Gadolinium (Gd)

Description

Basic Information

• Element Name: Gadolinium

• Symbol: Gd

• Atomic Number: 64

• Atomic Weight: 157.25

• Element Category: Lanthanide (Rare Earth Element)

• Standard State: Solid

• Appearance: Silvery-white, soft, ductile metal

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Chemical and Physical Properties

• Density: 7.90 g/cm³

• Melting Point: 1,312 °C (2,394 °F)

• Boiling Point: 3,273 °C (5,923 °F)

• Electronegativity (Pauling scale): 1.20

• Oxidation State: +3 (dominant)

• Magnetism: Ferromagnetic below 20°C; Paramagnetic above that

• Special Feature: Displays strong neutron absorption and magnetic susceptibility

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Reactivity and Storage

Gadolinium reacts slowly with air and water but forms a protective oxide layer, enhancing corrosion resistance. It dissolves readily in dilute acids. For storage, it is typically kept in sealed containers or under inert gas to prevent further oxidation.

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Occurrence and Extraction

Gadolinium is found in rare earth minerals such as monazite and bastnäsite, and is usually extracted as a byproduct of refining other heavy rare earths. Separation is achieved using solvent extraction and ion-exchange methods.

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Isotopes

Natural gadolinium consists of seven stable isotopes, among which Gd-157 and Gd-155 are notable for their very high neutron absorption cross-sections, making them suitable for nuclear applications.

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Key Applications

1. Medical Imaging (MRI Contrast Agents)

• Gadolinium-based contrast agents (GBCAs) are used in magnetic resonance imaging (MRI)

  • Enhance visibility of soft tissues, tumors, and blood vessels

  • Widely used in hospitals and diagnostic imaging centers globally

• Gadolinium’s strong magnetic moment improves T1-weighted contrast significantly

2. Nuclear Reactor Shielding & Control

• Gadolinium is an effective neutron absorber due to Gd-157 and Gd-155

  • Used in nuclear reactor control rods, burnable absorbers, and shielding materials

  • Helps in regulating fission and protecting sensitive instruments

3. Magnetic Refrigeration Research

• Gadolinium exhibits a strong magnetocaloric effect

  • Undergoing temperature change when exposed to a magnetic field

  • Used in experimental magnetic refrigeration systems as an eco-friendly alternative to gas-compression refrigeration

4. Phosphors & Luminescent Materials

• Gd³⁺ ions are used in X-ray intensifying screens and LED phosphors

  • Enhance image brightness and resolution in radiographic systems

5. Alloys and Electronics

• Gadolinium is added to iron, chromium, and other alloys to improve workability, magnetism, and oxidation resistance

  • Used in aerospace components and microwave technology

6. Magnetic and Spintronic Devices

• Its magnetic properties make it valuable in spintronic research, data storage devices, and magneto-optic materials

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Strategic Importance

• Gadolinium is considered a strategic material due to its broad use in medical imaging, clean energy, and national defense

• Supply is mostly dependent on China, raising concerns about supply chain security for Western countries

• Recycling from MRI contrast waste and other rare earth waste streams is under development

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Interesting Facts

• Discovered in 1880 by Swiss chemist Jean Charles Galissard de Marignac

• Named after Finnish chemist Johan Gadolin, a pioneer in rare earth research

• Gadolinium is one of the few elements that are both ferromagnetic and highly paramagnetic, depending on temperature

• Plays a crucial role in modern medical diagnostics and neutron shielding technologies