Gallium Refining: Processes, Purity Grades, and Supply Chain Geography (2026)

Gallium Refining at a Glance

What Is the Gallium Refining Process?

Gallium refining is a multi-stage purification sequence that takes crude metal at 98-99% purity from primary extraction and progressively removes impurities to reach 4N (99.99%), 5N (99.999%), or 6N (99.9999%) purity for semiconductor applications. The four core stages are hydrochemical processing, vacuum refining, electrorefining, and zone refining. Not every producer runs all four stages - the process path chosen depends on the target purity grade and the impurity profile of the crude feedstock.

What Are the Four Main Stages of Gallium Refining?

The four stages are: (1) hydrochemical processing using acid treatment to remove oxide inclusions and bulk impurities; (2) vacuum refining to remove volatile impurities such as zinc, cadmium, and mercury; (3) electrorefining in NaOH electrolyte to reach 5N-6N purity; and (4) zone refining using RF induction heating to push material beyond 6N toward 7N or higher for the most demanding semiconductor applications.

Refining Stage Summary

How Does Zone Refining Work for Gallium?

Zone refining exploits the physical principle that impurities in gallium have segregation coefficients below 1.0 - meaning impurities preferentially dissolve in the liquid phase rather than the solid phase as gallium crystallizes. An RF induction coil creates a narrow molten zone that is moved slowly along a gallium ingot at approximately 7.3 mm/h. As the zone travels, impurities are swept toward one end of the ingot, concentrating there while the bulk material behind it becomes progressively purer. After 18 passes, impurity levels can fall from 9,040 ppb to 460 ppb - a 95% reduction.

Zone Refining Parameters

How Does Electrorefining Work for Gallium?

Electrorefining uses a 5-20% sodium hydroxide (NaOH) electrolyte solution in which crude 4N gallium acts as the sacrificial anode and a platinum sheet serves as the cathode. When current passes through the cell at 0.05-1 A/cm² anode current density and 30-50°C, gallium selectively dissolves at the anode and plates onto the cathode at high purity. Metals less noble than gallium do not plate at the applied voltage; metals more noble than gallium do not dissolve from the anode. This electrochemical selectivity removes iron, copper, lead, residual zinc, and indium in a single step, producing 5N-6N output.

Electrorefining Process Parameters

What Is Solvent Extraction and How Is It Used in Gallium Refining?

Solvent extraction is the primary method for separating gallium from the Bayer process liquor or zinc smelting leachate at the crude recovery stage - before electrorefining or zone refining. It operates as a two-stage liquid-liquid extraction. Stage 1 uses a mixture of Kelex 100 (chelating agent) and Versatic-10 in kerosene to selectively pull gallium from the bulk solution, achieving over 90% gallium recovery within 2 minutes. Stage 2 uses Aliquat 336 (quaternary ammonium salt) with ascorbic acid to suppress iron extraction, removing ~85% of iron in the organic phase and precipitating the remainder during stripping.

Solvent Extraction: Two-Stage Configuration

What Are the Purity Grades of Gallium and What Are the Impurity Limits?

Gallium is sold in four commercial purity grades: 4N (99.99%), 5N (99.999%), 6N (99.9999%), and 7N (99.99999%). Each grade defines a maximum total impurity level and specific element limits. The step from 4N to 6N represents a 100-fold reduction in total impurities - from 100 ppm to 1 ppm. Zinc, indium, iron, lead, and copper are the most common problematic impurities; indium and zinc are the hardest to remove due to their chemical similarity to gallium.

Purity Grade Specifications

Hardest Impurities to Remove

How Is Purity Verified in High-Grade Gallium?

Three analytical methods are used in gallium quality control: ICP-OES (inductively coupled plasma optical emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), and GDMS (glow discharge mass spectrometry). For 4N-5N material, ICP-OES is standard at 1-10 ppb detection limits. For 6N+ material, GDMS is preferred because it directly analyzes the solid metal without dissolution, detecting impurities that dissolve into acids and become invisible to solution-based techniques - a critical distinction at sub-ppm levels.

Analytical Method Comparison

What Purity Does Each Semiconductor Application Require?

GaN power semiconductor and RF device production requires 7N (99.99999%) gallium as the preferred standard; GaAs wafer production for optoelectronics requires 6N (99.9999%) minimum; MOCVD epitaxy for LED and laser production requires 7N feedstock for the trimethylgallium (TMGa) precursor synthesis; and industrial applications use 4N-5N material. The step from 5N to 6N and from 6N to 7N each represents a 10-fold impurity reduction that requires progressively longer zone refining campaigns with diminishing throughput.

Purity Requirements by Application

Where Is Gallium Refining Geographically Concentrated?

Gallium refining is at least as concentrated in China as primary production, with China holding approximately 99% of global 6N+ refining capacity. Japan's Dowa Holdings is the leading non-Chinese high-purity refiner, holding the number one global position in high-purity gallium sales as of 2023, producing up to 6N material from zinc smelting by-products at Japanese facilities using imported Mexican zinc ore. The US has no active gallium refining of any grade. Europe's refining capacity is near zero since Germany ceased operations in 2016.

Global Refining Geography

What Is the Critical Gap in Western Gallium Refining Capacity?

Western government programs target crude gallium recovery and 4N-5N production, but the semiconductor industry needs 6N-7N refined gallium. The TRACE-Ga program ($6 million, DOE) targets 1 tonne/year prototype capacity at 4N-5N purity. The Metlen project (Greece) produces crude gallium at approximately 99-99.5% purity - below 4N - suitable for further refining but not for semiconductor use. Even if both programs succeed on schedule, no Western refinery will produce 6N gallium in meaningful volume before 2030 at the earliest.

Western Refining Program Gap Analysis

How Long Does It Take and What Does It Cost to Build a Gallium Refinery?

A dedicated gallium refinery capable of 100+ tonnes per year output requires an estimated 18-24 months to design and build, and a footprint of approximately 500-1,000 square meters for the core processing equipment. Specific capital cost data is not publicly disclosed by operating producers. The energy cost hierarchy from highest to lowest is: zone refining > electrorefining > vacuum refining > solvent extraction.

Refinery Construction Parameters (Estimates)

How Does Chinese Refining Capacity Compare to Global Demand?

China's high-purity gallium production capacity of approximately 340,000 kg/year at full utilization exceeds current global demand by a meaningful margin. Chinese domestic consumption runs approximately 630 tonnes per year, with export controls since August 2023 cutting exports from approximately 7,000 kg/month (pre-ban) to near zero for most of 2024-2025. The resulting Western price premium reflects not a global gallium shortage but a market split caused by export policy - with Chinese producers accumulating inventory while Western fabs pay scarcity prices.

Global Supply-Demand Balance (2024-2025)