Big Future for Titanium Compounds in Electronics
By Dr. Peter Harrop, IDTechEx
January 22, 2013
OEMs want to lessen the risk of their materials development programs involved with elements and compounds for electrical and electronic applications. To do this, design engineers need to understand which basic families of formulation will be most widely employed in next-generation electronics, from Nano Electromechanical Devices (NEMS) to completely re-invented large lithium-ion batteries in electric cars and consumer electronics and wide area, flexible solar cells. IDTechEx has examined this from the viewpoint of what high-value-added materials will be needed over the coming decade and which families of compounds are the most electronically versatile.
Many Applications for Titanium
There is good news for those skilled in the chemistry of titanium. Titanium compounds perform an ever-wider variety of electrical and electronic functions — far broader than silicon compounds, for instance. Titanium compounds can be piezoelectrics, even printed to become piezo energy harvesters and sensors. They can be dielectrics in capacitors and transistors, sensitized scaffolds turning light into electricity, electrically moved pigments, and superior anodes and cathodes in lithium-ion batteries intercalating lithium ions. For example, Toshiba, Altairnano, and Enerdel batteries have exceptional tolerance of fast charge and discharge in electric vehicles, thanks to lithium titanate anodes. Lithium manganese titanium spinel provides energy density when used by others in cathodes. For example, one patent reveals a method of making an effective spinel compound of formula Li4Ti5O12 for this purpose.
When modified to have a non-stoichiometric layer, titanium dioxide exhibits memristor action, mimicking the human brain. It remembers the current passed through. Titanium salts act as electrets, storing charge on the surface, and some can be micro-machined to perform the many electronic and electrical functions at nano scale. The compounds that are so useful include the oxide, lithium titanates, and complex metalloids with other metals in active electrodes of lithium-ion batteries, as well as supercabatteries (Asymmetric Electrochemical Double Layer Capacitors or AEDLC, notably lithium-ion capacitors). Barium titanate is another useful formulation, in this case seen as high-permittivity dielectric, such as in experimental printed field-effect transistors. There is also lead zirconate titanate, which is the archetypal piezoelectric. New forms of these often include inks used in electronics and for batteries, and some have even demonstrated in circuits printed on paper.
The hugely popular e-readers, such as the Amazon Kindle, read as easily as a newspaper, and their screens become even clearer in sunshine. This is in contrast to a laptop, tablet, or even a mobile phone, which use LCD or OLED displays. The e-readers’ electrophoretic displays move the same pigments used in newspapers (carbon for black and titanium dioxide for white). By contrast, a Dye Sensitized Solar Cell (DSSC) employs a titanium dioxide scaffold sensitized by a ruthenium-based dye to capture light and thus release electrons by a photo-electrochemical reaction, not the pn junction as used in all other forms of solar cells. The result is a flexible solar cell that works well with low levels of light; polarized light such as reflections off snow, water, or windows; and light at very narrow angles, as is typical in the Arctic/Antarctic regions.
Titanium Nitride and Supercapacitors
Titanium nitride may also have a place. Researchers at the University of Maryland and the Korea Advanced Institute of Science and Technology have developed an electrostatic capacitor with 10 billion nanoscale capacitors per square centimeter, giving it 250 times greater surface area than that of a conventional capacitor of comparable size. The misleadingly called Nano Supercapacitor (it is not an EDLC) was being developed primarily as part of a hybrid battery-capacitor system for electric cars but has not reached the market yet.
Current commercial supercapacitors range from 0.5 to 40 Wh/kg, yet it is thought they can reach 3,000 Wh/kg, a tenfold increase on even the best lithium-ion batteries in the laboratory today. For example, with this technology, the range of a pure electric car could reach 1,000 miles versus the 100 miles they max out at today. Each nanopore created in aluminium is 50 nanometers in diameter and up to 30 micrometers deep. Next, a sandwich of two layers of titanium nitride (TiN) metal separated by an insulation layer are deposited using Atomic Layer Deposition (ALD) into the pores topped with another layer of aluminum foil.
The versatility of inorganic titanium dioxide matches that of polyvinylidene difluoride (PVDF), the organic “gymnast” of electronic and electrical properties, though they rarely compete in device application. Both compounds are even used as fillers and binders in new electrical and electronic devices. They are certainly likely to be widely used in the new electronics we’ll see in the coming years.
Dr. Peter Harrop is chairman of IDTechEx.
This article is excerpted from the report Most-Needed Chemicals for New Disruptive Electronics and Electrics: De-risk Your Investment.