Thermoelectric properties and stability characterization of doped-LaCrO3/Al2O3 composites for high-temperature thermocouples

Electroceramics-based thick film thermocouples were developed for accurate temperature monitoring in harsh environments, utilizing doped LaCrO 3 perovskite ceramics known for their chemical stability and thermoelectrical properties at high temperatures. LaCrO 3 (LC), La 1–x Sr x CrO 3 (LSC x ), La 1–x Ca x CrO 3 (LCC x ), and La 0.8 Sr 0.2 Cr 1-x Mn x O 3 (LSCM x ) (0.1 ≤ x ≤ 0.3) compositions were investigated and printed on Al 2 O 3 substrates. Thermoelectric characterization in air up to 900 °C revealed intrinsic Seebeck coefficients ranging from 150 μV/K to 380 μV/K for variable substitution levels of Sr, Ca, and Sr/Mn-doped lanthanum chromites . The fabricated thermocouples exhibited stable, linear, and reproducible temperature-dependent thermoelectric voltage responses. The most sensitive thermocouples were LC//LCC30 and LC//LSC30 showing effective Seebeck coefficients of 222.32 μV/K and 201.10 μV/K, respectively. Composites of LC and doped-LC with Al 2 O 3 were synthesized to enhance sinterability and long-term stability. XRD and XPS analyses revealed low-level formation of secondary phases and new solid solutions due to high-temperature reactivity. Electrical conductivity decreased with Al 2 O 3 content, and thermoelectrical voltage for LCC30–Al 2 O 3 //LC–Al 2 O 3 couples exhibited good linear responses and high sensitivities, with effective Seebeck coefficients ranging from 230.34 μV/K to 255.21 μV/K for Al 2 O 3 volume fractions between 10% and 30%, respectively. These experiments demonstrate the potential of "all-ceramic" thermocouples for monitoring temperature in extreme conditions as an alternative to precious metal thermocouples. • Observed inverse correlation between Seebeck coefficients and cation concentration in LaCrO 3 . • Fabrication of novel all ceramic thick film thermocouples. • LC//LCCx thermocouples tested, achieving max output of ∼140 mV. • Improved thermoelectric properties by adding alumina, lowering conductivity, boosting intrinsic Seebeck. • Findings signal potential for high-performing all-ceramic thermocouples.