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Research on ferroelectricity and ferroelectric materials started in 1920 with the discovery by Valasek that the variation of spontaneous polarization in Rochelle salt with sign and magnitude of an applied electric field traced a complete and reproducible hysteresis loop. Activity in the field was sporadic until 1935, when Busch and co-workers announced the observation of similar behavior in potassium dihydrogen phosphate and related compounds. Progress thereafter continued at a modest level with the undertaking of some theoretical as well as further experimental studies. In 1944, von Hippel and co-workers discovered ferroelectricity in barium titanate. The technological importance of ceramic barium titanate and other perovskites led to an upsurge of interest, with many new ferroelectrics being identified in the following decade. By 1967, about 2000 papers on various aspects of ferroelectricity had been published. The bulk of this widely dispersed literature was concerned with the experimental measurement of dielectric, crystallographic, thermal, electromechanical, elastic, optical, and magnetic properties. A critical and excellently organized cpmpilation based on these data appeared in 1969 with the publica tion of Landolt-Bornstein, Volume 111/3. This superb tabulation gave instant access to the results in the literature on nearly 450 pure substances and solid solutions of ferroelectric and antiferroelectric materials. Continuing interest in ferroelectrics, spurred by the growing importance of electrooptic crystals, resulted in the publication of almost as many additional papers by the end of 1969 as had been surveyed in Landolt-Bornstein.
This volume is a joint effort of the Research Materials Information Center (RMIC) of the Solid State Division at Oak Ridge National Laboratory and the Libraries and Information Systems Center at Bell Telephone Laboratories (BTL) Murray Hill, N. J. The Research Materials Information Center has, since 1963, been answering inquiries on the avail ability, preparation, and properties of inorganic solid-state research materials. The preparation of bibliographies has been essential to this function, and the interest in ferroelectrics led to the compila tion of the journal and report literature on that subject. The 1962 book Ferroelectric Crystals, by Jona and Shirane, was taken as a cutoff point, and all papers through mid-1969 received by the Center have been included. The Libraries and Information Systems Center of BTL has, over a period of years, developed a proprie tary package of computer programs called BELDEX, which formats and generates indexes to biblio graphic material. This group therefore undertook to process RMIC's ferroelectric references by BELDEX so that both laboratories could have the benefit of an indexed basic bibliography in this important research area.
The ferroelectric material barium titanate exhibits exceptional electro-optic and dielectric properties, making it desirable for electro-optic applications, especially in thin film form. The effective nonlinear optical and dielectric properties of BaTiO3 films are determined by the ferroelectric domain structure. The ferroelectric domain structures of epitaxial BaTiO3 films on MgO (100) substrates were investigated using x-ray diffraction (XRD), scanning probe microscopy (SPM), and second harmonic generation (SHG) techniques.
Barium titanate thin films were deposited via chemical solution deposition using a hybrid-chelate chemistry directly on copper foil substrates. A process was developed to crystallize and densify the ferroelectric films at 900C by using a reductive atmosphere containing nitrogen, hydrogen, water vapor, and oxygen impurities such that film constituents were oxidized to form barium titanate and the foil substrate remained metallic. The crystallized films are polycrystalline with equiaxed morphology and average grain diameters in excess of 100 nm. The dielectric properties exhibit permittivities in excess of 1800 at room temperature and zero bias with tunabilites of greater than 90% and high field loss tangents of less than 1%. A series of samples was prepared with varying grain and crystallite sizes by dividing and processing a single film over a range of temperature from 700 to 900C. This ensures that the chemical composition and film thickness is invariant for each sample. It is shown that the grain size increases with higher process temperatures and results in a concomitant increase in permittivity and tunability. These enhancements, combined with the constant paraelectricD erroelectric phase transition temperature, indicated that a combination of film crystallinity and grain size is responsible for diminished performance. The phase transition temperature and temperature coefficient of capacitance modified by partially substituting zirconium, hafnium, and tin for titanium. The resulting films were single phase and the phase transition shifts were consistent with bulk materials. A reduction in permittivity was observed for increasing substituent level and was attributed to a reduction in grain size for both barium titanate zirconate and barium titanate hafnate. Processing conditions were chosen to stabilize Sn2+ during the firing process in an attempt to flux the system and increase grain size. The barium titanate stannate films had less reduction in grain size.