Abstract: The structure of the barium titanate changes from cubic to tetragonal when the cooling temperature passes through the Curie temperature. This cooling process induces 90° and 180° domains in the crystal. The 90° domains, especially, are difficult to eliminate. In the present invention of this technique, the crystal is vibrated to release and dissipate the stress in the crystal, and pressed in the a-axis direction of the crystal. The vibrating contact cumulates the strength and differs from a continual press such as in the uniaxial pressure method. Consequently, only a slight force is needed to re-orient the domains, and thus eliminate the 90° domains.

Abstract: The subject invention relates to a technique employing a calibrated thermal radiometer, and the radiation characteristics of ionic crystals to measure the temperature distribution of crystals during crystal growth. When in high temperature, the ionic crystals often exhibit a transparent region having low reflectance, and low absorption in the spectrum between the short-wavelength absorption edge and the long-wavelength absorption edge. In addition, these crystals have an opaque spectral region having low reflectance and high absorption, i.e. have surface radiation of high emissivity when the spectrum is in the range between the long-wavelength absorption edge and the onset of the Reststrahlen band. The spectral emissivity of the ionic crystal may not change significantly with a variation of temperature in this opaque region.