Alumina advances in technical ceramics

By IM Staff
Published: Friday, 18 March 2016

Alumina is the most widely used raw material in technical ceramics production, accounting for up to 80% of the total used. Jessica Roberts* looks at some of the key raw materials in advanced ceramics and their supply chains and outlines which sectors are poised for growth.

Technical (or advanced) ceramics is a fairly loose term and covers a large and varied group of materials. There is no strict definition of a technical ceramic, but it includes ceramics with superior mechanical, electrical, thermal, biological and chemical properties. Materials that are broadly accepted to come under the "technical ceramics" umbrella include wear-resistant ceramics, electronic components and electrical insulators, as well as ceramics used in coatings and automotive catalysts.

There are a number of raw materials used in advanced ceramics production, but alumina is the most important by volume, accounting for 70-80% of the materials used depending on whether it is in its purest form or mixed with other oxides (Figure 1). High-alumina ceramics provide high strength, hardness and resistance to impact, corrosion, abrasion and temperature and have excellent electrical isolation. Other important raw materials include zirconia, yttrium and rare earth oxides, silicon carbide, silicon nitride and boron carbide.

Figure 1: Materials used in
technical ceramics in 2014 (%)

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Source: Almatis

Technical ceramics raw materials

Alumina

Most alumina used in ceramics is produced via the Bayer process but small amounts of high purity material are produced by other routes, which may include the Bayer process in the early stages. Alkoxide, aluminium sulphate derivatives or hydrates made from 99.99% pure metal are also used. Powders derived from these sources are up to 10 times more expensive than Bayer-process alumina.

There is nearly 11m tpa non-metallurgical alumina (calcined and hydrate) capacity held globally, but only a small proportion of this material meets the specifications for use in advanced ceramics. The main producers of calcined alumina suitable for use in this application include Germany-headquartered companies Almatis, Martinswerk (which was acquired by US-based Huber Engineered Materials in December 2015) and Nabaltec as well as France-based Alteo, Japan’s Showa Denko, South Korean producer, KC Corp. and AluChem, which is based in the US. 

Leading producers of ultra high-purity alumina, which is used in some niche ceramics applications such as synthetic sapphire, include Hebei Pengda New Material (China), Baikowski (France and the USA), Sumitomo Chemical (Japan and South Korea) and Sasol (US). In addition, Australia-baed Altech Chemicals Ltd and Canada’s Orbite Technologies Inc. are developing ultra high-purity alumina projects which are expected to come online over the next few years.

Zirconia

Zirconia (ZrO2) is obtained by processing zircon (ZrSiO4) or baddeleyite (natural zirconia). Four process routes are currently used commercially to extract zirconia from zircon sand: chemical precipitation; alkaline; fused; and plasma methods. Material produced via each process can be used to make advanced ceramics, but chemical zirconia accounts for the highest proportion.

Zirconia ceramics are used for their conducting characteristics, for example in electronic sensors, or structural properties in a range of engineering applications, including wear parts, ceramic coatings and as high-strength and high-toughness ceramic components. The electrical uses of zirconia ceramics are well established, whereas structural applications are less developed but offer promising growth prospects for the zirconia market.  

China is the leading zirconia producer globally, with nearly 60% of total production capacity. The largest supplier in the world is Imerys Advanced Materials Yingkou, a subsidiary of Imerys Fused Minerals, itself a division of French industrial minerals group Imerys SA. Imerys Advanced Materials Yingkou is based in Liaoning, China. 

Other leading producers of zirconia suitable for use in advanced ceramics include Saint-Gobain (China, France and the US), Guangdong Orient Zirconic (China), Daiichi Kigenso Kagaku Kogyo (Japan), Tosoh (Japan), Nippon Denko (Japan), MEL Chemicals (UK and US), TAM Ceramics (US), Washington Mills Electro Minerals (UK and US), and Zircoa (US).

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Cut above: Advanced zirconia ceramics can be used to make kitchen tools,
such as zirconia oxide ceramic knives.  (Bill Smith, via Flickr)

Yttria and rare earth oxides

The main application for rare earths in advanced ceramics is yttrium oxide (yttria) as a stabiliser in yttria-stabilised zirconia (YSZ), for use in large number of applications, including thermal barrier coatings in industrial gas and aviation turbines; fibre-optic connectors; oxygen sensors for automotive fuel control; fuel cell components; and dental and other biomedical applications. Yttrium oxide can be substituted with other stabilisers such as calcia or magnesia, but the substitutes generally impart lower toughness.

Yttrium is also used as a sintering agent in the production of silicon nitride materials for high-temperature/endurance applications such as gas turbines, automotive engine parts, bearings and machine tools. Meanwhile, neodymium oxide is used as a component in precious metal ceramic capacitors for electrical applications. Cerium, lanthanum and praseodymium also have some applications in advanced ceramics, but by far the most widely used rare earth oxide (REO) is yttria, at over 60% of the REO total in this market. In addition, yttria is used in certain grades of silicon aluminium oxynitrides (SiAlONs). 

