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The present study reports the thermal conductivity and electrical transport properties of Mo 2 Ga 2 C, which is the first member of double-A-layer MAX phases. Dense bulk samples of Mo 2 Ga 2 C were prepared by vacuum hot pressing. At room temperature, the thermal conductivity was measured to be 14.8 ± 1.0 W/(m•K) and the electrical resistivity was 0.525 ± 0.052 µ •m. Mo 2 Ga 2 C follows the Wiedemann-Franz law and the Lorenz number is 2.22×10 −8 W K −2 . Mo 2 Ga 2 C is a superconductor with a transition temperature of ca. 5.1 K (±0.1%). The thermal conductivity and electrical resistivity are lower than those of most MAX phases probably due to the extra Ga layer. IMPACT STATEMENTThe present study prepared dense bulk samples of Mo 2 Ga 2 C, the first member of double-A-layer MAX phases, and characterized the thermal conductivity and electrical transportation. The results indicated Mo 2 Ga 2 C to be a superconductor (T c = ∼ 5.1 K).

Near single phase ternary bulk thermoelectric material AgSbTe2 was synthesized by high pressure and high temperature (HPHT) method. The temperature-dependent thermoelectric properties including Seebeck coefficient, electrical conductivity, and thermal conductivity were studied. The HPHT synthesized AgSbTe2 sample has higher thermoelectric performance in the measured temperature range than that of the same sample prepared at normal pressure. The enhanced thermoelectric properties should be attributed to the HPHT quenching which keeps partially the high electrical conductivity of AgSbTe2 under high pressure.

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In this study, diamond crystals co-doped with boron and nitrogen were synthesized via a temperature gradient method at 5.3–5.8 GPa and 1300–1550 °C by adding B and N dopants to a system of carbon and an Fe-based solvent catalyst.