Overview of the Properties of Tantalum Compounds

Tantalum oxide

The most useful tantalum oxide is tantalum pentaoxide (Ta2O5). Ta2O5 is white fine crystal powder, tasteless and odorless, with a specific gravity of 8.71g/cm3 and a melting point of 1870℃. Tantalum is amphoteric but apparently acidic, insoluble in water, most acids, and bases, but slowly dissolved in hot hydrofluoric and peroxy acids.

tantalum oxide

Ta2O5 has both α and βvariants, and its transition temperature is 1320℃, beyond which Ta2O5 turns white to gray. Different oxides have different crystal structures, so their lattice constants, densities, and other properties are obviously different. It is known that amorphous Ta2O5 begins to crystallize at 500℃ to form a low-temperature crystal (T type), converts to a temperature crystal (M type) at 830℃, and forms a high-temperature crystal (H type) at more than 830℃.

Tantalum halide

In tantalum halides, halogens in high-priced pentahalides are more easily replaced by oxygen to form stable halogen oxides. Most of the halogens of tantalum are volatile compounds, among which fluoride is well soluble in water and only partially hydrolyzed.

Tantalum(V) chloride (TaCl5) is a white powder and yellow when it is not pure. It has a melting point of 220℃, a boiling point of 223℃-239℃, and a specific gravity of 3.68g/cm3. It is volatile and has strong moisture absorption. It is unstable at high temperatures and decomposes to form metal tantalum at vacuum temperatures above 800℃. In addition to the high-priced TaCl5, the low-priced chlorides of tantalum include TaCl4, TaCl3, and TaCl2, which are volatile substances.

Tantalum bromide (TaBr5) is an orange crystal, soluble in water and hydrolyzed, soluble in methanol, ethanol, and CCl4, and soluble in aniline and liquid ammonia for reactions. Tantalum iodide (TaI5) is a black crystal that can be heated to sublimate without decomposition and readily hydrolyzes in moist air, releasing hydrogen iodide.

Tantalum carbide

Ta2C and tantalum carbide (TaC) are the main carbides of tantalum, and Ta2C has both alpha -Ta2C and beta -Ta2C isomers. TaC is a dark brown powder with a melting point of 3880℃, a boiling point of 5500℃ and a density of 14.4g/cm3. It has good chemical stability and can only be dissolved in mixed solutions of nitric acid and hydrofluoric acid. The carbide of tantalum is not easy to be oxidized in the air when the temperature is lower than 1000 ~ 1100℃. Nitrogen compounds are readily formed by the action of nitrogen or ammonia.

Tantalum hydride

Tantalum hydrides are very stable at room temperature in the air. Hydrogen is released by decomposition when heated to 1000 ~ 1200℃ under a high vacuum. Below 350℃, tantalum almost has no interaction with hydrogen, and the reaction speed increases with the increase of temperature. At a certain temperature and pressure, the maximum hydrogen content in tantalum hydride corresponds to H/Ta of 0.02 ~ 0.08(TaH0.2 ~ TaH0.8).

Tantalum nitride

There are three kinds of tantalum nitride: TaN, Ta2N, and Ta3N5. Tantalum nitrite is a bluish-gray powder with a melting point of 2980 ~ 3090℃ and a density of 14.4g/cm3. It is insoluble in nitric acid, hydrofluoric acid, and sulfuric acid, but soluble in hot alkaline solution and releases ammonia or nitrogen. Tantalum nitride generates oxides when heated in air, releasing nitrogen.

Tantalum selenite

TaSe2, its resistivity is 2.23 x 10-3 Ω. Cm, with the relative friction coefficient of 0.08 in the air at room temperature, the oxidation temperature of 600 ℃ in air, and the decomposition temperature of 900 ℃ in a vacuum.

Tantalum silicone

The main silicide of tantalum is TaSi2, and there are also some other compounds such as Ta2Si and Ta5Si3. Ta2Si has a melting point of 2200 ℃, a density of 8.83 g/cm3 and a resistance of 8.5 Ω. Cm. It is not eroded by mineral acids, but can be decomposed by hydrofluoric acid, and can be completely decomposed by molten Na2CO3 and NaOH.

Tantalate

Ta2O5 can be fused with oxides, hydroxides, or carbonates of more than 50 elements from all 8 groups in the periodic table of chemical elements to form various complex types of tantalates, which may be expressed in the following general formula: xMeO•yTa2O5 (Me = alkali metal).

Almost all alkali tantalates have a high degree of polymerization in aqueous solution and are insoluble compounds in water solution. Alkali tantalate can be reduced by hydrogen: 2MeTaO3+H2=Me2O+2TaO2+H2O, with a reaction temperature of 600~700℃. Except for alkali tantalates, most tantalates are insoluble in water.

