Properties and high-pressure behavior of a ternary lead oxide Pb2MnO4

Pb2MnO4 and Sr-doped Pb2MnO4 powders have been synthesized along the Pechini process. Partial substitution of Pb2+ by Sr2+ has been effective up to 2 at.%. Beyond this value, secondary phases appeared among others PbO or SrMnO3. The effect of high pressures (<6 GPa) and high temperatures (<900 °C) on Pb2MnO4, containing Pb2+ cations with electron lone pairs, has been studied. In spite of the lone pairs present, this semiconductor (Eg = 1.5 eV) did not exhibit any phase transition under pressure. Instead, decomposition into three phases (Pb3Mn7O15, PbO and Pb3O4) has been observed with reduction of Mn4+ to Mn3+ and concomitant to oxidation of Pb2+ to Pb4+. Strontium doping, bearing no electron lone pair, turned out, however, to lead to the same decomposition, the one difference being a higher decomposition temperature. Electronic and thermal properties of pure and doped Pb2MnO4 were also investigated.

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