- Cadmium molybdate (CdMoO₄) is an inorganic compound composed of cadmium cations (Cd²⁺) and molybdate anions (MoO₄²⁻) arranged in a scheelite-type tetragonal crystal structure.
- It typically appears as a pale yellow, white, or colorless crystalline solid, with a density around 5.0–5.1 g/cm³ and a melting point near 1040 °C before decomposition.
- The material is insoluble in water but dissolves in strong acids, releasing toxic cadmium ions.
- In its structure, each molybdenum atom is tetrahedrally coordinated by oxygen atoms, while cadmium atoms are coordinated by eight oxygen atoms in a more irregular geometry. Bonding within CdMoO₄ is mixed ionic–covalent, with covalent Mo–O bonds and more ionic Cd–O interactions, a combination that influences both optical and mechanical properties.
- The compound exhibits notable photoluminescence when excited by ultraviolet light, emitting in the visible range due to electronic transitions within the molybdate group. Its optical characteristics can be tuned by doping with rare-earth ions such as europium, terbium, or dysprosium, allowing modification of the emission color and intensity. The material’s wide band gap, around 3.2–3.4 eV, makes it suitable as a host lattice for luminescent centers and also allows photocatalytic activity under UV irradiation. These properties have led to its investigation for phosphors in lighting and display technologies, scintillation materials for radiation detection, and catalysts for the degradation of organic pollutants.
- Cadmium molybdate can be prepared by heating stoichiometric mixtures of cadmium oxide or carbonate with molybdenum trioxide in the solid state, by co-precipitating aqueous solutions of cadmium salts with ammonium molybdate followed by calcination, or by hydrothermal and sol–gel methods to obtain fine, highly crystalline powders. Its applications extend into optoelectronics, where it can serve as a phosphor host; photocatalysis, where it aids in the breakdown of dyes; and analytical chemistry, where molybdate-based reactivity is useful. Historically, it has also been used as a pigment, though such uses have largely ceased due to cadmium’s toxicity.
- Handling cadmium molybdate requires stringent safety measures, as cadmium compounds are highly toxic and carcinogenic, causing kidney damage, bone demineralization, and lung injury upon exposure. While molybdenum compounds are generally less harmful, they can still disrupt biological processes in excess. All work with CdMoO₄ must be performed in controlled environments with protective equipment, and waste must be disposed of as hazardous material to prevent environmental contamination.
- Recent research has focused on nanostructured CdMoO₄ and hybrid composites to enhance photocatalytic efficiency and luminescence, but increasing regulatory pressure is driving the search for less hazardous alternatives for widespread applications.
