HPA Markets and Uses

High Purity Alumina (HPA) – Mineral and Product Description

High purity alumina is a specialty product, differentiated from common alumina products by its substantially higher purity, market scarcity, cost, and application in technology products. The global market value is estimated at about US$1Bn in 2021.

HPA and smelter-grade alumina (SGA) are different products, designed for very different markets.

  • SGA (aluminum oxide), is refined from bauxite as feedstock for smelting aluminum metal.  The global SGA market value is about US$50Bn (price: US$400/tonne).
  • Some SGA refiners make higher grade specialty products, but they do not qualify as HPA.   

What qualifies as HPA?  The grade delineation on high purity HPA is 99.99+%, also identified as 4N+.  Higher grades, 5N or 6N, are offered and carry premium pricing over 4N.  Virtually all HPA is manufactured today by chemical companies, utilizing high purity, expensive aluminum metal as feedstock and a chemical process known as the alkoxide process.   This technique allows producers to consistently meet 4N+ grade spec, but at relatively high overall product cost.

At 4N grade, HPA has under 100ppm of total impurities.  This product purity requirement is a manufacturing challenge, and thus supports significantly higher market pricing, at US$20-30/kg.  This premium pricing comes with strict adherence to quality, micro-sizing of particles, consistency of specified granularity, and often custom-designed specifications to suit individual customer requirements.    Lower grade 3N material sells at a >50% discount to 4N pricing, and is not acceptable purity for many of the technical market applications reserved for HPA. 

HPA Markets - Current Uses and Growth Opportunities

HPA product is demanded by various technology manufactures for unique characteristics in a number of areas, most notably electrical insulation properties (alumina is a non-conducting oxide), exceptional hardness and strength, and a combination of both high thermal stability and efficient thermal conductivity.

The largest current market for HPA today is in specific components that make up light-emitting diode (LED) style lighting.  HPA is used as a smooth, thermal and electrically resistant synthetic sapphire wafer substrate upon which the circuitry and diode systems are constructed.  HPA in powder form is an ingredient in both the phosphors and the diodes as well.  The quality requirement in this application is 4N or better, and there is no commercial identified substitute, after decades of application.  Asian markets dominate in LED manufacture, specifically China and Japan.

Certain smaller markets for HPA are important, based on their history of use and potential growth.  HPA can be processed into synthetic sapphire material for high quality lenses that are durable, scratch-resistant, and optically superior to more common glass forms.  This material is commonly used in watch lenses and increasingly in cell phone camera lenses and other personal electronic devices.  Many forms of higher quality glass commonly include additions of 5-10% HPA.

The emerging and very large potential growth market for HPA is in lithium-ion batteries (LiB’s).  The current application for 4N product is in a battery separator, as a ceramic coating on an inorganic polyvinyl insulating membrane placed between the battery anode and cathode.

This HPA/ceramic coating serves to provide a number of critical functions, specifically:

  • It contributes to the electrical insulation function central to the separator’s purpose.
  • It provides both physical support and penetration protection from dendrites that can form in the gel electrolyte on either side of the separator.
  • It greatly improves the thermal resistance of the membrane separator, allowing for higher internal battery temperatures and supporting higher battery power density designs. 
  • It performs these functions while not impeding the movement of lithium ions through the membrane on which it is coated, during repeated charge and discharge cycles.

Because HPA has been found to perform these functions effectively and economically, it has been applied for this purpose in most LiB’s for more than a decade.

HPA also has potential for use in next-gen configurations for anodes, cathodes and solid electrolyte systems, where extensive research continues today.  As a part of this technological effort to improve performance in every component of a LiB, the design of today’s separator is likely to benefit as well.   The role of HPA, as a proven performance and safety enhancing component in today’s separators argues for continued application in those future designs.

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