Thermochemical Mechanism of Optimized Lanthanum Chromite Heaters for High-Pressure and High-Temperature Experiments

High-pressure heaters in large volume presses must reconcile potentially contradictory properties, and the whole high-pressure and high-temperature (HPHT) community has been engaged for years to seek a better heater. LaCrO3 (LCO)-based ceramic heaters have been widely applied in multianvil apparatus; however, their performance is far from satisfactory, motivating further research on the chemical optimization strategy and corresponding thermochemical mechanism. Here, we adopted a chemical-screening strategy and manufactured tubular heaters using the electrically, chemically, and mechanically optimized Sr-Cu codoped La0.9Sr0.1Cr0.8Cu0.2O3-δ (LSCCuO-9182). HPHT examinations of cylindrical LSCCuO-9182 heaters on Walker-type multianvil apparatuses demonstrated a small temperature gradient, robust thermochemical stability, and excellent compatibility with high-pressure assemblies below 2273 K and 10 GPa. Thermochemical mechanism analysis revealed that the temperature limitation of the LSCCuO-9182 heater was related to the autoredox process of the Cu dopant and Cr and the exchanging ionic migration of Cu and Mg between the LSCCuO-9182 heater and the MgO sleeve. Our combinatorial strategy coupled with thermochemical mechanism analysis makes the prioritization of contradictory objectives more rational, yields reliable LCO heaters, and sheds light on further improvement of the temperature limitation and thermochemical stability.

大容量压机中的高压加热器必须协调可能相互矛盾的性能，整个高温高压（HPHT）领域多年来一直致力于寻找更好的加热器。基于LaCrO₃（LCO）的陶瓷加热器已广泛应用于多砧装置；然而，它们的性能远不能令人满意，这促使人们进一步研究化学优化策略和相应的热化学机制。在此，我们采用了一种化学筛选策略，并使用电学、化学和力学性能优化的Sr - Cu共掺杂La₀.₉Sr₀.₁Cr₀.₈Cu₀.₂O₃ - δ（LSCCuO - 9182）制造了管状加热器。在Walker型多砧装置上对圆柱形LSCCuO - 9182加热器进行的高温高压检测表明，其温度梯度小，热化学稳定性强，在2273 K和10 GPa以下与高压组件具有良好的兼容性。热化学机制分析表明，LSCCuO - 9182加热器的温度限制与Cu掺杂剂和Cr的自身氧化还原过程以及LSCCuO - 9182加热器和MgO套管之间Cu和Mg的交换离子迁移有关。我们的组合策略与热化学机制分析相结合，使相互矛盾目标的优先级确定更加合理，生产出可靠的LCO加热器，并为进一步提高温度限制和热化学稳定性提供了思路。