The transport of protonic charge carriers along and within the pore surfaces of porous oxide matrices is of significant importance for many catalytic and electrochemical applications, with porous TiO₂ being a candidate material both for photocatalytic applications and as an electronically conducting support for polymer-based electrochemical cells. This work investigates the effect of acceptor (Cr and Fe) and donor (Nb) doping on protonic surface conduction in porous TiO₂ over a wide range of relative humidity, temperature and oxygen activity. Generally, we find that acceptor dopants on the surface counteract dissociation and reduce the mobility of protons, while donor dopants give rise to enhanced dissociation making protonic surface conduction the highest for donor-doped samples, contrary to conventional bulk proton conductors. Moreover, protonic surface conduction in Cr-doped TiO₂ is significantly higher under oxidising conditions compared to reducing conditions, which we relate to the presence of a higher valent species such as Cr⁶⁺ on the surface under oxidising conditions, again emphasising that protonic surface conduction increases with higher-valent (donor) and more acidic cations present on the surface.

Stereolithography is a layer-by-layer building fabrication technique enabling production of advanced ceramic 3D shapes that are not achievable by other methods. Critical parameters of stereolithography are associated with the preparation of a ceramic resin exhibiting suitable rheological and optical properties, as well as tunable curing property to achieve the desired level of resolution of complex 3D parts. However, tailoring the cure depth for each layer is challenging for functional ceramics due to their high refractive index giving increased light scattering. Here, the stereolithography 3D printing of BaTiO₃ ceramic resins is investigated by employing a desktop 3D printer (λ = 405 nm) and a commercial base resin. The effects of two BaTiO₃ powders with different size distributions (one micro-sized powder with grains in the range 1–20 µm, and one agglomerated nano-sized powder in the range 60–100 nm), on the viscosity and curing characteristics of the ceramic resins were investigated. It is shown that the nano-sized powder resulted in increased viscosity, increased scattering, and reduced cure depth compared to the micro-sized BaTiO₃ ceramic resin. In general, the cure depth decreased with increasing ceramic loading. Successful prints were obtained for an overcuring of at least 40% between layers to assure good adherence between the layers. The printing properties of the ceramic resins from both powders were suitable for printing green parts with 50 µm layer thickness.

Thin-film piezoelectrics are widely investigated for actuators and energy harvesters, but there are few alternatives to toxic lead zirconate titanate. Biocompatible Ca- and Zr-modified BaTiO₃ (BCZT) is one of the most promising lead-free alternatives due to its high piezoelectric response. However, the dielectric/piezoelectric properties and structural integrity of BCZT films, which are crucial for their applications, are strongly influenced by the substrate upon which the film is grown and the related processing methods. Here, the in-plane stress, microstructure, dielectric, and piezoelectric properties of 100–500 nm thick high-temperature RF-sputtered BCZT films on industrially relevant Si-based substrates were investigated. Obtaining polycrystalline piezoelectric films required deposition temperatures ≥ 700 °C, but this induced tensile stresses of over 1500 MPa, which caused cracking in all films thicker than 200 nm. This degraded the dielectric, piezoelectric, and ferroelectric properties of films with larger electrode areas for applications. Films on SrTiO₃, on the other hand, had a compressive residual stress, with fewer defects and no cracks. The grain size and surface roughness increased with increasing deposition temperature. These findings highlight the challenges in processing BCZT films and their crucial role in advancing lead-free piezoelectric technologies for actual device applications.

Direct fuelling of solid oxide fuel cells with ammonia is attractive but can lead to reduced stack durability due to nitridation of the metallic interconnect material. This works investigates the stability of the interconnect material Crofer 22 APU in ammonia-containing atmosphere and evaluates the effects of pre-oxidation and the application of nickel or yttrium coatings to mitigate nitridation. Exposures were conducted in dry and wet NH3-H2-N2 mixtures at 650 °C and 750 °C and 20 bar for up to 800 h. Bare Crofer 22 APU suffered from nitridation under all exposure conditions with more severe degradation observed at 650 °C compared to 750 °C and in dry conditions. At 750 °C, pre-oxidation and Y coating both provided excellent resistance against nitridation in wet conditions, while these treatments had no effect in dry conditions. A Ni coating provided best protection in dry conditions and at 650 °C although it did not completely supress nitridation.

Ammonia is emerging as a promising carbon-free fuel that can be converted to energy using combustion engines and fuel cells or converted to hydrogen in a cracker. The structural alloys in these applications are exposed to harsh conditions, notably high temperature and presence of NH ₃ and H ₂ O, under which their behavior remains insufficiently understood. In this work, the nitridation behavior of seven alloys (625, 600, 800HT, AISI 316L, AISI 310S, AISI 444 and EF101) was systematically studied as a function of temperature (495–670 °C), NH ₃ concentration (6–85%) and H ₂ O content (0–2%). Mass gain measurements combined with microstructural characterization were used to quantify nitridation and identify degradation mechanisms. Nitridation resistance increased with decreasing Fe-content and increasing Ni-content of the alloy, with alloy 625 showing the highest resistance across the investigated conditions. Increasing temperatures and the presence of 2% H ₂ O accelerated nitridation in alloys 600, 800HT and 316L, but suppressed it in alloy 444. The improved nitridation resistance of alloy 444 is attributed to the formation of a protective oxide scale, highlighting the critical interplay between oxidation and nitridation in environments containing both NH ₃ and H ₂ O.