Evolution of core–rim structures and phase transformations in infra-red transmitting Y-α-SiAlON ceramics

• Published in: Journal of the European Ceramic Society Vol. 42; no. 4; pp. 1354 - 1361
• Main Authors: Sheng, Yu, Gu, Hui, Xing, Juan-Juan, Li, Jiang-Tao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2022
• Subjects: Core–rim structures; Infrared transmittance; Liquid phase sintering; Phase transformation; α-SiAlON ceramics; Core–rim structures; Phase transformation; Infrared transmittance; Liquid phase sintering; α-SiAlON ceramics
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2021.11.057

Core–rim structures were observed as common features in Y-α-SiAlON ceramics hot-pressed between 1550−1950 °C. We found most dopants were taken into α’-rims, and a transition layer grown first on α-cores from liquid-phase over-saturated with metal solutes. Elongated β’-grain were formed as minor phase with α’- or AlN-cores thus only after the α’ matrix had consumed up all Y solutes, revealing that the α’ → β’ transformation is controlled by the transient liquid-phase and similar defects and dangling bonds could be detected in both SiAlON phases by cathodoluminescence. Quantitative assessment of Ym/3Si12−(m+n)Alm+nOnN16−n demonstrates the multiphase evolution, initiated by over-saturation of Y solutes at low temperatures thus retaining α-phase as cores to lower the infra-red transmittance, dictated by homogenization of Al solutes at higher temperature. The elimination of those phase boundaries leads to better dopant and sintering design for achieving transparent and high-performance SiAlON ceramics.