Dielectric, pyroelectric and ferroelectric properties of lead-doped Sn₂P₂S₆ crystals

ABSTRACT

The dielectric, pyroelectric and ferroelectric properties of (Pb_ySn_1−y)₂P₂S₆ (y = 0.1, 0.2 and 0.3) single crystals were analysed in the vicinity of phase transition. The measurements were done covering a wide range of frequency (20 Hz to 1 MHz) and temperature (30350 K) range. Structural phase transition temperature decreases with increased lead concentration and evokes the broadening of the dielectric anomaly. The features of this phase transition are discussed and related to stereoactivity of Sn²⁺ ions and fluctuations of the concentration of Pb²⁺ ions. Pyroelectric measurements were performed from 190 K to 325 K during the heating cycle. These investigations showed that an increase of lead concentration does not affect the maximum value of pyroelectric coefficient, and the maximum values of pyroelectric coefficients γ_max which (in the vicinity of the phase transition temperature) are nearly equal to 250 nC cm⁻² K⁻¹ for all the compositions. The temperature evolution of polarization hysteresis loops proved crystals being ferroelectrics.

KEYWORDS:

• Dielectric spectroscopy
• pyroelectric properties
• ferroelectrics
• Sn₂P₂S₆ crystal