Langasite SAW device with gas-sensitive layer

High temperature langasite SAW oxygen sensors using ZnO as a resistive sensing layer were fabricated and tested in a wired configuration up to 650°C, representing an important step toward future high temperature wireless sensor development. ZnO layers deposited by spin coating and RF sputtering methods were compared. The langasite SAW sensor with spin coated ZnO sensing film had strongly increasing surface wave attenuation from 100°C to 250°C and undetectable reflections above 250°C. The langasite SAW gas sensor with sputtered ZnO sensing film showed clear oxygen gas flow response from 500°C to 650°C.