Sulfides

Sulfides

Sulfides Overview

Inorganic sulfides are compounds of various metals with sulfur. Sulfides are generally not thought of as high temperature materials, but at least 30 metallic sulfides display refractory properties which indicate potential uses at elevated temperatures. Some of the refractory sulfides are more stable than oxides in vacuum, giving rise to interesting potential applications.

Preparation of Sulfides

Sulfides generally are prepared by any of six preparative schemes:

1. Direct reaction of the elements.
   Be + S BeS
2. Reaction of metal oxides or carbonates with a sulfur compound.
   CaO + H₂S CaS + H₂O
   Li₂CO₃ + H₂S Li₂S + CO₂ + H₂O
3. Reduction of a higher sulfide.
   2Ce₂S₃ + 2CeH₃ 6CeS + 3H₂
4. Reaction of a metal hydride with a sulfur compound.
   2UH₃ + 4H₂S 2US₂ + 7H₂
5. Reduction of metallic sulfates.
   BaSO₄ + 4C BaS + 4CO
6. Reaction of a metallic halide with a sulfur compound.
   2LaCl₃ + 3H₂S La₂S₃ + 6HCl

Materion Advanced Chemicals employs all of these routes, plus proprietary developments, to prepare the one of the largest families of pure or mixed sulfides available.

General Properties of Sulfides

• Many sulfides have melting points above those of oxides.
• Sulfides can either be salt-like (e.g., the alkaline earth sulfides) or hard-metal like (e.g., the refractory sulfides).
• Sulfides are generally hydrolyzed by water.
• Sulfides generally oxidize readily in moist air at ambient temperature or in dry air at elevated temperature.
• Some sulfides possess semi-metallic character and have potentially valuable electronic properties.

General Suggested Uses for Sulfides

• Tantalum and niobium sulfides have low friction coefficients and can be used as lubricants for optical and sensitive instruments.
• Rare earth sulfides are semi-conductors and have been used in thermoelectric devices.
• Alkaline earth sulfides plus those of calcium and zinc are used for phosphor compositions.
• Molybdenum and tungsten sulfides are widely used, non-graphitic commercial lubricants.

Fabrication of Sulfides

Numerous sulfides can be fabricated by various techniques (e.g., hot-pressing, isostatic pressing) without added binders to form dense bodies. Please contact the CERAC sales department for more information.

Availability and Ordering Information of Sulfides

Materion Advanced Chemicals prepares a comprehensive selection of sulfides. Small lots are promptly available from stock for experimental or test purposes. Production quantities of many sulfides are also available from stock. Large amounts of other sulfides are produced to customer's specification for rapid shipment. Mixed sulfides (e.g., Li₂S-FeS₂), non-stoichiometric compositions or special purities and particle sizes can be custom manufactured. Please contact our sales department with your exact specifications.

Applications of Sulfides

Table 1: Sulfide Applications

Materion Advanced Chemicals Applications

The wide variety of Materion Advanced Chemicals sulfides available has resulted from the numerous and largely unrelated applications for these products. In many individual applications and with many individual customers, Materion Advanced Chemicals has developed products specifically for existing or new applications. In fact, Materion Advanced Chemicals’ product line has grown largely in response to customer requirements. Materion Advanced Chemicals highly values these customer relationships and encourages any and all questions, comments and suggestions related to the performance of Materion Advanced Chemicals sulfides in specific applications.

Table 1 provides a glimpse of some of the recognized sulfide applications and the type of Materion Advanced Chemicals products suitable for use in each case. For example, phosphor, battery and pigment applications usually require fine powders while numerous thin film applications require the use of sputtering targets or evaporation materials.

The scope of sulfide applications is continually changing and evolving. While zinc and cadmium sulfides have a lengthy history of use in cathode ray tubes, strontium sulfide has only recently become of importance in conversion of infrared radiation to visible light. Also, various sulfides have come under recent scrutiny as new battery materials, largely due to the relatively stable forms of metal sulfides in multiple oxidation states and to environmental acceptabilities. These battery developments extend from specialized military and industrial uses to evaluations directed toward the propulsion of electric vehicles.

Sulfide Applications

In summary, present and future sulfide applications are derived mainly from the diverse properties exhibited by this family of products. For example, many sulfides exhibit semimetallic behavior, giving rise to electronic applications. Some are highly refractory, with melting points exceeding those of oxides, and are stable during thin film formation by vacuum deposition. Others have crystal structures and very high lubricities.

Table 2: Typical Properties of Sulfides

# The data listed are selected from reliable literature and are only indicative. No guarantees of accuracy are implied

* Melting points are much higher than listed, but no accurate measurements have been made.

- Indicates data not available

Note: Facts pertaining to properties and processing parameters of sulfides were derived from published literature sources. Although this information is believed to be correct, Materion Advanced Chemicals does not guarantee its accuracy.

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