Study Of Novel All-Solid-State PH Sensors

pH is closely related to many fields and the determination of pH has been an indispensable process in these fields.Although the glass electrode pH sensor is used most widely,the shortcomings of fragility and limited measurement environment have become increasingly prominent.As a result,many new types of non-glass pH sensors have been widely studied in recent years.The solid electrolyte pH sensor can be used in high temperature and high pressure environment,with high mechanical strength and corrosion resistance.Metal/metal oxide pH sensor can be miniaturized and is resistant to high temperature and high pressure with high mechanical strength.Based on the above advantages of these two kinds of solid-state pH sensors,we prepared Y-doped barium zirconate ceramic pH sensor and Zr/ZrO₂pH sensor.We studied on the the preparation method and properties,and the main contents are as follows.?1?Y-doped barium zirconate powder was prepared by high temperature solid-state reaction and solution chemical method respectively,and the corresponding sintering properties were compared.The result shows that the sintering performance of the hollow spherical nano-powder solution prepared by chemical method is poor.In comparison,the powder particles synthesized by solid-state reaction are fine but with serious agglomeration,and need to be milled.In this work,we pulverize powders synthesized by solid-state reaction methods using two mechanical milling techniques:planetary milling and sand milling.It turns out that very small size and well-dispersed particles are obtained by sand-milling,obtaining a relative density as high as 99%with ultrafine grains sintered at a temperature of 1640 °C for 15h.The sintering condition is lower than those reported in literature and proton conductivity has been improved significantly.And preliminary studies on water vapor and ammonia gas sensing properties of densified Y-doped barium zirconate have been carried out.?2?A new type of ceramic pH sensor was prepared using Y-doped barium zirconate ceramics as the solid electrolyte.We studied the influence of different kinds of solid proton acid as inner references on the sensing performance of the sensors.It indicates that Y-doped barium zirconate ceramic pH sensor with phosphoric acid as the inner reference responded slowly but with high linear fitting and is in line with the linear relationship with the slope of-36.5 mV/pH.This sensor also shows rapid response under 80?,with high fitting but a drop in the slope.When using silicotungstic acid as the inner reference,we found that the ceramic sensor responded faster than that with phosphoric acid as the inner reference,with high fitting of up to 99.18%.This result is also in accordance with the linear relationship and the slope is-29.44 mV/pH.?3?Different Zr/ZrO₂pH sensors were prepared by high temperature oxidation method and electrochemical oxidation method.We also studied the differences of performance among sensors by adjusting the preparation conditions of different methods and different conditions.The sensor showed best performance with molten Na2CO3 as the oxidizing agent using high temperature oxidation method with very stable response value and high liner fitting,and the slope is-28.16mV/pH.When prepared by anodic oxidation method,we studied the effect of organic electrolyte and inorganic electrolytes on the nanostructure of surface oxide film.When using inorganic electrolyte with the oxidation time for 1 h for the second step oxidation,we found high linear fitting and the slope was-31.51 mV/pH at pH range of 1.68¹2.47.