Crystal structure, photoluminescence and cathodoluminescence of Ba_1-xSr_xAl₂O₄ doped with Eu²⁺

Abstract

Herein we describe the synthesis, crystal structures, photoluminescence (PL) and cathodoluminescence (CL) spectra of phosphors in the Sr 0.97-x Ba x Eu 0.03 Al 2 O 4 system between x = 0 and x = 0.97. The syntheses of these phosphors were carried out by solid state reactions at 1350°C in mixed gas (H 2 /N 2 ). The molar fractions of the alkaline earth elements were varied in steps of 0.1. The Sr 1-x Ba x Al 2 O 4 series manifested solid solutions of a monoclinic phase (at the Sr-rich side) and a hexagonal phase (at the Ba-rich side). At the Ba-rich side of Sr x-1 Ba x Al 2 O 4 :Eu 2+ we found evidence in the PL spectra that the hexagonal phase differed as the x Ba fraction changed: it changed at room temperature from the ferroelectric P6 3 structure at x Ba =1 to the paraelectric P6 3 22 phase at x Ba ≈0.9 and at x Ba ≈0.8 it went back to P6 3 . Unlike the PL spectra, the CL spectra of the hexagonal phase of Sr 0.97-x Ba x Eu 0.03 Al 2 O 4 at x ≥ 0.5 indicated only the paraelectric P6 3 22 phase at room temperature.