Preparation And Physical Properties Of XSnO₃（X=Zn,Mg）

XSnO₃（X=Zn,Mg）are direct and wide band-gap semiconductor materials with ilmenite type structure.These kinds of materials have great application prospect in electronic devices and other fields due to their rich properties,such as ferroelectric,dielectric,piezoelectric,optical,and these materials are rich in element reserves and environmentally friendly.However,XSnO₃（X=Zn,Mg）have a variety of problems that are difficult to solve,such as thermal stability,and these problems were not fully recognized by many scholars,so the researches on this kind of materials were still less,and even some of them were mistakes.In this paper,XSnO₃（X=Zn,Mg）thin films,powders and bulks were prepared by sol-gel spin coating method and precipitation method,The phases,surface morphologies,optical and electrical properties were systematically studied,and some problems existing in previous literatures were clarified.The details are as follows.First of all,we have tried to prepare Zn SnO₃films by sol-gel spin coating method.However,the final samples were all the mixture of Zn₂SnO₄and SnO₂,and Zn SnO₃phase was not found at different pyrolysis and calcination temperatures.Then,the precipitation method was used to try to prepare Zn SnO₃powders.The results of XRD,Raman and TG-DSC show that the amorphous Zn SnO₃was obtained when the calcination temperature only was 300℃.With the increase of the calcination temperature,the Zn SnO₃began to decompose into a mixture of Zn₂SnO₄and SnO₂.The above results show that Zn SnO₃is a pressure-stable material,which is difficult to be successfully prepared by conventional sol-spin coating method or precipitation method.Secondly,the structural instability of Zn SnO₃was analyzed based on the structural tolerance factor of ilmenite type,and the structural stability of XSnO₃with ilmenite structure were further investigated.The calculated results show that,Mg SnO₃has better thermal stability than Zn SnO₃.The result points the way to further research.Thirdly,the single-phase Mg SnO₃films were prepared by sol-gel spin coating method.The surface morphologies,optical and ferroelectric properties of these samples were tested and analyzed.The results show that the ferroelectric property of Mg SnO₃films was poor at room temperature.Therefore,Mg SnO₃bulks were prepared by precipitation method,and the phase transition behavior of Mg SnO₃bulks was analyzed by its dielectric constant-temperature spectroscopy.The results show that the room temperature is the temperature of ferroelectric-paramoelectric transition of Mg SnO₃,which explained the reason for the poor ferroelectric performance of Mg SnO₃thin films at room temperature.Finally,Mg SnO₃films with（104）crystal-plane preferential growth were prepared by sol-gel spin coating method by controlling the concentration of precursor sol.The effects of the concentration of precursor sol on（104）crystal-plane preferential growth state,optical and ferroelectric properties of Mg SnO₃thin films were studied.In conclusion,it was clarified that Zn SnO₃is a pressure-stable material and it is difficult to successfully prepare Zn SnO₃with good crystallization by conventional methods by this paper.Then,based on the calculated results of tolerance factor,Mg SnO₃was selected as the subject of study.And then,Mg SnO₃thin films and bulks with good crystallization were prepared by sol-spin coating method and precipitation method.The effects of the preparation parameters on the optical and electrical properties of Mg SnO₃were systematically studied,and the Mg SnO₃thin films with preferential orientation were prepared.The above studies laid a foundation for the further research and application of Mg SnO₃in various electronic devices and other fields.