Most tantalate crystals (such as lithium tantalate) are ferroelectric. They belong to the category of thermoelectric devices that have spontaneous polarization. Their polarization value is related to electric field voltage and has Curie temperature. Tantalum ferroelectric materials also have the characteristics of voltage, electro-optic and nonlinear optics. Some tantalates are semiconductor materials with narrow channels and are important materials for manufacturing electronic industrial components.

Stanford Advanced Materials supplies high-quality tantalum products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.

Applications of Tantalum in the Electronic Industry

Tantalum and its alloy have a high melting point, corrosion resistance, excellent high-temperature strength, and are free of radioactive, etc, are widely used in the electronics industry, chemical industry, aerospace, weapon system, the medical field, etc. Applications of tantalum materials in the electronic industry mainly include tantalum capacitors, integrated circuits, electron tubes, storage devices, and passive devices.

tantalum

Tantalum Capacitors

Tantalum capacitors have strong corrosion resistance and can maintain stable electrical and physical and chemical properties under various environmental conditions. In addition, it also has a high resistance rate (7.5 x 1012 Ω cm), a large dielectric constant (27.6), and a small leakage current.

Tantalum Capacitors
Tantalum Capacitors

Tantalum has the characteristics of a valve metal, and the dense oxide film generated on its surface has unidirectional conductivity, which is suitable for capacitors. Tantalum capacitors are large in capacity and small in volume. Their capacitance is three times that of aluminum capacitors, while their volume is much smaller than that of aluminum capacitors. The tantalum capacitor has a working temperature range of 80 ~ 200 ℃, so it can meet the demand of different temperatures. In addition, tantalum capacitors also have strong stability and heat resistance, which makes them highly reliable materials in the electronics industry, as well as widely used in military and high-tech fields that need to ensure high reliability.

Integrated circuit

Tantalum has been introduced into the semiconductor industry as a barrier layer film material to prevent the diffusion of copper atoms to silicon wafers. Copper does not form a compound with tantalum and nitrogen, so tantalum and tantalum base films are used as a barrier layer to prevent the diffusion of copper. In order to prevent copper atoms from diffusing into silicon matrix, tantalum nitride, tantalum silicide, tantalum carbide, tantalum nitride silicide, tantalum nitride carbide, and other tantalum base films are used as barrier layers with good effects.

Tantalum-based films have high conductivity, high thermal stability, and excellent corrosion resistance, which are highly resistant to foreign atoms.

Tantalum
Tantalum in Semiconductor Chips

Memory device

Tantalum oxide based resistance variable memory (RRAM) has the advantages of simple structure, fast reading and writing speed, strong miniaturization and compatibility with the CMOS process. Tantalum oxide material has good thermal stability that can reach 1100 ℃. There are only two stable phases between the tantalum and oxygen, namely Ta2O5 and TaO2, which also have two very high oxygen capacity ratio under the high temperature of 1000 ℃.

Passive device

When tantalum nitride film is exposed to air, an oxide layer will naturally form on the surface to protect the film from erosion in the presence of water vapor and voltage. Tantalum nitride chip resistors do not cause catastrophic failure of the device due to poor package or protective coating integrity.

At present, the application field of capacitor grade tantalum wire is further expanded with the rapid development of the electronic market. However, the development of tantalum capacitors has been greatly restricted due to various reasons, such as the increase in production cost, the further consumption of resources, and the intensified competition among ceramic capacitors.

Please visit http://www.samaterials.com for more information.

Why is Tantalum Widely Used in Electronic Industry?

Since the 1950s, TZM alloy (Mo-0.5 Ti-0.1 Zr-0.02 C) has been developed to meet the needs of the nuclear power system, aviation, and aerospace industry. It is the most widely used molybdenum alloy in the industry and the earliest refractory alloy used as a high-temperature structural material. However, the low-temperature brittleness of molybdenum alloy greatly limits its application.

tantalum metal

Tantalum metal has a lower plastic brittle transition temperature (196 ℃) and has better performance on the workability, weldability, ductility, and oxidation resistance at room temperature than that of molybdenum and tungsten in refractory metals. In addition, tantalum and its alloys with high melting point (2996 ℃), corrosion resistance, excellent high-temperature strength, and free of radioactive, etc, are widely used in the electronics industry, chemical industry, aerospace, weapon system, and the medical field, etc.

Tantalum metal
Tantalum metal

The applications of tantalum materials in the electronics industry mainly include tantalum capacitors, integrated circuits, electron tubes, memory devices, and passive devices.

Tantalum capacitor

Tantalum has the metal property of a valve, and the compact oxide film formed on its surface has unidirectional conductivity, which is suitable for making capacitors. Tantalum capacitors have a large capacity and small volume, and their capacitance is three times that of aluminum capacitors, but their volume is much smaller than that of aluminum capacitors. The working temperature of the tantalum capacitor ranges from -80 to 200 ℃, which can meet the demand of different temperatures. Besides, tantalum capacitors have strong stability and heat resistance performance and become a kind of material with high reliability in the electronics industry, which is widely used in military and high-tech fields that need to ensure high reliability.

