Crystallization from glass can be a powerful process to elaborate innovating transparent materials for optical and photonic applications if nucleation and crystal growth steps can be precisely controlled. This talk will focus on two main applications: transparent polycrystalline ceramics elaborated by full and congruent crystallization from glass and nanostructured glass-ceramics designed from nanoscale phase separated glasses.
Transparent polycrystalline ceramics elaborated by full crystallization from glass
Transparent ceramics are an emerging class of optical materials competing with single crystal technology for a broad range of applications. Ceramics offer several advantages, particularly in the fabrication of complex shapes and large-scale industrial production, and enable great and homogenous doping of optically active ions. However, up to date, only a limited number of cubic or nanocrystalline transparent polycrystalline ceramics requiring complex and expensive synthetic approaches has been reported. Our recent work shows the possibility to obtain new transparent ceramics by full and congruent crystallization from glass. This is demonstrated in the case of several new compositions, such as BaAl4O7, Sr3Al2O6 and Sr3Ga2O6, all showing high transparency in the visible and infra-red ranges. Lately, we have focused our work on large scale and highly transparent strontium aluminosilicate compositions. A crystallographic study coupled to NMR experiments and DFT calculations of the birefringence evidences the role of structural disorder (Al/Si substitution and presence of vacancies on strontium sites) to explain the optical isotropy observed in these hexagonal materials. These results propose an innovative concept, the addition of a controlled structural disorder within crystalline structures, in order to lower the birefringence and to elaborate new transparent ceramics.
Transparent nanostructured glass and glass-ceramics