Absence of chromatic effect: crystal relaxation around Ce-III in Y1-xCexPS4 (0 <= x <= 1)

Ce-containing chalcogenides may exhibit interesting chromatic properties du e to the presence of a Ce-III-5f/Ce-III-4d gap. In such insulating material s, color varies from red to yellow depending on the covalent character of t he Ce-S bond. Thanks to this correlation, a continuous modification of the Ce-S bond characteristics may be induced to control the hue. Attempts in mo difying these bonds have been undertaken by synthesizing the solid solution Y1-xCexPS4 (x = 0, 0.005, 0.01, 0.05 and 0.1), YPS4 being colorless. The s ubstitution of Y3+ cations (rY(3+)(CN8) = 1.019 Angstrom) for Ce3+ cations (rCe(3+) (CN8) = 1.143 Angstrom) let expect a regular shift of the physical parameters deemed to influence the chromatic properties. Nevertheless, dif fuse reflectance measurements did not evidence any absorption threshold shi ft vs. x in the Y1-xCexPS4 series. The lack of sizeable influence of the Y/ Ce substitution on the color is correlated not only to the intrasite, band to band nature of the Ce-5f-->Ce-4d transition, but also to the occurrence of local relaxations around Ce in the YPS4:Ce solid solution insuring a che mical environment of the rare earth very similar to that observed in CePS4. EXAFS measurements performed at the Y-K and the Ce-L-III edges evidence th e maintaining of the average Y-S and Ce-S distances in the Y1-xCexPS4 solut ion from x=0 to x=1 as they are in the non-substituted end compounds YPS4 a nd CePS4. (C) 2000 Elsevier Science Ltd. All rights reserved.