Rare Earth is a group of 17 elements including 15 lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) located in the bottom of the Periodic Table from atomic number 57 to 71, and Sc numbered 21 and Y numbered 39. Scandium and yttrium are considered rare earth elements because they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties.Introduction to Rare Earth Elements
Rare earth elements (REEs) are a group of 17 elements that include the 15 lanthanides and two additional elements, scandium (Sc) and yttrium (Y). These elements are characterized by their unique electronic configurations and chemical properties.
Table: Classification of Rare Earth Elements
| Category | Elements |
|---|---|
| LREE | Sc, La, Ce, Pr, Nd |
| MREE | Sm, Eu, Gd, Y, Tb, Dy |
| HREE | Ho, Er, Tm, Yb, Lu |
Abbreviated Words in the Rare Earth Industry
Table: Common Abbreviations and Their Meanings
| Abbreviation | Full Form |
|---|---|
| RE | Rare Earth |
| REM | Rare Earth Metals |
| REE | Rare Earth Elements |
| REO | Rare Earth Oxides |
| REY | Rare Earth Elements and Yttrium |
| LREE | Light Rare Earth Elements |
| MREE | Medium Rare Earth Elements |
| HREE | Heavy Rare Earth Elements |
| TREO | Total Rare Earth Oxide |
| TREM | Total Rare Earth Metal |
| L. O. I. | Loss on Ignition |
Purity on Rare Earth Oxide Basis
Understanding REO Basis Purity
In the context of rare earth oxides and compounds, purity is often expressed relative to the total rare earth oxide content (TREO).
Example Calculation: If a sample has "CeO2 > 99%" on an REO basis, it means:
To find the absolute purity of a specific oxide within a material, use the formula
This method provides a clear understanding of how much of the specified oxide is present compared to all other rare earth oxides combined.
Purity on Rare Earth Metal Basis
Interpreting REM Basis Purity
For rare earth metals, purity is typically described based on the proportion of a particular metal relative to the total rare earth metals (TREM).
Example Interpretation: A statement like "Ce > 99%" on an REM basis translates to:
Absolute purity calculations follow a similar structure:
This approach ensures clarity when discussing the concentration of individual rare earth metals within a mixture or alloy.
Purity Calculations for Rare Earth Materials
Table: Purity Calculation Methods
| Basis | Formula | Example Interpretation |
|---|---|---|
| REO Basis | X 100% | "CeO2 > 99%" means " |
| REM Basis | X 100% | "Ce > 99%" means " |
This approach ensures clarity when discussing the concentration of individual rare earth metals within a mixture or alloy.
Applications of Rare Earth Elements
Often referred to as "industrial vitamins," REEs play crucial roles across various sectors:
- Permanent Magnets: Neodymium-iron-boron magnets, known for their high remanence, coercivity, and energy product, find extensive use in electronics, aerospace industries, and wind power generation.
- Catalysts: Rare earth molecular sieve catalysts enhance light oil yields during petroleum cracking while reducing pollutant emissions.
- Phosphors: Phosphor powders made from europium, terbium, etc., improve luminous efficiency and color rendering in lighting devices, displays, and lasers.
- Batteries: Lanthanide-based materials are key components in nickel-metal hydride batteries used in hybrid vehicles and consumer electronics.
- Steel Industry: Addition of rare earths enhances steel's strength, toughness, and corrosion resistance.
- Glass & Ceramics: Rare earth oxides contribute to high-quality optical glasses, specialty glasses, and ceramic glazes.
- Agriculture: Moderate application of rare earth elements promotes crop growth, increases yield and quality, and improves plant resilience against adverse conditions.
- Other Applications: REEs also feature prominently in digital products, green energy solutions, healthcare, transportation, among others.