Effect of xylenol orange dye on morphological, optical, piezo-/di-electric and mechanical properties of potassium hydrogen phthalate single crystals

Abstract

Pure and xylenol orange (XO; C13H32N2O13S;0.1 mol%) dye doped potassium hydrogen phthalate (KAP; C8H5KO4) crystal were grown by solution technique. Only {111‾} & {110} growth sectors of KAP crystal got selectively stained by the XO dye molecules with {010} being the largest visible (morphologically important) plane. Powder XRD pattern reveals that XO dyeing did not resulted in any extra Bragg peaks and hence, didn't changed the basic structure of KAP crystal (PCa21). HRXRD and etch pit density studies were performed to investigate the effect of XO dye staining on the crystallinity of KAP crystal.The Piezoelectric charge coefficient increased (1.42–1.62 pC/N), optical transparency increased (30%–50%), mechanical strength improved (10.2–11 kg/mm2 @ 20 g), dielectric constant enhanced (ε' ~40 to 44 @ 1 kHz) and dielectric loss decreased (~0.09 to ~0.02) due to XO dye doping. Comparative optical, mechanical, piezoelectric and dielectric investigations add to the scientific insights of KAP crystals and suggest XO-dyed KAP crystal as a better alternative than pure KAP crystal for opto-electronic devices applications.