Bulk conductance sensor

SrTi03 may serve as a well-investigated material for such a bulk conductivity sensor. Its defect thermodynamics and also the relevant kinetic parameters have been discussed in detail in Part I.2 In particular at low temperatures and at small sample thicknesses L, the kinetics of oxygen incorporation becomes surface reaction controlled, and ks the decisive kinetic parameter. 

Important advantages of the bulk conductivity sensor are, besides selectivity, its simplicity (no reference needed) and its selectivity an important drawback is the T-dependence which can be quite significant (see above). Improvement via doping or by using a T-reference is straightforward, but partly at the cost of sensitivity, simplicity, or range of application. 

Obviously, high D5 values, e.g., as required for bulk conductivity sensors, demand materials that are free from redox centers, while the minimization of drift phenomena in boundary layer sensors demands just the opposite.239... 

Dq is not negligible [446]. In complete contrast to the bulk conductivity sensors, redoxactive impurities may now be of considerable advantage (see Section 6.6.1). The third type of sensor, in which a pure ion conductor is used, is the EMF sensor (potentiometric sensor), as represented by the A-probe, dealt with in detail in Section 7.2. Again, only local equilibrium is set up there (see Table 7.2), thus, in the oxide V/xo 0, but now conversely = 0 Vpe- (see previous section). Here... 

An acid-base bulk conductivity sensor implies the dissolution of complex gases and, hence, the diffusion of two types of ions or of the neutral species itself. In principle, hydrates or water-dissolving perovskites come into question for the detection of water (cf. Chapter 5) and ammoniates for the detection of NH3. On account of the kinetic difficulties (cf., for instance, Section 6.5) here it is necessary to... 

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