The Ba3Y2–xErx(BO3)4 (х = 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) phosphors were obtained by crystallization from a
melt. The Ba3Y2(BO3)4 crystal structure was refined from single crystal X-ray diffraction data to R = 0.037. Its
anisotropic atomic displacement parameters for all atoms were refined for the first time. The borate crystallizes
in the orthorhombic crystal system, space group Pnma with unit cell parameters a = 7.673(1), b = 16.44(1), c =
8.977(2) Å, V = 1132.3(3) Å3, Z = 4. These phosphors are isotypical to those of the A3M2(BO3)4 (A = Ca, Sr, Ba,
M = Ln, Y, Bi) family. The crystal structure contains the isolated BO3 triangles, two general and a special one
independent crystallographic sites for large cations, which are disordered over sites. Thermal behavior of
Ba3Y2(BO3)4 was investigated by high-temperature X-ray powder diffraction and thermal expansion coefficients
are calculated in a wide temperature range. An inflections of temperature dependencies of the unit cell parameters
is observed in a range 600–740 ◦C. Luminescence spectra, excitation and kinetic curves of the
Ba3Y2(BO3)4:Er3+ series are reported. A maximum luminescence intensity is observed for the x = 0.1 sample.
According to vibrational spectroscopy data no structural changes upon activation of the Ba3Y2(BO3)4 matrix with
the Er ions are observed.