The very first thorough investigation of the rare earth borosulfates RE2[B2(SO4)6] with RE = Y, La–Nd, Sm, Eu and Tb–Lu focusses on synthetic aspects and especially optical properties.

The first bismuth borosulfate (H 3 O)Bi[B(SO 4 ) 2 ] 4 is only the second featuring a three‐dimensional anion, the first tectosilicate‐analogous borosulfate synthesised solvothermally without a precursor (from Bi(NO 3 ) 3 ⋅5 H 2 O and B(OH) 3 in oleum); moreover, it is the first comprising two differently charged cations and crystallises in a new structure type in space group I (no. 82) (a=11.857(1), c=8.149(1) Å, 1947 refl., 111 param., wR2=0.037), confirmed by a second harmonic generation (SHG) measurement. The B(SO 4 ) 4 supertetrahedra are connected via all four sulfate tetrahedra resulting in a three‐dimensional anion with both H 3 O + and Bi 3+ cations in channels. Additionally, the crystal structure of a further bismuth borosulfate, Bi 2 [B 2 (SO 4 ) 6 ], is elucidated crystallising isotypically to the rare‐earth borosulfates R 2 [B 2 (SO 4 ) 6 ] in space group C2/c (No. 15) (a=13.568(2), b=11.490(2), c=11.106(2) Å, 3127 refl., 155 param., wR2=0.035). Moreover, the optical and thermal properties of both compounds are discussed.

An exploration of the crystal chemistry of exciting luminescent title compounds – possible phosphors – is discussed also employing magnetic measurements.

range from biothermal imaging, [5,6] temperature monitoring in catalysis, [7][8][9][10] microelectronics, [11] or molecular logics [12] to the investigation of fundamental thermodynamic phenomena [13] at the micro-and nanoscale. One of the conceptually simplest ways of optical temperature sensing, also in terms of the required setup, is the exploitation of the luminescence intensity ratio (LIR) of two emission bands due to radiative transitions from two thermally coupled excited levels of an ensemble of non-interacting ions. In case of efficient thermal coupling between these levels by (multi) phonon transitions, the LIR follows Boltzmann's law. [14] Trivalent lanthanoid ions with the rich energy level structure arising from their partially filled 4f n (n = 1-13) configuration are primary representatives for this type of luminescence thermometry, with Er 3+ and its green-emitting 2 H 11/2 and 4 S 3/2 levels being the most prominent examples. [7,15] Boltzmann-type equilibrium between the two excited levels critically depends on the interplay between the depopulating radiative decay and the nonradiative multiphonon thermalization pathways. [14,16] The rate-determining step is the Apart from the energy gap law, control parameters over nonradiative transitions are so far only scarcely regarded. In this work, the impact of both covalence of the lanthanoid-ligand bond and varying bond distance on the magnitude of the intrinsic nonradiative decay rate between the excited 6 P 5/2 and 6 P 7/2 spin-orbit levels of Gd 3+ is investigated in the chemically related compounds Y 2 [B 2 (SO 4 ) 6 ] and LaBO 3 . Analysis of the temperature-dependent luminescence spectra reveals that the intrinsic nonradiative transition rates between the excited 6 P J ( J = 5/2, 7/2) levels are of the order of only 10 ms −1 (Y 2 [B 2 (SO 4 ) 6 ]:Gd 3+ : 8.9 ms −1 ; LaBO 3 :Gd 3+ : 10.5 ms −1 ) and differ due to the different degree of covalence of the GdO bonds in the two compounds. Comparison to the established luminescent Boltzmann thermometer Er 3+ reveals, however, that the nonradiative transition rates between the excited levels of Gd 3+ are over three orders of magnitude slower despite a similar energy gap and the presence of a single resonant phonon mode. This hints to a fundamental magnetic dipolar character of the nonradiative coupling in Gd 3+ . These findings can pave a way to control nonradiative transition rates and how to tune the dynamic range of luminescent Boltzmann thermometers.

Borosulfates consist of heteropolyanionic networks of corner-shared (SO4)- and (BO4)-tetrahedra charge compensated by metal or non-metal cations. The anionic substructures differ significantly, depending on the different branching of the silicate-analogous...