China is the world’s largest producer of REOs at nearly 90% of the total and is the largest consumer of the minerals in ceramics applications. The leading producers in China include Baogang Group, Aluminium Corp. of China (Chinalco) and Ganzhou Mining.

Advanced ceramic producers

Most consumption of raw materials for advanced ceramics production takes place in Europe, North America and Asia, where the major manufacturers are located. 

CeramTec of Germany, which was acquired by the European private equity firm Cinven in August 2013 for €1.49bn ($166bn**), is one of the leading producers. CeramTec was formerly part of US-based chemicals producer Rockwood Holdings, but was divested when Rockwood (itself later acquired by Albemarle Corp.) refocused on its lithium activities. The bulk of the company’s production takes place in Germany, but CeramTec also has plants in the US and China. CeramTec has a current portfolio of over 10,000 different products, components and parts made of advanced ceramics and ceramic materials.

US-headquartered CoorsTek has technical ceramics plants in Europe and Asia as well as in North America. The company manufactures ceramic components for defence, medical, automotive, semiconductor, aerospace, electronics, power generation, telecommunications and other high-technology applications. It has increased its capabilities following a series of expansions and purchases since 2007, including the acquisition of most of Saint-Gobain’s advanced technical ceramics facilities for $245m in 2010, the technical ceramics division of BAE Systems in 2011 and UK-based technical ceramics producer Dynamic-Ceramic in 2013.

Kyocera of Japan is a leading producer of ceramic components for various applications, including cutting tools, ceramic and sapphire substrates, medical materials, ceramic packages for light emitting diodes (LEDs), kitchen tools and substrates for high-resolution print heads.

Morgan Technical Ceramics is a subsidiary of UK-based Morgan Advanced Materials (formerly Morgan Crucible Co.), and produces a range of structural ceramic components, ceramic coatings, piezo ceramic components, sensors, ceramic cores, capacitors and other products. Morgan Advanced Materials operates from a number of plants globally, including North America, Europe, South America, Oceania, Asia and the Middle East.

Germany-headquartered Lapp Insulators is a leading producer of high-voltage insulators. The company was headquartered in the US until its acquisition in August 2011 by Quadriga Capital. In October 2015, Lapp was purchased by the PFISTERER Group, a supplier and systems provider for energy infrastructure. High-voltage insulators are produced in Germany, the US, China, Romania and Poland.

Market applications

Applications for technical ceramic products can be broadly divided into structural ceramics and functional ceramics. Structural ceramics are prized for their mechanical properties, including high strength, toughness, hardness and creep resistance. These materials must be very hard, dimensionally stable and strong. Depending on the application, these ceramics must also maintain these properties at high temperatures.

Within the structural ceramics market there are a number of products and applications. The main markets by volume are grinding media, ceramic rollers, catalytic substrates and chemical processing. Grinding media are the single largest application in wear-resistant ceramics by volume, accounting for over a third of the sector. Lower volume but higher value applications include synthetic sapphire, ceramic coatings, bioceramics, ceramic armour and cutting tools.

Functional ceramics are prized for their superior electric, magnetic and optical properties. The main applications for functional ceramics include electronics, high-voltage insulators and spark plugs. Advanced ceramics are used in electronic substrates, microchips, pressure sensors, piezoelectrics, resistors and inductor bodies. 

In terms of raw materials, very high purity aluminas are widely used and, because of this, the market for electronic substrates is the largest by value for technical ceramics. Increasing sophistication of electronic components has led to growing use of purer, and therefore more effective, aluminas in order to insulate components from the waste heat generated.

Over the next five years, structural ceramics are expected to show the highest growth rates within the technical ceramics sector – growing in line with the forecast global GDP rate of 3.3% per annum. 

The main market driver behind structural ceramics is the grinding media segment, which is forecast to grow slightly under the market average. Catalytic substrates, chemical processing aids and ceramic coatings are all expected to grow in excess of the GDP forecast out to 2021. 

However, by far the highest growth rate for structural ceramics is forecast to be in synthetic sapphire production, which Roskill projects will grow by 15%py over the next five years. This is due to the use of synthetic sapphire substrates in the LED lighting market. If sapphire finds a large role in the smartphone sector – for instance in screens – then demand growth could be much higher than this.

Growth in the functional ceramics sector is likely to be below that of structural ceramics, as one of the largest applications – high-voltage insulators – is forecast to decline out to 2021. This is because ceramic-based high voltage (HV) insulators have come under increasing competition from glass and polymer-based insulators, which offer equivalent mechanical properties at a lower weight. Electronic ceramics, meanwhile, are expected to grow well in excess of the global GDP forecast due to their link with the consumer electronics sector.

Sources: 

Non-Metallurgical Bauxite & Alumina: Global Industry, Markets & Outlook to 2021 (published February 2016), Rare Earths: Market Outlook to 2020 (March 2015), Zirconium Oxide, Chemicals & Metal: Global Industry & Markets (October 2014), Roskill Information Services.

*Jessica Roberts is a senior analyst at Roskill Information Services in the UK.

**Conversion made March 2016