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 (F_i), the large area pyroelectric detector (F_v) and the pyroelectric point detector (F_D) were 0.517 × 10⁻¹⁰ m V⁻¹, 0.244 m² C⁻¹ and 1.437 × 10⁻⁵ Pa^1/2, 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.