Effects of A-site cations and the substitution site on the upconversion luminescence of Er3+ in the zirconate perovskite series

We investigated the upconversion luminescence (UCL) properties of AZrO(3) (A = Ca, Sr, and Ba) perovskite compounds co-doped with Er3+ and Yb3+ in relation to the change in the crystal structure from orthorhombic to cubic. The dopants selectively substituted the A- and B-site ions in the ABO(3) -type perovskite structure. Upon excitation at 980 nm, we observed the two main UCL features at 545 nm and 660 nm, which depended strongly on the ion occupying the A-site and whether the dopant substituted the ion occupying the A- or the B-site. The intensity of the UCL was found to be maximized for A = Ca because this ion resulted in the lowest crystal symmetry of the host material. The dependence of the UCL on the substitution site (A or B) was significant for A = Sr, in accordance with the sizable difference in the lattice constants of host materials doped at either the A-site or B-site. Our results showed that the crystal symmetry of the host materials and the related local lattice symmetry could play an important role in determining the emission properties of Er3+ ions in perovskite crystals.