Experimental investigation of the BAW device potentials of singly rotated Y-cut ordered Langasite-structure crystals

This paper discusses the results from two rounds of experimental mapping (with gross and refined incremental cut angle) for BAW device potentials of singly rotated Y-cut plates of the ordered Langasite-structure compounds CNGS, CTGS, SNGS, and STGS. Identical groups of singly rotated Y-cut plano-plano test resonators were fabricated with cut angles ranging from -60° to +60° at 15° and 3° increments. Room temperature equivalent circuit parameters and normalized frequency versus temperature were measured and compared. The data collected are examined in term of three primary factors for BAW device potentials, namely, the electromechanical coupling strength, the acoustic loss (or the Q·f product), and the existence of temperature compensated orientation. The results are also compared with a group of AT-cut quartz references of the same design. As anticipated, based on the order-disorder physical arguments, strong electro-mechanical coupling strength (more than 4 times that of AT) and low acoustic loss (in one CNGS case the highest Q·f product reaches 3.8 times that of AT, higher even than the best reported for Langatate) were observed.