Doping of Lanthanum(III) Orthoborates and Metaborates with Europium(III) and Yttrium(III) Ions

Abstract

Orthoborates La_{0.95 – х}Eu_0.05Y_хBO₃ and metaborates La_{0.95 – х}Eu_0.05Y_х(BO₂)₃ (х = 0.025; 0.05; 0.075; 0.1; 0.2; 0.4; 0.6; 0.8; 0.95) are synthesized under optimal conditions by the extraction pyrolytic method at a lower temperature and a shorter time as compared to the known methods. In single-phase systems, the unit cell volume in La_{0.95 – х}Eu_0.05Y_хBO₃ (aragonite structural type) and La_{0.95 – х}Eu_0.05Y_х(BO₂)₃ (α-type monoclinic polymorph) decreases with an increase in the Y³⁺ ion content. Under excitation at an Eu³⁺ ion luminescence maximum λ_em = 615 nm, the compounds have similar luminescence excitation spectra in the region of 230–320 nm. An increase in the Y³⁺ ion content (x ≥ 0.1) in both orthoborates La_{0.95 – х}Eu_0.05Y_хBO₃ and metaborates La_{0.95 – х}Eu_0.05Y_х(BO₂)₃ leads to a certain change in the location and intensity distribution of transition bands because the nearest environment of the Eu³⁺ ion in these compounds is transformed upon transition from one structural type to another. The introduction of the Y³⁺ ion into La_0.95Eu_0.05BO₃ (5 mol %) or La_{0.95 – х}Eu_0.05(BO₂)₃ (10 mol %) leads to an increase in the integral luminescence intensity. A further increase in the Y³⁺ ion content decreases the luminescence intensity.