In recent years, there have been continuous research reports on new oxide solid acids, among which the research on the fifth subgroup elements (V, Nb, Ta) has always been the focus of solid acid research. In industry, niobium pentoxide and tantalum pentoxide are collectively referred to as earth acids. Wet tantalum oxide (hydrated Ta2O5), niobium oxide (Nb2O5) are all excellent properties of the potential of solid acid catalyst. Niobium has very important research value, so we first give a systematic overview of the element niobium and its compounds.
Niobium and oxygen can form five oxides: NbO, Nb02, Nb2O, Nb6O and Nb2O5, among which only Nb205 is the most stable. Niobium pentoxide has a hexahedral structure of niobium oxide. Niobium penoxide is widely used in the production of ceramic capacitors because of its good dielectric properties. Thin-film niobium oxide can be used to produce resistance and capacitance components for integrated circuits. Niobium penoxide is also a special optical glass manufacturing material, which can achieve high refractive index and low dispersion. Niobium not only forms oxides as a metal, but also forms similar oxygen-containing niobates like the P element in the fifth group. Most niobates are insoluble in water, and potassium niobate has the highest solubility of all niobates. Many niobate crystals have the property of spontaneous polarization and are good dielectric materials.
Niobium oxide (Nb2O5) has a variety of crystalline phases, nearly 15 of which have been reported. Among them, the most common crystal types are pseudohexagonal phase system (tt-nb2o5), orthogonal crystal system (t-nb2o5) and monoclinic crystal system (h-nb2o5). At different temperatures, various crystal phases transform into each other. H-nb2o5 is the most stable crystalline phase, and h-nb2o5 is usually formed when heated to more than 1000℃, while TT- and m-nb2o5 are the most unstable crystalline phases.
Basic electrical characteristics of NbO capacitors include: capacity range: 10 F~470 F, rated up to 1000 F, housing dimensions in accordance with EIA a-e standards. AVX’s OxiCapGeneric series NbO capacitors have a reliability of 0.5%/1000 hours (twice as high as tantalum capacitors) and the Performance series have a reliability of 0.2%/1000 hours.
Reliability NbO capacitors have very effective self-healing properties, thus ensuring superior reliability over other commercial capacitor technologies. The Performance series has reliability specifications up to 0.2%/1000 HRS, for example MTBF(mean time of failure) of 500,000 HRS. The Generic series has a reliability of 0.5%/1000 hours, for example MTBF of 200,000 hours. This level of reliability is higher than most existing commercial grade capacitors.
Anti-ignition failure mode
The ignition energy of niobium oxide is two grades higher than that of tantalum and niobium, and the specific heat is twice that of tantalum and niobium, and the ignition failure mode is significantly reduced (95%). In addition, the electrical stress in the medium is small (after applying the voltage, compared with Ta 2 O 5, Nb 2 O 5 medium is more dense, so at a certain rated voltage, Nb 2 O 5 can work at a lower field strength), which can load a larger ripple current and reduce the voltage loss in the low impedance circuit. Niobium oxide electrolytic capacitor has a high resistance to short-circuit failure mechanism, and the oxide basis significantly improves the thermal failure impedance after dielectric breakdown. Compared to tantalum or niobium capacitors, niobium oxide electrolytic capacitors offer true “non-combustion” technology, whether or not they have a polymer electrolyte system.
Suitable for lead-free system
Lead-free assembly system requires higher reflux temperature and thermal mechanical stress. These harsh conditions limited capacitor technology. Aluminum and foil capacitors are extremely sensitive to thermally mechanical loads, especially for reflux temperature/time welding curves that can result in severe electrical failure. Ceramic capacitors are most resilient to electrical overstress, so they can be adapted to lead-free assembly in terms of thermal mechanical loads. However, larger ceramic parts are sensitive to the bending of the circuit board and must be made to the manufacturer’s specifications. The common cause of ceramic failure is low insulation resistance or short circuit failure. The new niobium oxide capacitors are particularly striking because, like ceramic capacitors, they exhibit excellent stability under thermally mechanical stress and high temperature peak reflux (lead-free assembly) without any response to mechanical weaknesses.
No piezoelectric effect
The high CV characteristics of barium titanate (the main ceramic material in most dielectric systems) exhibit a chatter effect. For example, when a dc bias is applied with a superimposed signal (such as a 1kHz sine wave), the Y5V capacitor begins to “buzz”. This process is also reversible, and the 1kHz external signal will also generate 1kHz noise to the electrical signal. Niobium oxide capacitors also use ceramic powders, but do not have this chatter effect.
Less weight
The proportion of niobium oxide powder is half that of tantalum powder, which will affect the total weight of the capacitor. The e-type niobium oxide capacitor, for example, is about 25 percent lighter than the same size capacitor made from tantalum powder. For the same component occupation area, lighter weight can also improve PCB drop test strength, which is also an important parameter for practical applications.
ESR is small at higher temperatures
The temperature-dependent properties of N b O capacitors are the same as those of tantalum capacitors. As the conductivity of MnO 2 (second electrode) improves, ESR(effective series resistance) decreases with temperature. Therefore, the filter performance at higher temperature is better than that at room temperature of 25℃
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