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A new catalytic system containing ferric chloride, activated carbon, and hydrazine has been proposed for the reductive cyclization of -dialkylamino-2-nitrostyrenes to give the corresponding indoles (Leimgruber-Batcho synthesis). Various substituted indoles may be obtained in high yield under these conditions.

Absfruct -The thermodynamical consideration of the changes in tensor components of &electric susceptibdities of ferroelectrics singledomain crystals under the influence of one-dimensional mechanical stress'is done. It has been shown that the regstration of such changes together with occurring non-180' reorientations of domains allows us to gve an adequate description of the microwave dielectric permitthrity behaviour of ferroelectric ceramics. Quantitative evaluation of 90" reorientations share in BaTi03 ceramics with crystallites of different sizes have been done. Experimental data for BaTiQ and PZT ceramics are presented. TNTRODUCTIONFerroelectrics (FE) properties control by means of external influences opens great possibilities for the practical use of FE. However. the mechanisms of the external action influence on FE physical properties have not been sufficiently studied yet. In particular, big difficulties arise from the interpretation of the changes of &electric permittivity E* of FE ceramics under the influence of electric field and/or mechanical stresses o. The present paper is aimed at proposing a simple theoretical description of the E* (a) dependence and at comparing its results with the available experimental data. THEORY AND EXPERIMENTWe shall consider a simplified model of unpolarized tetragonal FE ceramics presented here as a set of singledomain crystallites, their polar axes are oriented with the same probability along three mutually perpen&cular axes of the general Decart's coordinate system X Y Z . Under the influence of the onedmensional mechanical stresses applied along Z axis, dielectric permittivity of the considered FE ceramics sample will be changed due to the following reasons: a) the changes of tensor components and E $~ of ctystallite dielectric permittivity; 0-7803-4959-8/98/$10.00 0 1998 IEEE. b) 90' polar axes reorientations of the part of crystallites to the dxection. parallel to Z axis (cT~>O stretching stress) or to the direction perpendicular to Z axis ( q < O compressing stress). Below we will consider both above-mentioned effects. includes three successive steps: Due to statistical nature of ceramics E* its calculating -the calculation of E and E :3 dependences; -averaging calculated and E!& values;-talung into account domain switchings for all used of o values. Changes of and E $~ components of lowfrequency dielectric permittivity E of a stress-free singledomain crystal can be calculated Bithin the framework of the thermodynamical theory. by using a standard expansion of the function of free energy F(P.0) to the power series by the components of the polarization P and mechanical stresses 0 [l]. This procedure gives the following expressions for the low frequency dielectric susceptibilities xyl and xi3 and spontaneous polarization Ps: F(P, CS) = Fo(T) + a(P: + Py' + P : ) + % ( P: + Py" + + P; )+ p2(pX' p; + Py'Pz' + P: P: ) + "(Px" + Py" + P: )+ 3 533

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