Mixed conductivities of A-site deficient Y, Cr-doubly doped SrTiO3 as novel dense diffusion barrier and temperature-independent limiting current oxygen sensors

Abstract A-site-deficient Y, Cr doubly doped SrTiO3 ((Y0.08Sr0.92)1-xTi0.8Cr0.2O3−δ (x = 0.01, 0.03, 0.05)) powders were synthesized via sol–gel method, followed by sintering at 1450 °C at ambient condition. The phase composition, mixed conductivities, and sensing performance are characterized to identify the influence of A-site deficiency on the Y- and Cr-doubly doped SrTiO3. The ionic conductivity and total conductivity of (Y0.08Sr0.92)1-xTi0.8Cr0.2O3−δ clearly increase and decrease upon an increase in the A-site deficiency, respectively. The enlarged saddle point and decreased relaxation time are responsible for the augmentation of ionic conductivity. The oxygen sensor with (Y0.08Sr0.92)1-xTi0.8Cr0.2O3−δ dense diffusion layer show superior sensing performance with A-site deficiency level increasing. The relationship between logIL and 1000/T is obtained and the charge compensation mechanism is systematically discussed. The obtained results demonstrated that limiting current is nearly independent of temperature at high operating temperature. This paper provides a chemical strategy to enhance the mixed conductivity of oxygen sensors through Y- and Cr-double doping and via a simple, low cost, and traditional sol–gel technique.