The roles of interstitial oxygen and phase compositions on the thermoelectric properties CuCr0.85Mg0.15O2 delafossite material

Highlights: • Phase composition and interstitial oxygen control thermoelectric properties of CuCr_0.85Mg_0.15O₂. • Native interstitial oxygen is induced during the CuCrO₂ phase formation. • Samples sintered at 1273 and 1673 K have the same Seebeck coefficient but different conductivity. • High conductivity of the 1673 K sample originated from the low percentage of CuO phase and the appearance of Cu₂O phase. • Seebeck coefficient of samples depends on component phases but its behavior follow Heikes or Pysarenko law by defect-type. -- Abstract: In this work, role of phase composition and interstitial oxygen on the thermoelectric properties of CuCr_0.85Mg_0.15O₂ materials prepared at different sintering temperatures (1273–1673 K) for short time (3 h) are reported. Interestingly, the samples sintered at 1273 K and 1673 K had the same Seebeck coefficient, despite the 1273 K sample having significantly lower conductivity, which are discussed via phase composition and interstitial oxygen induced during the CuCrO₂ phase formation and its related defect (V_Cu, V_Cr, …). Besides, high conductivity of the 1673 K sample originated from the low percentage of CuO phase and the appearance of Cu₂O phase. Since the 1273 K and 1673 K sintered samples have almost the same percentage of delafossite and spinel phases so the 1673 K sample still remain its high Seebeck coefficient. We suggest some reaction chemical equations for elucidating the roles of interstitial oxygen on the phase composition and thermoelectric properties CuCr_0.85Mg_0.15O₂ delafossite material.