Materials Development Division

Crystal Chemistry

Satoshi UDA

Prof.Satoshi UDA

  • Assoc. Prof. Junpei OKADA
  • Assist. Prof. Jun NOZAWA
  • Assist. Prof. Hiromasa NIINOMI

Lead New Growth Methods with Optimizing Interfacial Energies by Applying External Fields

Development of almost every functional material and device in the area of information technology has been aided by the research of the associated single crystal. This lab is concerned with the novel approach mainly for the growth from the melt by studying the relationship between the interface dynamics during growth and properties of grown crystals.

Special interests lie in the growth of new crystals via the manipulation of the interface dynamics (1) by the imposition of an interface-electric, -magnetic and -stress fields and (2) by the change of the solid-liquid energy relationship through the thermal or mechanical treatment on the solid or liquid. Combining these approaches will also shed new light on the crystal growth that has never been successful. Crystals developed this way will widen an application opportunity in the piezoelectric, magnetic, optic and other fields related to the highly-networked information society.

crystal growth, chemical potential, applying external fields, solute partitioning
Model of crystallization

During growth of Ca3Ta(Ga1-xAlx)3Si2O14 crystal, a langasite-type crystal with A3BC3D2O14 structure, Al and Ga in the melt are partitioned into crystal with the equilibrium partition coefficient of unity regardless of the Al/Ga ratio. An Al-Ga complex, ‘C’, that is thermodynamically equivalent to C-site in a crystal is present in the melt, which is partitioned into crystal to become C site (Fig. 1(a)). Fig 1(b) demonstrates the equal chemical potentials in C-site and ‘C’ complex at Al=Ga=0.5.

The equilibrium partition coefficient of Mg, kE0, varied with the amount of MgO in the LiNbO3 melt and a discontinuity in the kE0 variation was found around 3.8 mol%. This is attributed to the change of Mg occupation site from Li site to Li site + Nb site in LiNbO3 where the crystal structure changes discontinuously.

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