Contents:
Preparation
General Properties
General Suggested Uses
Parts Fabrication
Availability and Ordering Information
Sulfide Applications
Typical Properties of Sulfides

SULFIDES

Introduction
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
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

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

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General Properties

• 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.

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General Suggested Uses

• 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.

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Parts Fabrication
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.

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Availability and Ordering Information
CERAC 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.

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Sulfide Applications

Table 1: Sulfide Applications

Application	Typical Sulfides	Forms Used
Batteries	Lithium Cobalt Iron Nickel	Powders
Phosphor Ingredients	Strontium Zinc Cadmium	Powders
Lubricants and Lubricant Addditives	Molybdenum Niobium Copper Tantalum	Aerosol Cans Sputtering Targets Powders
Pigments	Cadmium Cerium Copper	Powders
Ceramic Coatings	Cobalt	Powders
Photovoltaic Materials	Cadmium	Powders Sputtering Targets
Industrial	Strontium	Powders
Infrared Filters	Antimony Cadmium	Evaporation Materials Sputtering Targets

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

Table 1 provides a glimpse of some of the recognized sulfide applications and the type of CERAC 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.

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.

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Table 2: Typical Properties of Sulfides

Sulfide Of	Formula	Color	Theo. Density, g/cm3	Melting Point, °C	Crystal Form
Aluminum	Al2S3	yellow-off white	2.55	1100	hexagonal
Antimony	Sb2S3	black	4.63	550	orthorhombic
Arsenic	As2S3	yellow or red	3.52	325	monoclinic
Barium	BaS	grey-white	4.33	2200*	cubic
Beryllium	BeS	grey-white	2.47	2200*	cubic
Bismuth	Bi2S3	brown-black	6.81	685	orthorhombic
Boron	B2S3	white	1.55	310	monoclinic
Cadmium	CdS	yellow-red	4.82	1750	hexagonal
Calcium	CaS	white-pink	2.61	72000	cubic
Cerium	CeS	gold	5.93	2450	cubic
Cerium	Ce2S3	red	5.2	1890	orthorhombic
Cerium	Ce2O2S	yellow	6.11	1950	hexagonal
Chromium	Cr2S3	brown-black	3.92	1550	hexagonal
Cobalt	CoS	black	5.83	1210	hexagonal
Cobalt	CoS2	black	4.8	-	cubic
Copper	Cu2S	black	5.97	1100	orthorhombic
Copper	CuS	black	4.68	200 decomp.	hexagonal
Dysprosium	Dy2S3	red-brown	6.55	1480	orthorhombic
Erbium	Er2S3	yellow	6.21	1730	monoclinic
Europium	EuS	black	5.74	-	cubic
Gadolinium	Gd2S3	red-brown	6.19	1885	orthorhombic
Gallium	Ga2S3	white	3.5	1250	cubic
Germanium	GeS	black	4.24	530	orthorhombic
Germanium	GeS2	white	3.03	800	orthorhombic
Hafnium	HfS2	red-brown	6.03	-	hexagonal
Holmium	Ho2S3	yellow	6.07	-	monoclinic
Indium	In2S	yellow-black	5.87	655	no system
Indium	InS	red-brown	5.18	695	orthorhombic
Indium	In2S3	orange	4.65	1050	cubic
Iron	FeS	black-brown	4.84	1190	hexagonal
Iron	FeS2	black	4.87	425 decomp	cubic
Lanthanum	La2S3	yellow	4.91	2150	no system
Lanthanum	LaS2	yellow-brown	4.9	1650	cubic
Lanthanum	La2O2S	white	5.75	1980	hexagonal
Lead	PbS	black	7.5	1115	cubic
Lithium	Li2S	white	1.63	975	cubic
Lutetium	Lu2S3	light grey	6.26	-	rhombohedral
Magnesium	MgS	white	2.86	2000	cubic
Manganese	MnS	green	3.99	1615	cubic
Mercury	HgS	black	8.1	1450	hexagonal
Molybdenum	MoS2	black	4.8	1815	hexagonal
Neodymium	Nd2S3	green	5.49	-	orthorhombic
Nickel	NiS	black	5.41	795	hexagonal
Niobium	NbS1.75	blue-black	4.58	-	hexagonal
Potassium	K2S	yellow	1.84	840	cubic
Praseodymium	Pr2S3	brown	5.31	1795	orthorhombic
Rhenium	Re2S7-H2O	black	4.87		tetragonal
Samarium	Sm2S3	red-brown	5.84	1900	orthorhombic
Scandium	Sc2S3	yellow	2.93	1775	cubic
Silicon	SiS2	white	2.06	sublimes	orthorhombic
Silver	Ag2S	black	7.27	825	monoclinic
Sodium	Na2S	white	1.89	1180	cubic
Strontium	SrS	pink	3.67	2000*	cubic
Terbium	Tb2S3	red	6.35	-	orthorhombic
Tantalum	TaS2	black	6.91	1300*	hexagonal
Thallium	Tl2S	blue-black	8.39	260	hexagonal
Thorium	ThS2	brown-black	7.36	2000*	orthorhombic
Thulium	Tm2S3	yellow-green	6.34	-	monoclinic
Tin	SnS	grey-black	5.08	882 decomp.	orthorhombic
Tin	SnS2	yellow	4.5	882	orthorhombic
Titanium	TiS2	gold	3.28	2000*	hexagonal
Tungsten	WS2	metallic-blue-grey	7.73	1130	hexagonal
Uranium	US2	grey-black	4.7	1850	tetragonal
Vanadium	V2S3	black	4.7	1930	no system
Ytterbium	Yb2S3	yellow	6.07	-	hexagonal
Yttrium	Y2S3	yellow	3.86	1600	monoclinic
Yttrium	Y2O2S	grey-white	4.92	2120	hexagonal
Zinc	ZnS	white or yellow	4.1	1850	cubic
Zirconium	ZrS2	brown	3.82	1550	hexagonal

# 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

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

Phone:  414-289-9800 /  FAX: 414-289-9805  /   ceracinfo@beminc.com