Enhancement of the photoluminescence modulation ratio in highly transparent KNN-based ceramics for optical information storage

Abstract

Transparent photochromic materials have attracted extensive attention in applications of optical information storage and optical switches, in which both high transparency and large switching contrast are required. In this work, K_0.5Na_0.5NbO₃–xPr (x = 1.0, 2.0, 2.5, 3.0) ceramics were prepared by pressure-less sintering. When x ≥ 2.0, high transmittances (T) were achieved due to the small grain size and the highly symmetrical phase structure. Optimal transmittances of ∼72.9% at 900 nm and ∼73.9% at 2500 nm were obtained in the K_0.5Na_0.5NbO₃–3Pr ceramic. The transmittance and photoluminescence intensity can be obviously modulated by photochromism and have been found to be closely related to the Pr doping amount. A high modulation ratio of luminescence intensity (ΔR_L) of ∼ 81% was obtained by illumination in the transparent K_0.5Na_0.5NbO₃–3Pr ceramic (with T ∼ 72.9% at 900 nm), while a modulation ratio of transmittance (ΔR_T) of 29% was achieved in the transparent K_0.5Na_0.5NbO₃–2Pr ceramic (with T ∼ 63.3% at 900 nm). The transmittance and photoluminescence intensity recover to the original state by heating and both the ΔR_T and ΔR_L show good stability when the ceramics are alternately modulated by illumination and thermal stimulation. The combination of high transparency and large switching contrast makes Pr-doped K_0.5Na_0.5NbO₃ ceramics promising for optical information storage and optical switch applications.