ECP and corresponding X-ray ICPs from Ca_1.8Eu_0.2Y_0.2Sn_0.8O₄ by beam-rocking near the [100] zone axis. (A) ECP. (B-F) ICPs of Ca-K_a, Sn-L, O-K_a, O-K_a, Eu-L, and Y-L emissions, respectively.

Figure shows the ECP and ICPs of Ca-K, Sn-L, O-K, Eu-L, and Y-L for the Ca_1.8Eu_0.2Y_0.2Sn_0.8O₄ sample near the [100] zone. The Eu-L ICP was closer to the Ca-K ICP, whereas the Y-L ICP was closer to Sn-L ICP. This suggests that the Eu and Y occupation sites could be biased, as expected. The coefficients, α_ix for i = Ca, Sn, and x = Eu, Y derived using Eq. (1), where n_Ca = 2/3 and n_Sn = 1/3. The k-factors of the constituent elements are calibrated in advance using a reference material with a known composition.. The site occupancies f_ix of the impurities, and the impurity concentrations c of all the samples are tabulated in Table 1.

In Ca_1.9Eu_0.2Sn_0.9O₄, Eu³⁺ occupied the Ca²⁺ and Sn⁴⁺ sites equally, consistent with the results of the XRD-Rietveld analysis. In contrast, Eu³⁺ and Y³⁺ occupied the Ca²⁺ and Sn⁴⁺ sites at ratios of approximately 7:3 and 4:6, respectively, in the co-doped samples, significantly biased as expected, but also maintaining the charge neutrality condition within the present experimental accuracies.

Table 1. Derived parameters (defined in text) of the samples of Ca_2-xEu_xSn_1-vY_vO₄ where (x, y) = (0.2, 0.0) and (0.2, 0.2).