Luminescence properties of piezoelectric single crystals with langasite structure

Luminescence properties of single crystals of langasite (LGS), langataite (LGT), and langanite (LGN) are investigated at 5 K by using synchrotron radiation as an exciting light source. Two emission bands are observed at 420 and 500 nm in LGS, at 410 and 460 nm in LGT, and at 500 and 535 nm in LGN. The origin of these bands is discussed by reference to the electronic structure of LGS.