Investigation of microstructure domains in rare-earth aluminum borates with huntite structure

Nominally pure and activated rare-earth aluminum borates of huntite-family, RAl3(BO3)4, are promising materials for lasers and nonlinear optics. Some of them typically show domain microstructure, which affects their functional properties sufficiently. In particular, twinning may degrade crystal quality and affect nonlinear optical properties, if crystals are composed of twin domains with opposing polarities. Here we propose to use X-ray natural circular dichroism (XNCD) effect to make an element selective map of the twinning of the laser-perspective crystals and demonstrate the existence of inversion twins unambiguously. Combining this experimental approach with the advantages of a new EBS-ESRF beam (radiation coherence, beam stability, and microfocusing), we will be able to fill a gap in the understanding of growth parameters-structure-properties relationships in conventional bulk crystals of rare-earth aluminum borates.