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.