Synthesis and structural characterization of Ca₁₂Ga₁₄O₃₃

Ca₁₂Ga₁₄O₃₃ was successfully synthesized using a wet chemistry technique to promote the homogenous mixing of the Ca and Ga cations. Rietveld refinements on X-ray and neutron powder diffraction data confirm that the compound is isostructural to Ca₁₂Al₁₄O_33, however, with a significantly larger lattice parameter allowing for the cages that result from the framework arrangement to expand. In naturally occurring Ca₁₂Al₁₄O₃₃, the mineral mayenite, these cages are occupied by O²⁻ anions, however, experimental studies exchanging the O²⁻ anions with other anions has led to a host of applications, depending on the caged anion. The functional nature of the structure, where framework distortions coupled with cage occupants, are correlated to electronic band structure and modifications to the framework could lead to interesting physical properties. The phase evolution was tracked using thermogravimetric analysis and high temperature X-ray diffraction and showed a lower formation temperature for the Ca₁₂Ga₁₄O₃₃ analogue compared to Ca₁₂Al₁₄O₃₃ synthesized using the same wet chemistry technique. Analyzing both X-ray and neutron powder diffraction using the Rietveld method with two different starting models results in one structural model, with one Ca position and the caged O on a 24d special position, being preferred.