Сульфид кальция и лантана (CaLa2S4)

Identification

Calcium Lanthanum Sulfide (CaLa2S4) is a mixed inorganic calcium and lanthanum sulfide, CAS number 12525-03-0. The chemical composition is described by the elements Ca, La, S. The English name is Calcium lanthanum sulfide (CaLa2S4). Synonyms: Calcium lanthanum sulfide (CaLa2S4); Lanthanate (1-), dithioxo-, calcium (21).

The initial dump for the product in the data source is empty - numerical attributes (molecular weight, EU number, physical constants) for this position are not given in the database. All information below is collected from open scientific publications according to CAS 12525-03-0.

Crystal structure and composition

CaLa2S4 crystallizes in a cubic structure of the Th3P4 type and forms a solid solution with La2S3 (lanthanum sulfide), maintaining this cubic lattice. The molar ratio of CaS to La2S3 in the base composition is 50:50. The compound belongs to the class of mixed sulfides of rare earth and alkaline earth metals.

Optical properties

The substance is designed as a far-IR optical ceramic material with a bandwidth in the 8-14 µm atmospheric window, somewhat wider than that of zinc sulfide (ZnS). The band gap calculated from the modified Beckel-Johnson potential is 2.80 eV, which is consistent with the experimental data. The refractive index and vibrational modes of the lattice are determined using the specular reflection method with the Kramers-Kronig transformation: analysis using factor group theory predicts five transverse optical modes, of which intense high-frequency modes at 142 and 205 cm⁻¹ are experimentally observed.

Mechanical and performance properties

CaLa2S4 is superior in hardness and refractoriness to zinc sulfide, although its coefficient of thermal expansion is noticeably higher. The resistance to erosion by raindrops of CaLa2S4 is significantly better than that of ZnS, which is important for external optical elements operating at speed and in precipitation.

Scope of application

• material for infrared windows and domes of optical-electronic systems in the range of 8-14 microns
• components of thermal imaging equipment and IR sensors in the medium and long wave range
• fairings of homing heads and external optical elements operating under mechanical and atmospheric load conditions
• object of research as polycrystalline ceramics to replace zinc sulfide where higher mechanical strength is required

Substance class

Mixed sulfide belongs to a family of ceramic materials based on rare earth sulfides, stabilized by the introduction of the alkaline earth calcium cation into the Th3P4 structure - such stabilization increases mechanical strength compared to pure lanthanum sulfide La2S3.

Storage and handling

Like other inorganic sulfides, the substance should be stored in a dry place, away from acids and oxidizing agents - contact of sulfides with strong acids can lead to the release of hydrogen sulfide. Handling the powder requires respiratory protection, since finely dispersed sulfide ceramics can generate dust when crushing and processing workpieces.