Tantalum capacitor
Tantalum capacitor

Integrated circuit

Tantalum material is introduced into the semiconductor industry as a barrier layer thin-film material used to prevent the diffusion of copper atoms to silicon wafers. There are no compounds are formed between copper and tantalum, and copper and nitride, so tantalum and tantalum base membranes are used as barrier layers to prevent copper diffusion, and the typical thickness of the barrier layer is 0.005 ~ 0.01μm. In order to prevent the diffusion of copper atoms into the silicon matrix, tantalum nitride, tantalum silicide, tantalum carbide, and silicon nitride are used as barrier layers.

Memory device

Tantalum oxide matrix resistive memory (RRAM) has the advantages of simple structure, fast read and write speed, strong instability, and compatibility with the CMOS process. The permittivity of tantalum oxide material is very high, which is about 25. Moreover, there are only two stable phases between ta-O, Ta2O5 and TaO2, which have high oxygen capacity ratio under the high temperature of 1000 ℃.

Passive device

When tantalum nitride film is exposed to air, the surface will naturally form a layer of the oxide layer to protect the film from erosion in the presence of water vapor and voltage. The chip resistance of tantalum nitride will not cause catastrophic failure of the device due to the poor integrity of the package or protective coating.

RRAM
RRAM

When researchers discovered tantalum’s high-temperature resistance, good ductility, and corrosion resistance, the research on tantalum metal began. At present, the application field of capacitor grade tantalum wire is further expanded with the rapid development of the electronic market. However, the development of tantalum capacitors is greatly restricted due to various reasons, such as the increase in production cost, the further consumption of resources, and the intensification of the competition between ceramic and other capacitors.

In recent years, the market consumption of capacitor tantalum wire has been maintained at about 160 tons per year. With the development and use of military capacitors and the miniaturization and chip type of capacitors, the capacitor-grade tantalum wire gradually develops toward the thick and thin poles.

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Overview of the Metal Tantalum

Tantalum is a kind of refractory nonferrous metal with a hardness of 6-6.5. Its melting point can reach 2996 ℃, which is second only to tungsten and rhenium. Tantalum is malleable and can be drawn into thin foil, and it has a very small coefficient of thermal expansion, which is only 0.6 percent for every degree rise.

metal tantalum

Tantalum also has excellent chemical properties and is highly resistant to corrosion. Tantalum does not react with hydrochloric acid, concentrated nitric acid, and aqua regia under both cold and hot conditions. The experiments showed that tantalum did not react with the alkali solution, chlorine gas, bromine water, dilute sulfuric acid, and many other agents at room temperature, but only with hydrofluoric acid and hot concentrated sulfuric acid, which is relatively rare in metals.

Tantalum

Tantalum has a wide range of applications due to its excellent performance. For example, tantalum can be used as a substitute for stainless steel in the production of various inorganic acids. Besides that, tantalum can replace tasks that used to be undertaken by precious metal platinum in chemical, electronic, electrical, and other industries, thus greatly reducing the cost. Tantalum is manufactured into capacitor equipment for military use, and half of the world’s production of tantalum is used in tantalum capacitors. America’s military industry is unusually advanced, and it is the world’s largest arms exporter. The Defense Logistics Agency, the largest owner of tantalum, once bought a third of the world’s tantalum powder.

Tantalum is a kind of stable anodic oxide film in the acidic electrolyte. The electrolytic capacitor made of tantalum has the advantages of large capacity, small volume, and good reliability. Capacitor making is the most important use of tantalum, and the consumption of tantalum accounts for more than 2/3 at the end of the 1970s. Tantalum is also used to make electronic transmitter tubes and high-power tube parts. Moreover, Tantalum metal can be used as the structure of the combustor of the aircraft engine.

Tantalum and its alloys are widely used in all walks of life. Tantalum and tantalum-hafnium alloys are often used as heat-resistant, high-strength materials for rockets, missiles, and jet engines, as well as components for control and adjustment equipment. Tantalum is easy to be processed and shaped, so it is used as supporting accessories, heat shield, heater, and radiator in the high-temperature vacuum furnace. Tantalum carbide is used to make cemented carbide.

Boride, silicified, and nitride alloys of tantalum are used as heat release elements and liquid metal sheathing materials in the nuclear industry. Tantalum oxide is used in the manufacture of advanced optical glass and catalysts. In 1981, tantalum was consumed by about 73% of electronic components, 19% of the machinery industry, 6% of transportation, and 2% of the rest.

Stanford Advanced Materials supplies high-quality tantalum products to meet our customers’ R&D and production needs. Please visit http://www.samaterials.com for more information.