Interpretation of experimental findings on the structure of glass in the CaO–MoO3–P2O5 system using a thermodynamic model including oxidation–reduction equilibria

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F60461373%3A22310%2F24%3A43931226" target="_blank" >RIV/60461373:22310/24:43931226 - isvavai.cz</a>

Result on the web

<a href="https://link.springer.com/article/10.1007/s10973-023-12511-8" target="_blank" >https://link.springer.com/article/10.1007/s10973-023-12511-8</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1007/s10973-023-12511-8" target="_blank" >10.1007/s10973-023-12511-8</a>

Result language

angličtina

Original language name

Interpretation of experimental findings on the structure of glass in the CaO–MoO3–P2O5 system using a thermodynamic model including oxidation–reduction equilibria

Original language description

This work extends the thermodynamic model of associated solutions used in the past to describe the structure and properties of glasses to the area of complex multicomponent glasses with polyvalent elements, where it has not been applied until now either due to the absence of Gibbs energies of formation of the necessary compounds or due to oxidation–reduction equilibrium in the presence of a gas phase containing oxygen. While the fitting of unknown Gibbs energies based on experimental data has already been applied to some extent in our previous work, the implementation of redox is, to the best of our knowledge, new. Four concentration series were taken from the published data from the glass-forming ternary system CaO–MoO3−P2O5: A) xMoO3−(0.5–0.75x)CaO−(0.5–0.25x)P2O5; B) xMoO3−(0.5–0.875x)CaO−(0.5–0.125x)P2O5; C) xMoO3−(0.5−x)CaO−0.5P2O5; M) xMoO3−(1−x)P2O, for which the distributions of Qn units were also published (Q denotes the PO4 tetrahedral unit with n bridging oxygens) by the 31P MAS NMR method and the Mo[V]/ΣMo fraction by the ESR method [Černošek et al. (J Solid State Chem 303:122522, 2021); Holubová et al., (J Non-Cryst Solids 607:122222, 2023)]. The following compounds were considered in the TD model: P2O5, CaO, Mo[VI]O3, Ca(PO3)2, Ca2P2O7, (Mo[VI]O2)(PO3)2, (Mo[VI]O2)2(P2O7), (Mo[VI]O2)3(PO4)2, (Mo[V]O)2(PO3)2(P2O7), (Mo[V]O)PO4. All except the hypothetical compound (Mo[VI]O2)3(PO4)2 exist, and their structure is known. Binary phosphate compounds with molybdenum lack Gibbs energies of formation. Therefore, one of the series, namely A, was used to determine these energies by nonlinear regression with the help of a genetic algorithm, without/with redox, and then the distribution of Qn units and the fraction of Mo[V]/ΣMo was predicted for the remaining series. It was found that the distribution of Qn units can be described by the TD model with redox only. During the reduction of molybdenum, the distribution of Qn unit’s changes, and thus also the connectivity of the phosphate network, for example, according to the reactions: (MoO2)2(P2O7)—&gt; 2(MoO)PO4 + 1/2O2, in which Q1—&gt; Q0 and 2(MoO2)(PO3)2—&gt; (MoO)2(PO3)2(P2O7) + 1/2O2 in which Q2—&gt; Q1. Despite the fact that the TD model with redox gives excellent agreement in the case of the Qn distribution, the agreement with the ESR measurements of the Mo[V]/ΣMo ratio is not good. The TD model predicts significantly more pentavalent molybdenum in the glass. © The Author(s) 2023.

Czech name

—

Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

20504 - Ceramics

Project

<a href="/en/project/LTT20001" target="_blank" >LTT20001: Surfaces of silicate glass; characterization, structure, and modification. Cooperation with Centre of excellence FunGlass.</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2024

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY

ISSN

1388-6150

e-ISSN

1588-2926

Volume of the periodical

149

Issue of the periodical within the volume

20

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

14

Pages from-to

11429-11442

UT code for WoS article

001068809400001

EID of the result in the Scopus database

2-s2.0-85171475652