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Size effect and dielectric properties of NH4H2PO4 - porous glass composites

Ciżman A., Komar J., Marciniszyn T., Poprawski R., Rysiakiewicz-Pasek E., Sieradzki A.

Materials Science Poland

2012

Vol. 30, No. 2

143--150

NH4H2PO4 nano-composite antiferroelectric materials in porous glass have been studied by means of dielectric and dilatometric investigations. Dielectric spectroscopy measurements in a wide frequency range are reported here for the first time, for both the antiferro- and paraelectric phases of ammonium dihydrogen phosphate (ADP) embedded in a porous matrix. Low frequency relaxation processes above the phase transition temperature were shown to occur. An investigation of the thermal expansion revealed a negative volume jump at the phase transition point. It was found that the phase transition temperature in ADP crystals embedded in porous glass decreased with the decrease of the mean pore size. The experimentally observed shift of the phase transition temperature is caused by a combination of size and pressure effects.

Measurement conditions of the quadratic electrooptic coefficients along the optic axis in uniaxial crystals

Izdebski M., Kucharczyk W.

Optica Applicata

2003

Vol. 33, nr 1

213-218

Following our previous discussions of measurement accuracy of electrooptic coefficients in uniaxial crystals the light wave propagation along the optic axis of ammonium dihydrogen phosphate (ADP) in a field that bisects the X and Y crystallographic axes is considered. We analyse the effect of imperfection in crystal cutting and alignment by means of computer analysis based on the Jones calculus. It is confirmed that, for relatively small inaccuracies, the values of the quadratic electrooptic coefficients can be significantly larger when measured with a static field than those measured with a sinusoidal one.