Temperature Compensated Piezoelectric Materials
Semi-annual technical no. 3, 1 Jan-31 Jun 1976
PENNSYLVANIA STATE UNIV STATE COLLEGE MATERIALS RESEARCH LAB
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In order to search for new temperature compensated materials for surface acoustic wave SAW devices with low ultrasonic attenuation and high electro-mechanical coupling, the following experimental and theoretical investigation were carried out. Extensive crystal growth investigations were carried out for Pb2KNb5O15, Li2SiO3, Ba2Si2TiO8, Ba2Ge2TiO8, and Bi2MoO5, using Czochralski or flux-pulling methods. Progress in reducing the cracking problem was made by improved temperature control during growth and subsequent cooling, and by reducing variations in the diameter of the boule during growth. Except for LiSiO3, millimeter size or larger specimen of fair to good quality have been obtained. The ferroelectric transition temperature and the lattice parameters have been studied for the system xK2O yPbO zNb2O5 in the vicinity of the stoichiometric composition corresponding to Pb2KNb5O15, and the possible implications for the composition dependence of the elastic, thermoelastic and piezoelectric constants and for attaining large electromechanical coupling factor with temperature compensated cuts are discussed. The two piezoelectric constants of AlPO4 are presently being measured by the x-ray method.