# ZBLAN glass 3D printing: the first steps

Elodie Galdo, Solenn Cozic, Leo Szymczyk, François Cheviré, Ronan Lebullenger, Antoine Gautier, Laurent Calvez, Samuel Poulain, Marcel Poulain, Johann Troles

► To cite this version:

Elodie Galdo, Solenn Cozic, Leo Szymczyk, François Cheviré, Ronan Lebullenger, et al.. ZBLAN glass 3D printing: the first steps. Optical Materials Express, 2025, 15 (6), pp.1189. 10.1364/OME.562288 . hal-05076608

HAL Id: hal-05076608

https://hal.science/hal-05076608v1

Submitted on 3 Jun 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# ZBLAN glass 3D printing: the first steps

ELODIE GALDO,<fnref n="1" />,<fnref n="2" /> SOLENN COZIC,<fnref n="2" /> ID LEO SZYMCZYK,<fnref n="1" /> FRANÇOIS CHEVIRE,<fnref n="1" /> ID RONAN LEBULLENGER,<fnref n="1" /> ANTOINE GAUTIER,<fnref n="1" /> LAURENT CALVEZ,<fnref n="1" /> SAMUEL POULAIN,<fnref n="2" /> MARCEL POULAIN,<fnref n="1" />,<fnref n="2" /> AND JOHANN TROLES<fnref n="1" />,*

**Abstract:** Fluoride glasses, particularly ZBLAN, exhibit exceptional optical properties, including low dispersion, high transmittance, and broad transparency in the mid-infrared spectrum. These characteristics make them highly attractive for applications such as mid-IR lasers, spectroscopy, and optical fiber technologies. In this study, we explore the feasibility of 3D printing ZBLAN glass using a fused filament fabrication (FFF) approach. The synthesis of high-purity ZBLAN glass rods was carried out, followed by an in-depth analysis of their thermal properties to determine optimal processing conditions. By adjusting extrusion temperatures and printing parameters, we successfully demonstrated the deposition of fluoride glass layers. The glassy state of the printed ZBLAN was verified, and a transmission of over 50% was achieved with the 3D-printed glass. This work represents a significant step toward additive manufacturing of advanced optical components, paving the way for new applications in infrared optics, fiber preforms, and customized glass microstructures.

Published by Optica Publishing Group under the terms of the [Creative Commons Attribution 4.0 License](https://creativecommons.org/licenses/by/4.0/). Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

## 1. Introduction

Fluoride glasses, is a class of amorphous materials characterized by their high transparency in the infrared region. The exceptional optical properties of fluoride glasses, including low dispersion, high transmittance, and broad transparency in the mid-infrared spectrum, make them highly attractive for a wide range of technological applications such as mid-IR laser, and mid-IR sensing [1-4]. Indeed, the fluoride glasses exhibit transmission until 4-5 µm where traditional silica fibers encounter limitations for longer wavelength than 2.5 µm for meters long fibers [5,6]. Their transparency in the mid-infrared region makes them ideal candidates for infrared spectroscopy [7], with potential applications in medical diagnostics [8], environmental monitoring [3], mid infrared interferometry for astronomy [9].

In addition, thanks to their high capability to host rare earth ions, fluoride glasses are also of great interest for the development of lasers not only in the mid-IR. Indeed, there is also a great interest for numerous visible wavelength lasers [10,11].

The manufacturing of 3D printed glass objects has progressed over the past decade, initially done with silicates [12], other glassy systems have been studied such as phosphate glasses [13], lead-borosilicate glasses [14] and chalcogenide glasses [15,16]. All these studies used the filamentation method based on the extrusion of a glass filament through a heated nozzle.

However, other processes have also been investigated to “3D print” glasses such as laser sintering of glass powders [17], laser heating of glass filaments [18], ink deposition [19,20], or photopolymerization of photocurable resins containing glass particles (i.e. stereolithography) [21] both requiring thermal post-treatments for debinding the resins [21].

<footnote n="1">¹Univ Rennes, CNRS, ISCR-UMR 6226, F-35000 Rennes, France</footnote>

<footnote n="2">²Le Verre Fluoré, Rue Gabriel Voisin, Campus Kerlann, 35170 Bruz, France</footnote>

<footnote>*johann.troles@univ-rennes.fr</footnote>
The advantage of additive manufacturing is the ability to save raw materials and create complex optical shapes. This makes it possible to produce lenses, microlenses, lens arrays [18,22], glass beads [16] and fiber preforms [14,23,24] as examples.

