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Potencjometryczny sensor chloru

Dziubaniuk M., Janora S., Pasierb P., Rękas M.

Pomiary Automatyka Kontrola

2010

R. 56, nr 6

525-528

Do konstrukcji sensora chloru wybrano tlenochlorek lantanu, LaOCl, jako elektrolit stały. Jego warunki preparatyki określono metodą analizy termicznej oraz dyfrakcji promieniowania rentgenowskiego. Mikrostrukturę spieku elektrolitu określono przy użyciu mikroskopii elektronowej. Charakterystykę sensora wyznaczono dla koncentracji chloru w powietrzu w zakresie 0-100 ppm. Skonstruowany sensor pracuje poprawnie i jest stabilny w zakresie temperatur 500 - 800°C. Wyznaczona zależność napięcia źródłowego ogniwa od koncentracji chloru jest zgodna z prawem Nernsta dla n=2.

A chlorine gas sensor was fabricated with the Cl- ion conducting lanthanum oxy-chloride, LaOCl, a solid electrolyte. Preparation conditions, especially the optimal calcination temperature, were determined by means of the differential thermal analysis (DTA), thermogravimetry (TG) as well as mass spectrometry (MS). According to the x-ray diffraction (XRD) analysis, the product was homogenous and crystallized in tetragonal P4/nmm structure. Scanning electron microscopy (SEM) revealed that it is composed of uniform grains of the 210-260 nm dimension. The sensor manu-facture consisted of several steps. Firstly, the powder of LaOCl was pressed in pellet die (100 MPa) and calcined at 700°C for 2 hours. Then, both sides of polished pellet were covered with Pt paste. It was fired at 1100°C for 2 hours after cooling down the pellet was attached to Al2O3 tube using the ceramic binder to allow the separation of both electrode compartments during the sensor operation. The device was dried and heated at 370°C. The electromotive force (EMF) of the constructed cell was measured asa function of temperature (400- 800°C), Cl2 concentration in air (0-100 ppm) at sensing electrode and time. Air with constant concen-tration of chlorine (100 ppm) gas atmosphere was kept at reference electrode. The sensor exhibited reliable, stable and reproducible signal at operation temperature between 500 - 800°C. The deter-mined EMF vs. logp(Cl2) dependence may be described by the Nernst law for n= 2.