Phase Equilibria and Tin-Activated Luminescence in Strontium Orthophosphate Systems

Abstract

Strontium orthophosphate undergoes a rapid, reversible transition at 1305°C. The high‐temperature β form of pure Sr3false(PO4)2 cannot be quenched to room temperature, even with extremely rapid cooling. Determination of phase relationships on the orthophosphate joins between Sr3false(PO4)2 and each of the three orthophosphates, Mg3false(PO4)2 , Ca3false(PO4)2 , and Zn3false(PO4)2 showed that they form β‐ Sr3false(PO4)2 solid solutions which could be cooled to room temperature to form the basis for the so‐called “modified strontium orthophosphate” phosphors. The ranges of composition and temperature over which the β‐ Sr3false(PO4)2 solid solutions exist were determined for each system, and the existence of two ternary compounds, SrMg2false(PO4)2 and SrZn2false(PO4)2 , was confirmed. The latter compound has a transition at 1035°C, but the high‐temperature form can be maintained at room temperature only by extremetly rapid quenching. Equilibrium diagrams of each of the systems are presented to show all stability relationships.The behavior of tin‐activated β‐ Sr3false(PO4)2 solid solution phosphors in each of the three systems was explored under 2537Aå excitation, and the relation of phosphor composition to quantum efficiency, brightness, and temperature stability in the lamp‐making range was determined. The tin‐activated luminescence of the two ternary compositions was investigated using 2537Aå, 3650Aå, and cathode ray excitation.

Synthesis and X-ray Powder Diffraction Study of New Phosphates in the Cu3(PO4)2–Sr3(PO4)2 System: Sr1.9Cu4.1(PO4)4, Sr3Cu3(PO4)4, Sr2Cu(PO4)2, and Sr9.1Cu1.4(PO4)7

“…Phase diagrams M (PO ) }Sr (PO ) were investigated for M"Ca, Mg, Zn (1) and Cd (2). The existence of solid solutions, Sr \V Mg V (PO ) (0.274x41.08 at 10003C), Sr \V Zn V (PO ) (0.274x40.81 at 10253C), and Sr \V Cd V (PO ) (0.364x40.63 at 10003C), isotypic with -Sr (PO ) and compounds, SrMg (PO ) , -SrZn (PO ) , and SrCd (PO ) , with unknown crystal lattices was found (1,2).…”

“…The displacement of strontium cations in the M3 site from site 9e in the center of symmetry ( , , 0) to the half-occupied 18h site (x, !x, z) gave B"1.4 (1). The crystal structure re"nement of Sr Co (PO ) (36) from single-crystal data showed that in reality strontium cations in the M3 sites are disordered over four positions.…”

Hydrothermal synthesis and luminescent properties of Sb3+-doped Sr3(PO4)2

“…Butler [10] described some alkaline earth orthophosphate phosphors consists of calcium, strontium and barium. Sarver and coworkers [11] reported the luminescence of tin activated strontium orthophosphate. Koelmans and Cox [12] also investigated the luminescence of modified tin activated strontium orthophosphate and found that modified tin activated Sr 3 ðPO 4 Þ 2 could give a strong red luminescence with a maximum peak at about 630 nm under excitation with 253.7 nm.…”

Synthesis and Characterization of New Strontium Iron(II) Phosphates, SrFe2(PO4)2 and Sr9Fe1.5(PO4)7

“…The M (PO ) }Sr (PO ) systems were investigated for M"Ca, Mg, Zn (1), and Cd (2). Sarver et al (1) (13), and Sr Cu(PO ) (13). The compound Sr Cu (PO ) crystallizing in orthorhombic system has also been described (13).…”