In this study, the fused filament fabrication of ZBLAN glass was investigated. ZBLAN glass rods and canes were fabricated, and their thermal properties were analyzed before being used as raw materials for 3D printing. After determining the suitable conditions for filament extrusion of the glass and for glass printing, the physical and optical properties of the printed ZBLAN glass were examined and compared to those of the pristine ZBLAN glass.

## 2. ZBLAN glass

### 2.1. ZBLAN synthesis for feeding the 3D printer

In this work, the common ZBLAN glass with a composition of 53% ZrF₄, 20% BaF₂, 4% LaF₃, 3% AlF₃, and 20% NaF has been prepared. Fluoride glasses are synthesized through a meticulous process that emphasizes purity and controlled conditions to prevent contamination and crystallization. High-purity fluoride compounds, such as zirconium fluoride (ZrF₄), barium fluoride (BaF₂), lanthanum fluoride (LaF₃), aluminum fluoride (AlF₃), and sodium fluoride (NaF), are accurately weighed and mixed. The mixed batch is placed in a platinum crucible to avoid contamination and then heated up to temperatures above 800°C in a dry atmosphere and then fined for 1 hour. This high-temperature melting ensures that the materials form a homogeneous molten mixture. The refined molten glass is then rapidly cooled, or quenched, by casting it into a brass mold that was preheated below the glass transition temperature (Tg) of the ZBLAN. Such rapid cooling prevents the formation of crystals, resulting in an amorphous glass structure. Finally, the glass is annealed at its Tg for 1 hour and then gradually cooled. This annealing process relieves internal stresses induced during quenching, enhancing the glass's mechanical stability.

The drawing of a ZBLAN glass rod from an initial diameter of 18 mm (Fig. 1(a)) to a finer cane of 2.7 mm (Fig. 1(b)) is carried out using a dedicated fluoride glass fiber-drawing tower. This process requires precise thermal control to maintain the amorphous structure of the glass while avoiding crystallization. The 18 mm ZBLAN glass rod is carefully cleaned to remove any surface contamination that could lead to defects during the drawing process. It is then mounted vertically in the fiber-drawing tower, held by a specialized chuck or holder. The glass rod is gradually lowered into a high-purity, temperature-controlled furnace, specifically designed for fluoride glasses. The furnace operates in a dry neutral atmosphere to prevent moisture absorption and oxidation, which could degrade the optical quality of the glass. Once the ZBLAN rod reaches its softening temperature (typically between 300°C and 400°C), it begins to deform by gravity under its own weight. At this stage, a mechanical pulling system is engaged to precisely control the elongation of the softened glass. The pulling speed and furnace temperature are carefully adjusted to ensure a uniform reduction in diameter from 18 mm to 2.7 mm. (Fig. 1)

### 2.2. ZBLAN thermal properties

Additive manufacturing by filamentation requires a thorough understanding of the thermal properties of the materials used. Before the first extrusion tests and thus 3D printing, a DSC analysis was performed on a sample of a ZBLAN cane that will be used by the printer. Figure 2(a) presents the thermal analysis of a piece of ZBLAN rod (solid black line curve). The glass transition temperature and the crystallization onset temperature were measured at 258°C and at 349°C, respectively (Measurement carried out with a heating rate of 10 °C/min.). These measurements are consistent with other values found in the scientific literature [25,26]. This small difference between the glass transition temperature and the onset of crystallization (ΔT = 91°C)
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** (a) ZBLAN rod (Ø 18 mm), (b) ZBLAN canes used for feeding the 3D printer (Ø = 2.7 mm).</figcaption></figure>

will represent one of the challenges to overcome in the manufacturing of fluoride glass parts by
additive manufacturing.

<figure><img src="image_4.png" /><figcaption>**Fig. 2.** Initial ZBLAN thermal properties, (a) DSC analysis, (b) Viscosity versus temperature.</figcaption></figure>

The temperature-dependent viscous behavior of ZBLAN rods was also investigated using a THETA viscometer. The viscosity curve as a function of temperature is shown in Fig. 2(b). The measurement method (i.e. compression of a glass cylinder recorded by a linear variable differential transformer) does not allow to measure viscosities below 10⁵ Pa.s. However, the viscosity of the ZBLAN glass has been measured from 250 °C to 315° C at 10¹² Pa.s to 10⁵ Pa.s, respectively. These values of viscosity are in accordance with measurements reported in [6,27]. Usually, for filament-based printing, the required viscosities are typically in the range of 10¹⁻¹⁰ Pa.s [16,28]. In the present case, by extrapolating the curve in Fig. 2(b), the extrusion head of our printer must reach a minimum temperature of 330°C to achieve a suitable viscosity of the ZBLAN glass. However, it will be also necessary to remain below the crystallization temperature of 350°C.

