Morphology,Particle Size Control And Gas Sensing Properties Of Perovskite Structure ZnSnO₃

The nature of the gas sensitive material determines the performance of the gas sensor.ZnSnO₃is a ternary compound semiconductor material with good gas sensitivity.However,the operating temperature of a pure ZnSnO₃gas sensor is typically above 200?,which greatly limits its application.Therefore,how to reduce the operating temperature of ZnSnO₃gas sensor and make it have good gas sensitivity is a hot research topic in this field.Preparation of ZnSnO₃by high temperature dehydration of ZnSn(OH)₆is one of the ways to obtain such sensitive materials,and its properties are affected by microstructures such as morphology and particle size.During the synthesis of ZnSn(OH)₆,some organic functional additives affect its morphology and particle size.It has been shown that the micron-sized flower-like ZnSn(OH)₆synthesized by coprecipitation with triethanolamine(weak base)as an organic additive has the same morphology and particle size as the high temperature anhydrate ZnSnO₃,However,the gas sensitivity is poor,and the gas response is lower than 5 at 200?.In this paper,oxalic acid(weak acid)was used as an additive to synthesize nano-ZnSn(OH)₆cube.The high temperature anhydrate ZnSnO₃still has the same morphology and particle size.SEM and XRD analysis showed that oxalic acid could change the morphology,particle size and growth rate of ZnSn(OH)₆particles.SAED and TEM analysis showed that the synthesized ZnSn(OH)₆was polycrystalline,but its high temperature anhydrate ZnSnO₃was non-crystal.Mechanistic studies show that the crystal phase transition of polycrystalline ZnSn(OH)₆to amorphous ZnSnO₃is caused by a large number of oxygen vacancies formed during high temperature heat treatment,and these vacancies determine the gas sensing properties of ZnSnO₃.When the amount of oxalic acid added is 0.059 M for the synthesis of ZnSn(OH)₆precursor(denoted as ZSOH-0.059),the corresponding ZnSnO₃(denoted as ZSO-0.059)has the best gas sensitivity at 220?with UV irradiation.The gas sensitivity response to 500 ppm ethanol was as high as 147,and the response time and recovery time were 2 s and 60 s,respectively.Comparative analysis showed that the average particle size of ZSOH-0.059 cubic particles prepared under these conditions was the largest,and the high temperature dehydrated ZSO-0.059 band was the narrowest(3.19 e V).On the basis of the above studies,the nano-ZnSnO₃cube(denoted as ZSO-0.059)was modified with nano-TiO₂to lower its operating temperature.The experimental results show that when nano-TiO₂is 13 wt%,the nano-TiO₂@ZnSnO₃composite prepared under UV irradiation has a maximum gas-sensitive response of 94.3 in 500ppm ethanol gas(response time and recovery time are 3 s and 77 s),at which point the corresponding operating temperature is 80?.Obviously,in this way,the operating temperature of pure ZnSnO₃can be lowered and good gas sensitivity can be maintained.In summary,the morphological,particle size and growth rate of ZnSn(OH)₆were controlled by the functional additive oxalic acid.When the content of oxalic acid was suitable(0.059 M),the prepared ZnSnO₃had better gas sensitivity.The nano-TiO₂modification reduces its working temperature and maintains good gas sensitivity.