The ferroelectricity of multivalent codoped Bismuth ferrite (BiFeO₃; BFO) nanoparticles (NPs) is revealed and utilized for photocatalysis, exploiting their narrow electronic bandgap. The photocatalytic activity of ferroelectric photocatalysts BiFe_0.95Mn_0.05O₃ (BFM) NPs and mono‐, di‐, or tri‐valent cations (Ag⁺, Ca²⁺, Dy³⁺; MDT) coincorporated BFM NPs are studied under ultrasonication and in acidic conditions. It is found that such doping enhances the photocatalytic activity of the ferroelectric NPs approximately three times. The correlation of the photocatalytic activity with structural, optical, and electrical properties of the doped NPs is established. The increase of spontaneous polarization by the mono‐ and tri‐valent doping is one of the major factors in enhancing the photocatalytic performance along with other factors such as stronger light absorption in the visible range, low recombination rate of charge carriers, and larger surface area of NPs. A‐site doping of BFO NPs by divalent elements suppresses the polarization, whereas trivalent (Dy³⁺) and monovalent (Ag+) cations provide an increase of polarization. The depolarization field in these single domain NPs acts as a driving force to mitigate recombination of the photoinduced charge carriers.

Laser fragmentation of colloidal submicron-sized bismuth ferrite particles was performed by irradiating a liquid jet to synthesize bismuth ferrite nanoparticles. This treatment achieved a size reduction from 450 nm to below 10 nm. A circular and an elliptical fluid jet were compared to control the energy distribution within the fluid jet and thereby the product size distribution and educt decomposition. The resulting colloids were analysed via UV-VIS, XRD and TEM. All methods were used to gain information on size distribution, material morphology and composition. It was found that using an elliptical liquid jet during the laser fragmentation leads to a slightly smaller and narrower size distribution of the resulting product compared to the circular jet.

The escalated photocatalytic (PC) efficiency of the visible light absorber Ba-doped BiFe_0.95Mn_0.05O₃ (BFM) nanoparticles (NPs) as compared to BiFeO₃ (BFO) NPs is reported for the degradation of the organic pollutants rhodamine B and methyl orange.

Bi-based halide perovskites have been considered as an alternative to Pb-based perovskites with the intent not to use lead in the field of photovoltaics. Over the last few years, the novel Bi-based halide perovskites have shown potential to reach good photovoltaic performance suggested by their similar electronic structure to Pb-based perovskites. Nevertheless, their lower dimensionality entails poor charge carrier transport. It has been consistently raised that the role of the A-site has to be further studied. To explore this proposition, we have synthesized three different Bi-based halides with a substitution on the A-site by Azetidinium cations. In this contribution we report fundamental observations of the Azetidinium bismuth halides, [(CH₂)₃NH₂]₃Bi₂I₉, [(CH₂)₃NH₂]₃Bi₂Br₉, and [(CH₂)₃NH₂]₃Bi₂Cl₉ with perspectives in optoelectronics and photovoltaics. These new materials present 0D and 2D crystal structures at a molecular level and an optical feature of an excitonic band state.

It is still an open question if magnetoelectric coupling occurs at the atomic scale in multiferroic BiFeO 3 . Nuclear solid-state techniques monitor local fields at the atomic scale. Using such an approach, we show that, contrary to our own expectation, ferroelectric and magnetic ordering in bismuth ferrite ( BiFeO 3 or BFO) decouple at the unit-cell level. Time differential perturbed angular correlation (TDPAC) data at temperatures below, close, and above the magnetic Néel temperature show that the coupling of the ferroelectric order to magnetization is completely absent at the bismuth site. It is common understanding that the antiferromagnetic order and the cycloidal ordering due to the Dzyaloshinskii-Moriya interaction generate a net zero magnetization of the sample canceling out any magnetoelectric effect at the macroscopic level. Our previous data show that a very large coupling of magnetic moment and electrical distortions arises on the magnetic sublattice (Fe site). The oxygen octahedra around the iron site experience a large tilt due to the onset of magnetic ordering. Nevertheless, the Bi-containing complementary sublattice carrying the largest part of ferroelectric order is practically unaffected by this large structural change in its direct vicinity. The magnetoelectric coupling thus vanishes already at the unit cell level. These experimental results agree well with an density functional theory (DFT) calculation. Published by the American Physical Society 2025

In the last decade, organic–inorganic hybrid halide perovskite materials have developed into a very large research area in photovoltaics and optoelectronics as promising light harvesters. Lead-free double perovskites have recently been investigated as an environmentally friendly alternative to the lead-containing compositions. However, lead-free organic–inorganic hybrid halide double perovskites have so far rarely been produced due to a certain complexity in their synthesis. A number of small molecular cations have been investigated, but compositions containing azetidinium, which is a 4-membered heterocyclic molecular ring, on the A-site have hardly been considered. This study investigates the potential of [(CH₂)₃NH₂]₂AgBiBr₆ as an optical absorber in photovoltaics or optoelectronics. The use of this alternative cation changes the crystal symmetry significantly. Columns of alternating metal cation form which are separated by the organic ions. While crystal symmetry is rather different from the perovskites, the overall properties as an absorber are similar. It is thus worthwhile to further investigate alternate hybrid compositions which form into other symmetries than the perovskite base structure.