Evidence of phase transition in Nd³⁺doped phosphate glass determined by thermal lens spectrometry

Abstract

Thermal lens spectroscopy (TLS), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) techniques were applied to the thermo-optical property analysis of a new phosphate glass matrix PANK with nominal composition 40P2O5·20Al2O3·35Na2O·5K2O (mol%), doped with different Nd(3+) compositions. This glass system, synthesized by the fusion protocol, presents high transparency from UV to the near infrared, excellent thermo-optical properties at room temperature and high fluorescence quantum efficiency. Thermal lens phase shift parameters, thermal diffusivity and the DSC signal present pronounced changes at about 61 °C for the PANK glass system. This anomalous behavior was associated with a phase transition in the nanostructured glass materials. The FTIR signal confirms the presence of isolated PO4 tetrahedron groups connected to different cations in PANK glass. As a main result, our experimental data suggest that these tetrahedron groups present a structural phase transition, paraelectric-ferroelectric phase transition, similar to that in potassium dihydrogen phosphate, KH2PO4, nanocrystals and which TLS technique can be used as a sensitive method to investigate changes in the structural level of nanostructured materials.

Importance of Molecular Structure on the Thermophoresis of Binary Mixtures

“…The amount of heat deposited in the system depends on the amount of radiationless relaxation. Presently, TL spectroscopy is a well-known, highly sensitive, nondestructive, popular analytical technique − for the thermal, optical, and chemical analysis of solids, liquids, and gases. − …”

Estudo do comportamento atérmico no sistema vítreo fosfato PANK em função da razão K2O/Al2O3

“…A partir desses resultados, foi ampliado o estudo nessa matriz buscando avaliar os parâmetros termo-óticos em função da temperatura [37,64]. Os resultados mostraram que esse vidro apresenta uma reorganização estrutural reversível próximo da temperatura ambiente, devido à uma possível expansão térmica negativa, e que está em acordo com os resultados de difusividade térmica em função da temperatura obtido via técnica de LT e medida de calorimetria diferencial de varredura (DSC).…”

“…Para explicar este efeito, Andrade et. al [64] sugeriram que este material tem uma expansão térmica negativa acima da temperatura…”