The study aims to review the latest advancements in quaternary and quinary oxide systems. Most of the work concerning complex oxide systems involves compositions of glasses, glazes and, more recently, entropy stabilized ceramics. The latter refers to newly emerged materials developed by physicists and ceramists to investigate new or improved properties. The approach for the present study is based on a case study of complex fluorite oxide systems. Properties of reported compositions are presented by following the entropy mixing parameter. One interesting observation is that although the component oxides belong to different crystallographic systems, some of the compositions form unique solutions at high temperatures, which is claimed as an entropy stabilization effect by some authors. Composition-structure-property relationships in higher-order systems become very difficult to understand due to a lack of thermodynamic data, but the knowledge from doping and substitutional strategies used by ceramists in lower-order systems provide useful insights for experimental purposes. This research results show a perspective on a recent design method for ceramics which might give researchers and academics a tool in developing materials. This paper highlights fluorite-type structured oxides in quaternary and quinary systems.

Acknowledgments: This work is supported by the project “ANTREPRENORDOC”, in the framework of Human Resources Development Operational Programme 2014-2020, financed from the European Social Fund under the contract number 36355/23.05.2019 HRD OP /380/6/13 – SMIS Code: 123847.