Ozone Gas Generator Using Uniaxially Polarized LiTaO 3 Single Crystal
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Ozone Gas Generator Using Uniaxially Polarized LiTaO3 Single Crystal Yoshikazu Nakanishi1, Junko Ide2, Jun Kondo2, Shinji Fukao1, Katsumi Handa2, Tatsunori Tochio3, Yoshiaki Ito2, Akikazu Tanaka4, and Shinzo Yoshikado1 1 Department of Electronics, Doshisha University, 1-3, Tatara-Miyakodani, Kyotanabe, Kyoto, 610-0321, Japan 2 Institute for Chemical Research, Kyoto University, Gokasyo, Uji, Kyoto, 611-0011, Japan 3 Keihanna Interaction Plaza Incorporated, 1-7, Hikaridai, Seika-cyo, Soraku-gun, Kyoto, 619-0237, Japan 4 Sumitomo Metal Mining Co. Ltd., 5-11-3, Shinbashi, Minato-ku, Tokyo, 105-8716, Japan ABSTRACT The very simple and easy generating method of ozone gas (O3 gas) that is very different from the conventional methods is provided. O3 gas could be generated in the air using a high electrical field generated around a ferroelectric (pyroelectric) crystal (LiTaO3) by thermally exciting. The generation of O3 gas depends on the differences of the upper limit temperature of the crystal, temperature gradient, materials faced to the rear side of the crystal, and electric positive or negative surface of the crystal. The results suggested that the induced electric field by the polarization of the crystal is important to generate O3 gas. INTRODUCTION LiTaO3 or LiNbO3 is well known as a ferroelectric crystal and is used in such devices as modulators, filters, and polarization converters. At temperatures below the Curie temperature Tc (~900 K) of LiTaO3, the centers of positive and negative charges in a LiTaO3 crystal are separated spatially and the crystal is polarized. Structural investigations of LiNbO3 show that deviations from stoichiometry are a major influence on physical properties [1-3]. Brownridge [4] have reported X-ray emission during temperature changes of pyroelectric materials like LiTaO3 in a vacuum. Subsequently, his group and ours have independently investigated X-ray generation by ferroelectric crystals: in a vacuum of approximately 3 to 6 Pa or a low gas pressure atmosphere, with periodically changing the temperature of this crystal, charged particles including electrons are generated on the surface of the crystal because the particles that cannot follow the offset of the charge on the surface collide with a target or a pyroelectric crystal, and thus, X-rays generate [5-9]. Near recently, we discovered that the air can be efficiently ozonized simply by thermally exciting LiTaO3 or LiNbO3 crystal, and therefore, ozone gas (O3 gas) can be easily generated with a high concentration, without requiring any special equipment, such as a vacuum apparatus, a high voltage power supply, and without using an X-ray target, such as of a heavy metal. Industrially, O3 gas is widely used to, for example, wash fresh fruits and vegetables to kill yeast, mold and bacteria, and hospital operating rooms where air needs to be sterile etc.. Therefore, near future the device and/or treatment have to go through rigorous trials. In the present study, the generation of O3 gas was investigated using sample crystals of
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