High pressure and high temperature synthesis and in-situ characterization of new compounds with special electronic transport properties, using "lone-pair" oxides, fluorides, sulphides and selenides of elements from groups 14-16

这项研究的目标是合成具有有趣的物理和电子传输性质的新型稳定结构。14？16族元素的氧化物、氟化物、硫化物和硒化物显示出单电子对的存在，使其成为研究的对象。这种化合物本质上提供了通过同时施加极端压力和温度来使自由电子对离域的机会。此外，这种位错与电子行为的变化有关，可能会引发输运性质的改变：绝缘体-金属类型和半导体-金属类型。在这种情况下，可以预见绝缘体-或半导体-金属-超导体的转变也是可能的。采用激冷式和原位式相结合的高压高温实验技术，利用大体积的多顶锤装置，将有助于发现这些新的有趣的相，并绘制它们在压力-温度-时间空间中的稳定范围。此外，对成为研究对象的化合物进行化学掺杂可能会加速离域过程和/或可以稳定在极端条件下获得的结构，并有助于在常压和温度下恢复它们。获得这种新相的手段是通过使用大容量的高压和高温设备，特别是多压头压力机(在我们的实验室和在德国汉堡的HASYLAB)提供的。可获得的压力和温度范围分别达到30 Gpa和2500°C。

The goal of the proposed study is to synthesize novel stable structures exhibiting interesting physical and electronic transport properties. The oxides, fluorides, sulphides and selenides of elements from groups 14¿16, which exhibit the presence of lone-electron pairs, are making the subject of the study. Such compounds offer intrinsically the opportunity to delocalize the free electron pair by simultaneous application of extreme pressures and temperatures. Furthermore, such dislocations are associated with changes in the electronic behaviour, likely to trigger modifications of the transport properties: insulator-metal, and semiconductor-metal type. In such circumstances, it is envisioned that an insulator- or semiconductor-metal-superconductor transition could be also made possible. A combination of quench-type and in-situ-type experimental high pressure and high temperature techniques employing large volume multianvil devices will be used to facilitate the uncovering of such new interesting phases, and to map their stability range in the pressure-temperature-time space. In addition, chemical doping of the compounds making the subject of the study could accelerate the delocalisation process and/ or could stabilise the structures obtained at extreme conditions and help retrieve them at ambient pressures and temperatures. The means of obtaining such new phases are provided by the use of large volume high pressure and high temperature devices, in particular multianvil presses (present both in our laboratory and at HASYLAB, DESY Hamburg). The range of attainable pressures and temperatures reaches 30 GPa and 2500 °C, respectively.