REECa4O(BO3)3 (REECOB): New material for high-temperature piezoelectric applications

Abstract

Especially in terms of the modern environmental consciousness with demand for more efficient, cleaner and more ecological machinery, processes has to be improved. This is mainly essential for combustion engines, coal fired electrical plants as well as gas heating installations etc. Processes have to be measured and controlled in situ in order to increase efficiency by manipulating parameters. Doing so, sensors which can resist and work under high temperature/high pressure conditions are strongly required. Unfortunately, most piezoelectric sensor materials known today (like quartz, Bi4Ti3O12-and PZT-ceramics) can not proceed at elevated temperatures above 600°C. Others that can, are either expensive and energy-consuming in production (GaPO4) or only available in sufficient size as naturally occurring minerals (tourmaline) with fluctuating properties. In the last few years, the new material REECOB (REECa4O(BO3)3 with REE = rare earth elements: Gd, Y, La, Sm, Nd) emerged to be a promising candidate for high temperature applications, displaying constant piezoelectric properties up to 1,200°C. This material has made a steep career in optical applications (laser host material, nonlinear optics) since the mid-1990s but good properties for sensing applications are only known for a few years (Shimizu et al. 2004; Markiewicz et al. 2006). Investigations on ultra high temperature properties are relatively new (Zhang et al. 2008a, b, c). Unfortunately, thermomechanical data of the material are very rare and partially contradictional.