Stress‐induced crystal axis spiral rotation in multiferroic β'‐Gd₂(MoO₄)₃ observed only in glass crystallization

Abstract

Stress-induced crystal axis spiral rotation in multiferroic β'-Gd 2 (MoO 4) 3 crystals observed only in the crystallization of Gd 2 O 3-MoO 3-B 2 O 3 glasses is a new world of glass-crystallization being beyond the usual crystal growth engineering. The selfpowdering phenomenon in crystals synthesized in an electric furnace and the appearance of periodic birefringence images observed in laser-patterned single crystal lines are reviewed together with some new data. Extremely large stresses are created at the interface between super-cooled liquids and crystals due to the density difference between glasses/liquids with larger density and crystals with smaller density, and the crystal axis spiral rotation is induced in β'-Gd 2 (MoO 4) 3 crystals in order to relax and release stresses at the interface. The structural origin of the density difference between glasses and crystals is discussed, and the uniqueness of the crystallization of Gd 2 O 3-MoO 3-B 2 O 3 glasses is emphasized. The possibility of the synthesis of dense bulk glass-ceramics with β'-Gd 2 (MoO 4) 3 crystals is tried using a slow melt-cooling processing. K E Y W O R D S birefringence imaging, crystal axis spiral rotation, glass crystallization, laser patterning, multiferroic β'-Gd 2 (MoO 4) 3 , self-powdering phenomenon, stress F I G U R E 1 DTA pattern at room temperature for the meltquenched sample with the composition of 21.25Gd 2 O 3-63.75MoO 3-15B 2 O 3 glass (21.25GdMoBO glass). Heating rate was 10 K/min 27 F I G U R E 2 Temperature dependence of magnetic susceptibility (χ M) and inverse susceptibility (χ M −1) for 21.25GdMoBO glass under zero-field cooled (ZFC) and field-cooled (FC) conditions 45 [Color figure can be viewed at wileyonlinelibrary.com] How to cite this article: Komatsu T, Honma T. Stress-induced crystal axis spiral rotation in multiferroic β'-Gd 2 (MoO 4) 3 observed only in glass crystallization.

A new perspective for nucleation and nanocrystallization from interfacial energy and nanoscale composition fluctuations in glasses

“…Nowadays, the existence of spatially and compositionally heterogeneous structures in multicomponent oxide glasses has been well established through experiments and simulations. [17][18][19][20][21][22][23][24][25][26][27] The present authors' group [28][29][30][31][32] extended the fragility concept proposed by Angell 33,34 28,30 The presence of Li 2 O/Nb 2 O 5 -rich fragile regions would have advantages for the nucleation and growth of LiNbO 3 from the viewpoints of viscosity, diffusion, and chemical composition. Nanoscale composition fluctuations for LNS glasses based on the DNCF model are schematically shown in Figure 3.…”

“…Nowadays, the existence of spatially and compositionally heterogeneous structures in multicomponent oxide glasses has been well established through experiments and simulations 17–27 . The present authors’ group 28–32 extended the fragility concept proposed by Angell 33,34 to local composition fluctuations in multicomponent oxide glasses, that is, the DNCF model. That is, multicomponent oxide glasses consist of nanoscale network former‐rich strong region and nanoscale network modifier‐rich fragile region and nucleation is initiated preferentially in the nanoscale fragile region.…”

“…On the other hand, the MRO structure in glasses is related to the linkage style of SRO structural units and is characterized by “density fluctuations” and “composition fluctuations” at nanoscale levels, that is, “nanoscale heterogeneous structures.” 17–27 Nowadays, it is very important to clarify concretely the nanoscale heterogeneous structure, for example, their chemical composition, fraction, and connectivity, in a given glass. Recently, the present authors’ group 28–32 tried to explain the nucleation process and crystallization sequence (the formation order of crystalline phases) in various multicomponent oxide glasses by using the model of the distribution of nanoscale composition fluctuations (DNCF) and the concept of Ostwald's step rule (rule of stages).…”

“…[17][18][19][20][21][22][23][24][25][26][27] Nowadays, it is very important to clarify concretely the nanoscale heterogeneous structure, for example, their chemical composition, fraction, and connectivity, in a given glass. Recently, the present authors' group [28][29][30][31][32] tried to explain the nucleation process and crystallization sequence (the formation order of crystalline phases) in various multicomponent oxide glasses by using the model of the distribution of nanoscale composition fluctuations (DNCF) and the concept of Ostwald's step rule (rule of stages).…”