Ceramic nanoparticles play a critical role in high-temperature applications, particularly in solid oxide fuel cells (SOFCs). Among these, lanthanum chromite (LaCrO₃) stands out as a key material for interconnects due to its stability in both oxidizing and reducing atmospheres, excellent electrical conductivity, and thermal expansion compatibility with other cell components. Unlike zirconia-based electrolytes, which primarily function as oxygen ion conductors, LaCrO₃ serves as a conductive ceramic interconnect, ensuring electrical continuity between adjacent cells while preventing fuel and oxidant mixing.

The Pechini method is a widely adopted synthesis route for producing LaCrO₃ nanoparticles with controlled stoichiometry and particle size. This process involves the formation of a polymer-metal ion gel through the reaction of metal nitrates with citric acid and ethylene glycol. The chelation of metal ions by citric acid prevents premature precipitation, ensuring homogeneity. Upon heating, the gel undergoes polyesterification, forming a rigid polymer network that immobilizes the metal ions. Subsequent calcination at elevated temperatures, typically between 800°C and 1000°C, decomposes the organic matrix and yields phase-pure LaCrO₃ nanoparticles. The Pechini method offers advantages such as excellent compositional control, uniform particle size distribution, and scalability, making it suitable for industrial applications.

Electrical conductivity is a defining property of LaCrO₃ interconnects. The material exhibits p-type semiconducting behavior under oxidizing conditions due to the formation of electron holes via chromium oxidation (Cr³⁺ → Cr⁴⁺). Doping with divalent cations such as strontium (Sr²⁺) or calcium (Ca²⁺) at the lanthanum site enhances conductivity by increasing charge carrier concentration. For instance, La₀.₈Sr₀.₂CrO₃ demonstrates a conductivity of approximately 40 S/cm at 800°C in air, which is sufficient for SOFC interconnect applications. In reducing atmospheres, conductivity decreases due to the loss of hole carriers, but the material retains sufficient performance to maintain cell operation. The dual-atmosphere stability of LaCrO₃ is a key advantage over metallic interconnects, which suffer from oxidation and chromia scale formation.

Thermal expansion matching is another critical requirement for SOFC interconnects. Mismatched coefficients of thermal expansion (CTE) between components can lead to mechanical stress, delamination, or cracking during thermal cycling. LaCrO₃ exhibits a CTE of approximately 9.5–11 × 10⁻⁶ K⁻¹, which closely matches that of yttria-stabilized zirconia (YSZ) electrolytes (10–11 × 10⁻⁶ K⁻¹) and other common SOFC materials. Doping strategies can further fine-tune the CTE; for example, substituting chromium with cobalt or iron increases the CTE slightly, while magnesium doping reduces it. This tunability ensures compatibility with adjacent cell layers over a wide temperature range, typically from room temperature to 1000°C.

Unlike zirconia-based electrolytes, which rely on oxygen ion transport, LaCrO₃ interconnects function as electronic conductors. YSZ and related materials, such as gadolinia-doped ceria (GDC), are ionic conductors with negligible electronic conductivity. Their primary role is to separate the anode and cathode while facilitating oxygen ion migration. In contrast, LaCrO₃ interconnects provide electrical connection between cells in a stack without participating in electrochemical reactions. This distinction is crucial for SOFC design, as interconnects must prevent gas crossover while maintaining low ohmic losses.

The stability of LaCrO₃ under SOFC operating conditions is superior to that of alternative interconnect materials. Metallic alloys, such as ferritic stainless steels, are susceptible to chromia scale formation, which increases electrical resistance and can poison cathode materials. LaCrO₃, however, forms no resistive scales and maintains stable performance over long durations. Its chemical inertness prevents reactions with adjacent components, ensuring long-term durability. Additionally, the material’s high melting point (>2400°C) and mechanical strength contribute to its reliability in harsh environments.

Processing challenges associated with LaCrO₃ include sintering difficulties due to its refractory nature. Achieving dense interconnect layers often requires high sintering temperatures (>1400°C) or the use of sintering aids such as transition metal oxides. The Pechini method mitigates some of these issues by producing nanoparticles with high surface area, which enhances sinterability. Advanced techniques like spark plasma sintering (SPS) have also been explored to achieve dense LaCrO₃ at lower temperatures.

In summary, lanthanum chromite nanoparticles are indispensable for SOFC interconnects due to their balanced electrical conductivity, thermal expansion compatibility, and chemical stability. The Pechini method enables precise synthesis of these nanoparticles, ensuring optimal performance in high-temperature environments. While zirconia-based electrolytes focus on ionic conduction, LaCrO₃ serves a distinct role as an electronic conductor, bridging individual cells in a stack without compromising structural integrity. Its superiority over metallic interconnects in terms of stability and durability makes it a material of choice for advanced SOFC systems. Continued research into doping strategies and processing techniques will further enhance the performance and applicability of LaCrO₃ in next-generation fuel cells.