Improvement of BGO ceramic scintillators through hot-pressing sintering methodology

Abstract

In the present work, the sintering of bismuth germanate through hot pressing and the improvement of scintillator performance were investigated. The linear shrinkage, crystalline structure, microstructure, transparency degree, and radioluminescence (RL) were studied as functions of the sintering pressure. X-ray diffraction revealed that the samples were predominantly composed of the Bi₄Ge₃O₁₂ phase, accompanied by small amounts of Bi₁₂GeO₂₀, with concentrations varying according to the sintering parameters. These concentrations were quantified through Rietveld refinement, which also indicated a tendency for the cell parameters to shrink as the sintering pressure increased. The microstructure of the ceramic pellets produced under varying hot-pressing parameters was investigated using scanning electron microscopy (SEM), revealing that while the grain size was preserved, the porosity and grain boundary thickness were reduced by the hot pressing, forming a quasicontinuum in some areas of the sample. The RL of all the samples exhibited a green color, with a maximum at 540 nm, ascribed to the transitions from the ³P_0,1,2¹P₁ excited states to the fundamental ¹S₀ state of the Bi³⁺ ions. For samples sintered under a pressure of .18 MPa, the enhancement in the optical transmittance, accompanied by a 61.36% increase in light output at the maximum wavelength, was observed.