Nanocomposites and nanomaterials

Positron-positronium trapping model in application to polycrystalline BaGa2O4:Eu3+ ceramics
H. Klym1, Yu. Kostiv1, A. Luchechko1,2, I. Karbovnyk1,2

1Lviv Polytechnic National University, Bandery str., 12, Lviv-79013, Ukraine 
E-mail: halyna.i.klym@lpnu.ua, klymha@yahoo.com
2Ivan Franko National University of Lviv, 
Tarnavskogo str., 107, Lviv-79017, Ukraine

Polycrystalline BaGa2O4 ceramics are promising materials for different applications, in particular, as insulator materials in various optoelectronic devices, potential candidates for secondary electron emission coatings in plasma display panels etc. [1]. Investigation of BaGa2O4 ceramics are mainly focused on the study of their luminescent properties. In this work we studied changes in free volumes and nanopores of BaGa2O4:Eu3+ ceramics under the influence of incorporated Eu3+ ions into the base matrix using positron-positronium trapping model.
Samples of BaGa2O4 ceramics were obtained by solid-state reaction method from BaCO3 and Ga2O3 components with purity of 99.99%. Powders with 0, 1, 3 and 4 mol.% of Eu2O3 (99.99%) were mixed in an agate mortar for 6 h with further pressing in a steel mold. Prepared pellets were annealed at 1200 ºC for 12 h in air. After that, the annealing of ceramic samples was carried out at 1300 ºC for 4h [2]. 
It is established, that shown amount of free volumes correlates with addition phases near grain boundaries testified by XRD and EDX methods. Radii of nanopores calculated using Tao-Eldrup model are centered near 0.3 Å and 2 Å. Schematic models describing evolution of free volume in the studied ceramics were presented. 

1.	Noto L.L., Poelman D., Orante-Barrón V.R., Swart H.C., Mathevula L.E., Nyenge R., Chithambo M., Mothudi B.M., Dhlamini M.S. Photoluminescence and thermoluminescence properties of BaGa2O4 // Physica B: Condensed Matter. – 2018. – 535. – P. 268-271.
2.	Kostiv Y., Luchechko A., Klym H., Karbovnyk I., Sadovyi B., Zaremba O., Kravets O. Structural properties of polycrystalline BaGa2O4 ceramics doped with Eu3+ ions // XIth International Scientific and Practical Conference on Electronics and Information Technologies. – 2019. – P. 307-311.