Defects, diffusion and dopants in the ceramic mineral “Lime- Feldspar”

Calcium aluminosilicate, CaAl₂Si₂O₈, is a promising ceramic material that has found applications in several areas, such as glass production and petrology. Atomistic scale simulation techniques are used to study the intrinsic defects, Ca-ion migration paths and doping behavior in CaAl₂Si₂O₈. The most favorable defect is the Al–Si anti-site in agreement with the experimental observation. The O-Frenkel is the second most favorable defect. The Ca-Frenkel is higher in energy only by 0.62 eV than the O-Frenkel. Long-range Ca-ion migration is observed in the ac plane with the activation energy of 2.84 eV suggesting that Ca-ion diffusion in this material is slow. The prominent isovalent dopant on the Ca site is the Sr, which was experimentally substituted on the Ca site to prevent phase transformation. The formation of Ca interstitials and oxygen vacancies is favored by Fe³⁺ doping on the Si site. The favorable tetravalent dopant on the Si site and the Al site to form Ca vacancies is the Ge.