Morphology and crystal phase evolution of GeO2 in liquid phase deposition process

► Rod-like tetragonal GeO2 phases precipitate out of solution ahead of truncated cube-like hexagonal GeO2 phases. ► Fast growth of tetragonal GeO2 along [111] direction leads to development of a rod-like shape. ► Tetragonal phases undergo re-dissolution as the hexagonal phases come forth. ► Re-dissolving behavior conflicts with classic crystal growth kinetics but is furthered by high thermodynamical stability of the hexagonal phase and by a fluctuant way in release of GeO2 solutes by germanate ions. ► LPD synthesis of GeO2 products can be expanded from hexagonal particles or film to the one-dimensional tetragonal structure.