Intralanthanide Separation on Layered Titanium(IV) Organophosphate Materials via a Selective Transmetalation Process

The lanthanides (Ln) are an essential part of many advanced technologies. Our societal transformation toward renewable energy drives their ever-growing demand. The similar chemical properties of the Ln pose fundamental difficulties in separating them from each other, yet high purity elements are crucial for specific applications. Here, we propose an intralanthanide separation method utilizing a group of titanium­(IV) butyl phosphate coordination polymers as solid-phase extractants. These materials are characterized, and they contain layered structures directed by the hydrophobic interaction of the alkyl chains. The selective Ln uptake results from the transmetalation reaction (framework metal cation exchange), where the titanium­(IV) serves as sacrificial coordination centers. The “tetrad effect” is observed from a dilute Ln³⁺ mixture. However, smaller Ln³⁺ ions are preferentially extracted in competitive binary separation models between adjacent Ln pairs. The intralanthanide ion-exchange selectivity arises synergistically from the coordination and steric strain preferences, both of which follow the reversed Ln contraction order. A one-step aqueous separation of neodymium (Nd) and dysprosium (Dy) is quantitatively achievable by simply controlling the solution pH in a batch mode, translating into a separation factor of greater than 2000 and 99.1% molar purity of Dy in the solid phase. Coordination polymers provide a versatile platform for further exploring selective Ln separation processes via the transmetalation process

Cycloheptatrienyl-Cyclopentadienyl Heteroleptic Precursors for Atomic Layer Deposition of Group 4 Oxide Thin Films

Atomic layer deposition (ALD) processes for the growth of ZrO₂ and TiO₂ were developed using novel precursors. The novel processes were based on cycloheptatrienyl (CHT, -C₇H₇) – cyclopentadienyl (Cp, -C₅H₅) compounds of Zr and Ti, offering improved thermal stability and purity of the deposited oxide films. The Cp^MeZrCHT/O₃ ALD process yielded high growth rate (0.7–0.8 Å/cycle) over a wide growth temperature range (300–450 °C) and diminutive impurity levels in the deposited polycrystalline films. Growth temperatures exceeding 400 °C caused partial decomposition of the precursor. Low capacitance equivalent thickness (0.8 nm) with low leakage current density was achieved. In the case of Ti, the novel precursor, namely CpTiCHT, together with ozone as the oxygen source yielded films with low impurity levels and a strong tendency to form the desired rutile phase upon annealing at rather low temperatures. In addition, the thermal stability of the CpTiCHT precursor is higher compared to the usually applied ALD precursors of Ti. The introduction of this new ALD precursor family offers a basis for further improving the ALD processes of group 4 oxide containing thin films for a wide range of applications

Electric and Magnetic Properties of ALD-Grown BiFeO₃ Films

The magnetization and electric polarization in thin bismuth ferrite films (BFO) films have been under extensive study for high technological potential of single-phase multiferroic materials. Surpassing the antiferromagnetic nature and weak magneto-electric coupling of bulk BFO has required highly specialized substrates and epitaxial growth methods so far. Polycrystalline single-phase multiferroic BFO (50–500 nm thick) films were grown by atomic layer deposition (ALD) on technologically simple Pt/SiO₂/Si substrates. The BFO films were found to exhibit strong saturating ferromagnetism and coercivity at temperatures ranging from cryogenic to room temperature even with 500 nm thick layers, a property which cannot be obtained with thick epitaxial films or bulk BFO. The magnetization mechanism was associated with magnetic domain wall dynamics and collapsing of the helimagnetic spin modulation. The electric properties were found to be strongly dependent on the film thickness. The film crystallization, composition, and chemical state have been analyzed by various techniques. The magnetic and ferroelectric properties were determined by using a SQUID magnetometer and a ferroelectricity tester. The results of the work indicate clearly that the ALD technique offers an efficient way for synthesis of polycrystalline BFO films and for tailoring their electromagnetic properties