Abstract
Three huntite-type aluminoborates of stoichiometry REAl3(BO3)4 (RE = Tb, Dy and Ho), namely, terbium/dysprosium/holmium trialuminium tetrakis(borate), were synthesized by slow cooling within a K2Mo3O10 flux with spontaneous crystallization. The crystal structures were determined using single-crystal X-ray diffraction (SC-XRD) data. The synthesized borates are isostructural to the huntite [CaMg3(CO3)4] structure and crystallized within the trigonal R32 space group. The structural parameters were compared to literature data of other huntite REAl3(BO3)4 crystals within the R32 space group. All three borates fit well into the trends calculated from the literature data. The unit-cell parameters and volumes increase linearly with larger RE cations whereas the densities decrease. All of the crystals studied were refined as inversion twins.
Highlights
K2Mo3O10 flux was used to synthesize REAl3(BO3)4 (RE = Tb, Dy, Ho) crystals, and the structural parameters of the synthesized Rare-earth aluminum borates (REAB) crystals were compared to literature data
The crystal structures of the synthesized REAB crystals are isostructural to the huntite structure (Mills, 1962) with the R32 space group (Fig. 1)
The huntite aluminoborates generally crystallize within the R32 space group; REAB compounds with RE = Pr, Nd, Sm, Eu, Tb, Ho, or Gd showed the transition in space group from R32 to lower symmetry monoclinic C2/c and C2 space groups in the disordered structures caused by variations in the growth temperature, cooling rate, and composition (Belokoneva & Timchenko, 1983; Belokoneva et al, 1988, 1994; Leonyuk & Leonyuk, 1995; Plachinda & Belokoneva, 2008; Leonyuk, 2017)
Summary
Rare-earth aluminum borates (REAB) with the general chemical formula REAl3(BO3) (RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) have been studied extensively for applications in lasers, nonlinear optics, sensors, and phosphors because of their optical and magnetoelectric properties as well as the capacity to be doped with other rare-earth metals (Koporulina et al, 2000; Leonyuk & Leonyuk, 1995; Leonyuk et al, 1998; Mills, 1962; Belokoneva & Timchenko, 1983; Belokoneva, 1994). The REAB crystals are promising materials for self-frequency-doubling lasers as their nonlinear optical properties can be changed by doping with different rare-earth elements including Nd, Dy, Er, Yb, Tm, or Y (Leonyuk et al, 1998, 2007; Foldvari et al, 2003; Chen et al, 2012).
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