title: Structural phase transitions and photoluminescence properties of oxonitridosilicate phosphors under high hydrostatic pressure.
abstract: Spectroscopic properties of a series of (Sr0.98-xBaxEu0.02)Si2O2N2(0 ≤ x ≤ 0.98) compounds has been studied under high hydrostatic pressure applied in a diamond anvil cell up to 200 kbar. At ambient pressure the crystal structures of (Sr0.98-xBaxEu0.02)Si2O2N2(0 ≤ x ≤ 0.98) are related to the ratio of strontium to barium and three different phases exists: orthorhombic Pbcn(0.78 ≤ x ≤ 0.98), triclinic P1 (0 < x ≤ 0.65) and triclinic P1 (0.65 < x < 0.78). It was found that Eu2+luminescence reveals abrupt changes under pressure (decay time, energy and shape) which indicate the variation of the local symmetry and crystal field strength in Eu2+sites. These changes are attributed to the reversible pressure-induced structural phase transitions of triclinic (Sr0.98-xBaxEu0.02)Si2O2N2into orthorhombic structure. Pressure in which phase transition occurs decreases linearly with increasing of Ba composition in (Sr0.98-xBaxEu0.02)Si2O2N2series. Additionally, very different pressure shifts of the Eu2+luminescence in different phases of (Sr0.98-xBaxEu0.02)Si2O2N2:Eu from -40 cm-1/kbar to 0 cm-1/kbar have been observed. This effect is explained by different interaction of the Eu2+5d electron with the second coordination sphere around the impurity cations.
authors.affiliation: Institute of Experimental Physics, Faculty of Mathematics, Physics and Informatics, University of Gdansk, WitaStwosza 57, 80-308 Gdansk, Poland.
authors.forename: Agata
authors.initials: A
authors.lastname: Lazarowska
authors.affiliation: Institute of Experimental Physics, Faculty of Mathematics, Physics and Informatics, University of Gdansk, WitaStwosza 57, 80-308 Gdansk, Poland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Mahlik
authors.affiliation: Institute of Experimental Physics, Faculty of Mathematics, Physics and Informatics, University of Gdansk, WitaStwosza 57, 80-308 Gdansk, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Grinberg
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.|Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China.
authors.forename: Guogang
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.|Department of Mechanical Engineering and Graduate Institute of Manufacturing Technology, National Taipei University of Technology, Taipei 106, Taiwan.
authors.forename: Ru-Shi
authors.initials: RS
authors.lastname: Liu