The gauge factor (GF) of a resistor is defined as the ratio of the relative change in resistance ( R/R) and the strain ( l/ l). The GFs of thick-film resistors are generally between 3 and 15. Due to their stability, a temperature coefficient of resistivity (TCR) under 100 × 10−6/K and their relatively low cost, strain gauges using thick-film technology offer advantages, in some applications, over both metal films (low GF, low TCR, expensive) and semiconducting elements (high GF, high TCR, inexpensive) [1, 2]. Within the same resistor series, both the GFs and the current-noise indices of thick-film resistors increase with increasing sheet resistivity [3, 4]. Therefore, in most cases 10 kohm/sq. resistors are used for the strain sensors as a useful compromise between sensitivity and relatively low noise. Pressure or force sensors can be made with resistors on deformable membranes. Thick-film resistors are printed and fired on a ceramic substrate (diaphragm), which is usually based on alumina. However, sensing elements made on partially stabilized tetragonal zirconia would exhibit some improved characteristics, as tetragonal zirconia has a higher mechanical strength and a lower modulus of elasticity than alumina [5]. This means that for the same thickness of ceramic membrane the operating range will be extended. This is shown schematically in Fig. 1a and b for a diaphragm with free edges and with fixed edges, respectively. The deformation of Al2O3-based and tetragonal ZrO2-based membranes was calculated using the following parameters: membrane radius, 20 mm; thickness, 0.635 mm; and pressure, 1.5 × 104 Pa. Some mechanical characteristics for 96% Al2O3, which is normally used for the substrates of thick-film circuits, and for tetragonal ZrO2 (Y-TZP−Y2O3 stabilized tetragonal zirconia) are summarized in Table I. Thick-film resistor materials are a complex mixture of conductive particles, glass phase and oxide modifiers. During firing, all the constituents of the resistor material react with each other and also with the ceramic substrate [6–9]. As thick-film resistors were developed for firing on alumina substrates, their compatibility and possible interactions with ZrO2 have to be evaluated. TABLE I Some characteristics of 96% Al2O3 and Y-TZP (tetragonal ZrO2)