schottky barrier model can not explain the behavior of WO3 ceramic varistor yet, so the conventional grain boundary Schottky barrier model needs to be modified. In view of which, WO3 ceramics was prepared, and the mechanism of the pressure-sensitive characteristics were studied, and amendments WO3 ceramic grain boundary Schottky barrier model was proposed. Undoped WO3 ceramics sintered has obvious varistor behavior, AES spectra shows the ceramic crys...

Tungsten oxide film is an important functional material, it’s been used in the system because of its excellent electrochromic properties. The main evaporation materials used in Electron beam evaporation preparing electrochromic WO3 film are WO3 powder and WO3 target. More current research is on the WO3 powder as evaporation material, but the form of powder is generally inappropriate, so the evaporation material is chosen. So choosing WO3 target as a evaporation material is an optimization program. However, there are few reports of WO3 target preparation at home or abroad. WO3 target prepared in domestic laboratories has disadvantages of low density or impure, so the preparation of high purity and high density WO3 target is significant. To prepare high purity ultra-compact WO3 target, it can be researched in powder, forming and sintering, the optimal combination of which is the necessary condition to achieve the above goals.  (1) Preparation of WO3 powders of high purity,...

A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. In contrast to a diode however, it has the same characteristic for both directions of traversing current. At low voltage it has a high electrical resistance which decreases as the voltage is raised. Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltages. When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered. In recent years, studies on low-voltage varistor materials have gotten widespread attention, such as TiO2, Sr TiO3 and WO3. In 1994, tungsten oxide ceramics nonlinear behavior was first reported. The study shows that WO3 ceramic materia...

Functional ceramics have many excellent properties in electricity, magnetism, sound, light, heat, etc. that make it difficult for other material to match, and some have more than one function. And these properties usually depends on the internal electronic state or structure of the atomic nucleus. It’s also known as electronic ceramics. It has been widely used in energy development, electronic technology, sensor technology, laser technology, photonics technology, infrared technology, biotechnology, environmental science and other aspects. In addition, the semiconductor ceramic, the insulating ceramic, the dielectric ceramic, luminescent ceramics, photosensitive ceramic, absorbing ceramics, ceramic laser, a ceramic nuclear fuel, propellants ceramics, ceramic converting solar light into energy storage and ceramics, ceramics solid battery, ceramic damping biotechnology ceramics, catalysis ceramics, film and other special functions, which also play important roles in automatic control, in...

Cesium is a golden yellow metal, low melting point active metal, easily oxidized in air and can react violently with water to produce hydrogen and even explode. There is no elemental form of cesium in nature, cesium minimal distribution in the ocean in the form of cesium salt. Cesium tungsten bronze is widely used because of its low resistance, excellent visible light transmittance, near-infrared shielding properties. Also it is widely used in preparing conductive thin film, since being the glass transparent insulation coating as insulating agent, it has excellent properties like low resistance, excellent visible light transmittance and near-infrared shielding performance. The article provides a method that using ammonium paratungstate and cesium nitrate as raw materials to produce Cesium-tungsten oxide ultrafine powder, the specific steps are as follows: 1. Weighing the cesium nitrate, ammonium paratungstate by the molar ratio of Cs/W being 1: (1.5 to 2.8), and adding chelating agen...

Under certain conditions the six-phase tungsten oxide （h-WO 3 ）can exist in stable form. When annealing temperature exceeds 400℃, it can turns into monoclinic system（γ-WO 3 ）. Nano tungsten oxide applied in electric and optical field is different from tungsten oxide bulk. The main differences are phase transition temperature drops evidently, so sometimes orthorhombic tungsten oxide（β-WO 3 ）appears and is stable under room temperature. Chemical stoichiometric number of tungsten oxide seems simple, its phase transition and structure change is complex. The ideal tungsten oxide is octahedron, W 6+   exists in the center part of it. O 2  as anion distribute in the other eight edges. Actually, W 6+   often deviates from the center part, the whole structure turns into tetragonal crystal（α-WO 3 ）, temperature range is T>740℃. For orthorhombic system, 740℃>T>330℃; monoclinic system: 330℃>T>17℃ and triclinic system: 17℃>T>-43℃. Below are SEM gr...