AKTeO₂(CO₃) (A = Li, Na): The First Carbonatotellurites Featuring a Zero-Dimensional [Te₂C₂O₁₀]⁴– Cluster and a Wide Band Gap

) (NKTC) are 248 and 240 nm, respectively, and LKTC exhibits the largest experimental band gap (4.58 eV) among all of the tellurites containing the π-conjugated anionic groups reported. Theoretical calculations revealed that they exhibit moderate birefringences of 0.029 and 0.040@1064 nm, respectively.