BaFe1-xTaxO3-y - a material for temperature independent resistive oxygen sensors?

氧传感器用于控制燃烧过程和呼吸分析。电阻传感原理，其中传感材料的电导率随氧含量而变化，可以是可替代的探针。这种传感器可以在陶瓷平面技术中非常好地小型化。尽管人们已经尝试利用平面电阻式氧传感器的优点，但是迄今为止主要由于传感器信号的温度依赖性结合长期不稳定性和对传感器中毒组分的不稳定性以及由于低灵敏度而失败。在过去的十年中，p型导电系统SrTi_（1-x）Fe_xO_（3-y）（STF）已被详细研究，因为其导电性在感兴趣的范围内具有与温度无关的氧浓度依赖性。它的行为已被解释为缺陷化学。然而，STF的缺点是低灵敏度和在排气中的低稳定性。几乎未知的是材料BaFe 1-xTaxO 3-y（BFT）。申请人的第一次初步研究证实了几乎与温度无关的电导率，同时，与STF相比，灵敏度高出25%。此外，即使在几乎400 °C的温度下，也可以使用合适的钽含量来操作传感器，并保持与温度无关的特性。因此，我们甚至可以构建适合于移动的呼吸测量的氧传感器。该项目有两个主要目标。在项目的一部分（约占项目的3/4）中，我们将从根本上了解更多关于材料BFT（钽含量在10%和50%之间）的信息。这包括确定第一个缺陷的化学常数和电子输运参数，以及通过适当的测试，在BFT的氧扩散系数的估计。在工程科学为导向的项目（约1/4的项目范围）的一部分，温度无关的电阻式氧传感器将在其性能方面的特点。在这里，对预期的传感器中毒化合物的行为是感兴趣的。在该项目部分中，可以使用现有的传感器（基板加加热器，盖和电极），因此不必花费太多时间。

Oxygen sensors are required for the control of combustion processes and for breath analysis. The resistive sensing principle, in which the conductivity of the sensing material changes with the oxygen content, can be an alternative to the lambda-probe. Such sensors can be miniaturized very well in ceramic planar technology. Although one has tried to exploit the advantages of planar resistive oxygen sensors, one has failed so far mainly due to the temperature dependence of the sensor signal in combination with long-term instabilities and instabilities against sensor poisoning components and as well as due to a low sensitivity. In the past decade, the p-type conducting system SrTi1 xFexO3-y (STF) has been studied in detail since its conductivity features a temperature independent oxygen concentration dependence in the range of interest. Its behavior has been explained by defect chemistry. A disadvantage, however, is the low sensitivity of STF and the low stability in the exhaust.Almost unknown is the material BaFe1-xTaxO3-y (BFT). Very first preliminary investigations of the applicant confirmed an almost temperature-independent conductivity and, at the same time, a 25% higher sensitivity compared to STF. Moreover, it appears feasible to operate sensors with a suitable tantalum content even down to almost 400 °C and to conserve the temperature-independent characteristic. Hence, one may even build an oxygen sensor which is suitable for mobile breath measurement.The project has two main goals.In one part of the project, which accounts for about 3/4 of the project, we will fundamentally learn more about the material BFT (with a tantalum content between 10 and 50%). This includes determining first defect-chemical constants and electronic transport parameters as well as the estimation of the oxygen diffusion coefficients in BFT by appropriate tests.In an engineering science oriented part of the project (about 1/4 of the project scope) temperature-independent resistive oxygen sensors will be made and characterized in terms of their properties. Here, the behavior against expected sensor poisoning compounds is of interest. In this project part, existing transducer can be used (substrate plus heater, cover and electrodes) so that not too much time has to be spent for that.