title: Applicability of LiNbO3, langasite and GaPO4 in high temperature SAW sensors operating at radio frequencies.
abstract: The applicability of LiNbO3, langasite and GaPO4 for use as crystal substrates in high temperature surface acoustic wave (SAW) sensors operating at radio frequencies was investigated. Material properties were determined by the use of SAW test devices processed with conventional lithography. On GaPO4, predominantly surface defects limit the accessible frequencies to values of 1 GHz. Langasite SAW devices could be operated up to 3 GHz; however, high acoustic losses of 20 dB/micros were observed. On LiNbO3, the acoustic losses measured up to 3.5 GHz are one order of magnitude less. Hence, SAW sensors capable of wireless interrogation were designed and processed on YZ-cut LiNbO3. The devices could be successfully operated in the industrial-scientific-medical (ISM) band from 2.40 to 2.4835 GHz up to 400 degrees C.
authors.affiliation: Carinthian Tech Research, Europastrasse 4/1, A-9524 Villach, Austria. rene.fachberger@ctr.at
authors.forename: René
authors.initials: R
authors.lastname: Fachberger
authors.forename: Gudrun
authors.initials: G
authors.lastname: Bruckner
authors.forename: Gernot
authors.initials: G
authors.lastname: Knoll
authors.forename: Robert
authors.initials: R
authors.lastname: Hauser
authors.forename: Jörg
authors.initials: J
authors.lastname: Biniasch
authors.forename: Leonhard
authors.initials: L
authors.lastname: Reindl