Investigation of hot pressing parameters of bismuth germanate (Bi4Ge3O12) scintillator ceramics

Reference	Presenter	Authors (Institution)	Abstract
12-023	Ivus Lorenzo Oliveira Matos	Matos, I.L.(Universidade Federal de Sergipe); Andrade, A.B.(Universidade Federal de Sergipe); Macedo, Z.S.(Universidade Federal de Sergipe); Giroldo Valério, M.E.(Universidade Federal de Sergipe);	The influence of pressure on uniaxial hot pressing has been investigated during the densification of bismuth germanate (BGO - Bi4Ge3O12). The powders were synthesized by solid-state reaction, mixed to a drop of PVA binder solution (0.1 g/ml) and conformed by uniaxial pressing under 15 MPa, at room temperature, as disks of 6 mm in diameter and 1.5 mm thick. They were then hot pressed in a thermomechanical analyzer (TMA - 60 Shimadzu), with pressure applied according to two different programs. In the first program, the pressure was continuously increased along the sintering temperature plateau and released before the cooling step. In the second program, the full pressure was applied at the beginning of the sintering plateau, and kept until the end of the cooling process. In both cases, the heating rate was 10 ºC/min, the binder was burned at 450 ºC for 30 min, the sintering temperature was 840 ºC and maximum pressure values of 0.10 MPa, 0.14 MPa or 0.18 MPa were tested. The structural analyses of synthesized powder and sintered ceramics were performed using X-ray powder diffraction using a Bruker D8 Advance equipped with a Cu tube. The measurements were obtained in continuous scan mode form 20° to 80° in 2? with a scan speed of 2°/min. The relative densities of sintered samples were measured according to Archimedes’ method. From the XRD results, it was observed that two different crystalline phases of bismuth germanate are present in the powder (namely, Bi4Ge3O12 and Bi12GeO20), while for the sintered sample, only the Bi4Ge3O12 phase was detected. Density measurements revealed a final relative density of 94 % for all the samples sintered according to the first hot pressing program, while relative densities higher than 95% were achieved for samples sintered following the second hot pressing program, under pressure of 0.18 MPa. The following steps of this work include microstructure and radioluminescence measurements of the scintillator ceramics produced.
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