Difference in Photoluminescence Properties of SnO₂:Eu³⁺Redish-Orange Phosphors Grown by Sol−Gel and Chemical Etching Methods

SnO2:Eu3+ reddish-orange phosphors were synthesized by chemically etching metallic Sn shots and Eu2O3 powder in aqueous HNO3 solution and subsequently calcined at Tc = 300−1200°C, and their photoluminescence (PL) properties were investigated in detail. All these phosphors, regardless of without or with calcination and its temperature values, show only the strong 5D0 → 7F1 magnetic-dipole transition lines. This is in direct contrast to those grown by the sol−gel method, where the low-temperature (≤1200°C) annealed PL spectra with direct excitation at λex = 464 nm dominate the 5D0 → 7F2 electric-dipole transition peaks.