2019, Vol.29, No.1

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

The physical properties of ceramic materials including oxides are greatly influenced by the material density. Therefore, various efforts have been made to increase the material density. One of the most popular strategies is to use sintering additives in sintering materials. The conventional sintering additive was a spherical powder having a threedimensional structure. In this study, sintering additive with 2-dimensional (2D) layer structure was used to increase the sintering density of cerium oxide and its effect was confirmed. In this study, 1 nm-thick TiOx and MnOx nanosheets were used as sintering additives.

Methylammonium lead halide (MAPbX3, X = I, Br) thin films, used as the light absorber of perovskite solar cells, were prepared using the dual feed ultrasonic spray method. Going through a deposition at a substrate temperature of below 60 o C and then a final heat treatment at 75 o C for 5 minutes using dual feed ultrasonic spray method, MAPbI3 single phase could be formed. Whereas undergoing a deposition at temperatures above 80 o C, the spheroidal grains could be changed into rod-shaped fractal structures due to the decomposition of the perovskite phase. Furthermore, using the same method at a higher heat treatment temperature of 100 o C, MAPbI3−xBrx thin films could also be formed from MAPbI3 and MAPbIBr2 solution.

The spherical SiO2 powders were synthesized by the scaled-up ultrasonic pyrolysis (USP). The aqueous SiO2 sol, which contained 20~30 nm SiO2 particles, was used as a precursor for the scaled-up USP. The effects of the USP operating conditions and precursor conditions were systematically investigated, including reaction temperature, gas flow rate, and the concentration of SiO2 sol on the morphologies of synthesized SiO2 particles. the synthesized SiO2 particle showed a pseudo-crystal phase, spherical morphology, and a smooth surface. The size of the spherical SiO2 particle decreased as both reaction temperature increased and precursor concentration decreased. In addition, the synthesized SiO2 particle size was increased by increasing the gas flow rate. Lastly, the scaled-up USP was compared with the lab-scale USP based on the same process conditions. Due to a short retention time in the reaction tube during the USP process, the SiO2 particle synthesized via the lab-scale USP showed a larger particle size.