Diffuse-reflectance and luminescence study of the reduction of samarium in lead borate

Trivalent samarium has been observed for the first time to be reduced to samarium(II) in lead borate matrices fired under an air atmosphere. Air-firing of equivalent masses of co-precipitated samarium(III):lead(II) borate and boric acid at 650 degrees C resulted in the reduction of a portion of the trivalent samarium to the divalent state. The diffuse reflectance spectrum characteristic of the sample as well as the low-temperature emission spectrum both provided confirmation of the reduction of samarium. The diffuse reflectance spectrum indicated a nearly complete reduction of the samarium ion, however, an immensely strong emission from residual trivalent samarium appeared to overwhelm the divalent samarium emission. Divalent samarium emission appears to be quenched at room temperature, but becomes apparent when cooled to 77K.