Innovative new High-Pressure Oxotellurate Compounds

New, innovative materials that enable increased miniaturization of electrical devices or guarantee higher memory densities are key components for the future of mankind. In this context, the rate of general progress depends heavily on our ability to create new materials. In the solid state, material synthesis usually requires high temperatures. As a result, only the most thermodynamically stable compounds are accessible by such a route. However, by changing the external parameter of pres- sure, other metastable phases are possible to produce, which would not be achievable by conven- tional synthesis at ambient pressure. This project involve a systematic investigation of oxotellurate compounds under high-pressure/high- temperature (HP/HT) conditions, synthesizing and characterizing potential new materials. The diver- sity of the oxotellurate compounds studied here is due to the high number of possible different crys- tal structures, for which a particular electronic situation at the tellurium atoms is responsible. Re- cently, novel transition metal orthotellurates M3TeO6 (M = Ni, Co, Mn) have gained great importance due to their multiferroic properties. These are substances that have several order states and by vary- ing one state, the second can be influenced. Thus, by means of an electric field, the magnetism of the material can be changed and vice versa. Recently, we succeeded in synthesizing a high-pressure mod- ification of Co3TeO6, which has the same highly interesting structure type as Ni3TeO6 and thus could exhibit comparable multiferroic properties. The research field of high-pressure/high-temperature chemistry of oxotellurates is still in its infancy. We successfully use a combination of precursor compounds followed by multianvil HP/HT experi- ments. With our facility, conditions inside the sample capsule of 1400 C and 140,000 bar are achiev- able. The Multianvil method is an ideal compromise between maximum achievable quasi-hydrostatic pressure and sample size, which subsequently allows comprehensive analysis. By the way, the term multianvil means that the sample is compressed uniformly from several sides by anvils. The basis of all further investigations is then the structural elucidation of the new compounds and crystal struc- tures using X-ray diffraction. The additional synthesis parameter of pressure makes these investigations unique. On the one hand, it is a synthesis technique that can even be used industrially, as the synthesis of artificial diamond shows. On the other hand, this method uses conditions that prevail in deep layers of the earth, to which mankind does not yet have access and therefore depends on such experiments to gain a deeper understanding.