Electrical Transport in Iron Phosphate-Based Glass-(Ceramics): Insights into the Role of B2O3 and HfO2 from Model-Free Scaling Procedures.

Arijeta Bafti,Andrea Moguš-Milanković,Mustafa Yüksek,Mevlüt Karabulut,Hüseyin Ertap,Luka Pavić,Shiro Kubuki

doi:10.3390/nano12040639

Abstract

In this work, we report the effect of the addition of modifiers and network formers on the polaronic transport in iron phosphate glasses (IPG) in two systems of HfO2–B2O3–Fe2O3–P2O5, to which up to 8 mol% boron and hafnium are added. The addition of oxides significantly changes the Fe2+/Fetotal ratio, thus directly affecting the polaron number density and consequently controlling DC conductivity trends for both series studied by impedance spectroscopy. Moreover, we found that short-range polaron dynamics are also under the influence of structural changes. Therefore, we have studied them in detail using model-free scaling procedures, Summerfield and Sidebottom scaling. An attempt to construct a super-master curve revealed that in addition to change in polaron number density, also the polaron hopping lengths change, and Sidebottom scaling yields a super-master curve. The spatial extent of the localized motion of polarons is correlated with polaron number density and two distinct regions are observed. A strong increase in the spatial extent of the polaron hopping jump could be related either to the structural changes due to the addition of HfO2 and B2O3 and their effects on the formation of polarons or to an inherent property of polaron transport in IP glasses with low polaron number density.

Highlights

Introduction published maps and institutional affilThe great compositional flexibility of phosphate glasses (PG) along with properties such as low melting and transition temperatures, high thermal expansions coefficients, and ultraviolet transmission, and electrical conductivity, makes this family of glasses excellent candidates for the study of a variety of applications [1,2,3,4,5,6,7]
We use solid-state impedance spectroscopy to study in detail the electrical properties of iron phosphate glasses in which up to 8 mol% boron and hafnium oxide were added to 40Fe2 O3 −60P2 O5 base glass (G–B0Hf0)
The observed trends in long-range Direct Current (DC) conductivity show that the key parameter behind polaronic transport in these glasses is the

Summary

Introduction

The great compositional flexibility of phosphate glasses (PG) along with properties such as low melting and transition temperatures, high thermal expansions coefficients, and ultraviolet transmission, and electrical conductivity, makes this family of glasses excellent candidates for the study of a variety of applications [1,2,3,4,5,6,7]. P–O–P bridges leads to their corrosion, which is triggered by water molecules [8]. Replacing these P–O-P–bonds with more moisture-resistant bonds such as P–O–Fe or even P–O–Al with the addition of Fe2 O3 and Al2 O3 could improve the glass properties [9,10,11,12,13]. As a transition metal (TM), can occur in phosphate glasses as both, Fe2+ and Fe3+ [14,15], which strongly depends on the preparation conditions such as melting temperature, time, quenching method, composition, and affects the glass iations

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