Preparation and emission study of divalent samarium formed in air fired samples of Sm:Ba₂B₁₀O₁₇

Highlights: • Divalent samarium is formed in air fired samples of 5%Sm:Ba₂B₁₀O₁₇. • Minimal Sm(III) emission suggests significant reduction of the samarium ion when incorporated in 5%Sm:Ba₂B₁₀O₁₇. • The samarium(II) emission spectrum characteristic of 5%Sm:Ba₂B₁₀O₁₇ is reported for the first time. The samarium appears to be occupying a C_2v site. - Abstract: Trivalent samarium has been found to be reduced to the divalent state during the air firing process of the preparation of 5% Sm:Ba₂B₁₀O₁₅. This is the first time that the formation of divalent samarium has been reported as a function of the preparation of this material. The product was prepared from a co-precipitated borate which was fired at 750 °C with an additional 30% boric acid. The resulting product was confirmed by x-ray analysis and exhibited only divalent samarium emission. Based upon the observed emission, the primary samarium site can be assigned a site symmetry of C_2v. The emitting samarium ion appears to occupy a tetrahedral boron site in this material.