On the Luminescence of Some Tin-Activated Alkaline-Earth

The luminescence propert ies of some t in-act ivated alkal ine-earth or thophosphates, viz., ~-Caa(PO4)2, a-Sra(PO4)2, (~-Baa(PO~)2 and the magnes ium-modi f ied or thophosphates M2.~sMg0A~(PO4)2 (with M = Ca, Sr) and Ba2.ssMg0.~(PO4)z, were invest igated down to 4.2 K. The luminescence propert ies of these compos i t ions can be unders tood by assuming that there are two k inds of Sn ~ § centers in these lattices. The first type has a h igh coord inat ion umber and is respons ib le for an emiss ion band in the blue or UV part of the spectral region. The other type has a low coord inat ion umber and is responsi-b le for an emiss ion band in the yel low part of the spectral region. In some compos i t ions the yel low centers how AT and A~ emiss ion bands. The t in-act ivated alkal ine-earth o r thophosphates are known to be efficient phosphors (1-5). The st ructures of these compounds are rather complex with var ious sites for the d iva lent cations. For some of the magnes ium-modi f ied or thophosphates the s t ructure is not exact ly known. The luminescence propert ies of the var ious or thophosphates show a large variation. T in-act ivated ~-Sr~(PO~)2 and ~-Ba3