Growth, crystal structure and IR luminescence of KSrY1-xErx(BO3)2.

A series of novel KSrY1-xErx(BO3)2 (x = 0-1) phosphors that emit near-infrared radiation was synthesized using solid-state methods. Pure Y and Er crystals were grown using a KF flux via the top-seeded solution growth technique. In situ high-temperature single crystal X-ray diffraction, Raman spectroscopy and DFT calculations were used for characterization. Within the series, a polymorphic phase transition from space group P21/m to R3m was discovered between 550 and 600°C. The concentration dependence of the luminescence intensity was measured for the samples. A strong emission of Er3+ electron transition 4I13/2 → 4I15/2 was detected within the 1529-1549 nm range, with the maximum observed for the KSrY0.4Er0.6(BO3)2 composition.

Systematic rare Earth doping to adopt an R32 type huntite structure in NdSc3(BO3)4 crystals.

This study is focused on determining the type and quantity of REE impurities responsible for converting the structure of NdSc3(BO3)4 into an R32 polymorph. According to the single crystal X-ray diffraction of RxNdyScz(BO3)4 (R = Sm-Lu, x + y + z = 4) the samples probably contain several polymorphic modifications. However, the predominant structure has been defined as R32 for R = Eu, Er, Tm, and Yb and P3221 for R = Sm, Gd, Tb, Dy, and Ho. Another potential limitation to the future use of the crystals is a compositional zoning found in the crystals with significant substitution in the scandium position.

Synthesis and Growth of Rare Earth Borates NaSrR(BO3)2 (R = Ho-Lu, Y, Sc).

NaSrR(BO3)2 (R = Ho-Lu, Y, Sc) compounds were obtained for the first time. Their structures exhibit disordered positions of Sr2+ and Na+ atoms while RO6 polyhedra are connected through the BO3 groups. Large distances between R atoms and high transparency in the range of 250-900 nm make them promising for phosphor applications. A pathway to obtain single crystals was shown by growing NaSrY(BO3)2 and NaSrYb(BO3)2 by the top seeded solution growth method with Na2O-B2O3-NaF flux.

Study of an EuBO3-ScBO3 system and EuSc3(BO3)4, EuSc(BO3)2 orthoborates.

The EuBO3-ScBO3 system was investigated by solid state synthesis and DSC methods. In this system, a new EuSc(BO3)2 compound was found. It crystallizes in the R3̄ space group with unit cell parameters of a = 4.8939(1) Å and c = 16.2663(5) Å. Whereas another compound in the system EuSc3(BO3)4 possesses two modifications: a low-temperature α-C2/c (a = 7.687(1) Å, b = 9.810(2) Å, c = 12.021(2) Å, and ß = 105.379(4)°) and a high-temperature ß-R32 (a = 9.7473(1) Å and c = 7.9205(2) Å). The α-EuSc3(BO3)4 crystal was grown with LiBO2-LiF flux, and ß-EuSc3(BO3)4 was obtained by the solid state synthesis. All of the obtained crystals exhibited typical Eu3+ luminescence spectra with peaks at 589 nm, 596 nm, 615 nm, 657 nm and 689 nm, which corresponded to the 5D0 → 7FJ (J = 0, 1, 2 and 4) electron transitions. The strongest peak of luminescence was located at 615 nm and corresponded to the 5D0 → 7F0 transition.