Zn2SiO4

Zn2SiO4, known as zinc orthosilicate, is a silicate compound best known in its mineral form as willemite. In addition to its natural occurrence, Zn2SiO4 serves as a host lattice for phosphors when doped with activator ions, and it has applications in ceramics and materials science.

The structure of Zn2SiO4 comprises Zn2+ cations coordinated to silicate (SiO4) tetrahedra. It exists in multiple crystallographic polymorphs, commonly referred to as α-Zn2SiO4 and β-Zn2SiO4, which differ in crystal structure and stability as temperature changes. These polymorphs reflect distinct packing arrangements of the zinc and silicate framework.

Willemite occurs in hydrothermal veins and oxidized zinc ore deposits. Notable localities include the Franklin mining district in New Jersey, United States, among others worldwide. In hand specimens, pure Zn2SiO4 can be colorless to pale yellow, but trace impurities often impart greenish hues. The mineral is well known for its fluorescence, typically emitting bright blue to green under ultraviolet light.

Doped Zn2SiO4 is widely used as a phosphor host material. Activator ions such as Mn2+, Eu2+, and Tb3+ are incorporated to produce visible light emissions, with emissions tunable by the choice of dopant. Zn2SiO4-based phosphors have been utilized in older CRT displays and other fluorescent applications, and they continue to be studied for solid-state lighting and display technologies.

Synthesis methods for Zn2SiO4 include high-temperature solid-state reactions from ZnO and SiO2, as well as sol-gel, precipitation, and hydrothermal routes. Dopant incorporation is typically achieved during synthesis or via post-synthesis diffusion, enabling tailored optical properties for specific applications.