Pyroelectric and second harmonic responses from LiTaO3 nanocrystallites evolved in a Li2O–B2O3–Ta2O5 glass system†
Abstract
Dendritic growth of trigonal and square bipyramidal structures of LiTaO3 nanocrystallites, of 19–30 nm size, was observed when 1.5Li2O–2B2O3–0.5Ta2O5 glasses were subjected to controlled heat treatment between 530 °C and 560 °C/3 h. X-ray diffraction and Raman spectral studies carried out on the heat-treated samples confirmed the formation of a LiTaO3 phase along with a minor phase of ferroelectric Li2B4O7. The sample that was heat-treated at 550 °C/3 h was found to possess ~26 nm sized crystallites which exhibited a pyroelectric coefficient as high as 15 nC cm−2 K−1 which is in the same range (23 nC cm−2 K−1) as that of single crystalline LiTaO3 at room temperature. The corresponding figures of merit that were calculated for the fast pulse detector (Fi), the large area pyroelectric detector (Fv) and the pyroelectric point detector (FD) were 0.517 × 10−10 m V−1, 0.244 m2 C−1 and 1.437 × 10−5 Pa1/2, respectively. Glass nanocrystal composites comprising ~30 nm sized crystallites exhibited broad Maker fringes and the second harmonic intensity emanated from these was 0.5 times that of KDP single crystals.