**3. ZBLAN 3D printing**

The 3D-printing set-up is based on a customized commercial cartesian Arduino-based RepRap-
style 3D printer upgraded for soft glasses and running Marlin firmware. Especially, the feeding
mechanism is customized to handle suitably brittle materials as used in [16]. This mechanism is
supplied with 200-250 mm long glass rods of 2.7 mm diameter that are produced by the fiber
drawing method. An extruder drives the raw material filament to a nozzle heated well above Tg. The printer head moves along the X and Z axes while depositing the ZBLAN glass as 100 µm-thick layers and the bed plate moves along the Y axis. The temperature of the copper-based hot end was investigated from 320 to 350 °C. The size of the nozzle (brass nozzle), and consequently, the width of the printed filament was about 800 µm. The ZBLAN glass was deposited on an ZBLAN glass print bed heated around slightly above Tg (i.e. slightly above Tg) in order to ensure a good adhesion of the first printed layers. Indeed, first 3D printings attempts have been done on different bed supports (window glass, iron or aluminium beds) however, the adhesion of the first extruded lines/layers was not sufficient and did not permit to print bulk glasses. For this reason, a ZBLAN support has been molded in order to be used as a printing bed. Only the printing of ZBLAN on ZBLAN permits the realization of a bulk printed disk (Fig. 3(b)). For an optimum control of the extrusion and of the nozzle displacement during printing, a simple G-code input file was written using concentric circular motion commands. The Fig. 3(a) illustrates the displacement pattern of the printing head.

<figure><img src="image_5.png" /><figcaption>**Fig. 3.** Printed ZBLAN disk (a) G-Code patter lines used for the printing, (b) ZBLAN disk obtained by fused filamentation fabrication.</figcaption></figure>

The investigation of the optimum extrusion temperature was one of the key points of the study in order to reach a suitable viscosity without crystallization. After several tests, an operating temperature of 342°C enabled effective extrusion without crystallization. It then became possible to print a small disk with a diameter of 8 mm and a thickness of 1.2 mm (12 layers of 100 µm), as illustrated in Fig. 3(b).

**4. Results and discussion**

During the various tests, the maximum printing duration before extrusion stopped was 10-20 minutes. For this reason, only small sample could be printed. Crystallization was observed at the extrusion nozzle outlet. However, no crystallization was detected inside the nozzle itself. The crystallization occurred just at the exit of the print head. Indeed, after printing, the brass nozzle was cut longitudinally in half to observe its interior, and no signs of crystallization were observed under the optical microscope, except at the nozzle outlet. One can note, that the configuration of the printer used did not allow for a perfectly dry atmosphere at the nozzle outlet. The moisture probe indicated an H₂O level between 200 and 400 ppm. Such relatively high humidity rate inside the chamber may explain the crystallization of ZBLAN at the nozzle exit. Indeed, the ZBLAN could be sensitive to moisture more particularly at temperature higher than its Tg.

Although printing often stops after about twenty minutes due to glass crystallization at the nozzle outlet, no evidence of crystals presence has been observed through X-ray diffraction (XRD) on printed ZBLAN parts (Fig. 4(a)). The XRD patterns do not show any significant diffraction peaks, even though data acquisition between 2θ = 10° and 60° was recorded over a
12-hour period. However, differential scanning calorimetry (DSC) analysis of the printed glass shows that the crystallization temperature decreased from 349°C for the initial glass to 321°C for the printed glass (Fig. 4(b), Tab. 1). The glass transition temperature, on the other hand, remained unchanged between the initial and printed glass.

<figure><img src="image_6.png" /><figcaption>**Fig. 4.** Physical and optical properties of the Printed ZBLAN compared to the initial Glass. (a) XRD measurements, (b) Differential Scanning Calorimetry measurements, (c) SEM image and (d) Optical transmission.</figcaption></figure>

<table><caption>**Table 1.** Physical properties of as-prepared and printed ZBLAN</caption><thead><tr><th></th><th>Tg onset<sup>a</sup><br>(°C) (± 2 °C)</th><th>Tx onset<sup>a</sup><br>(°C) (± 2 °C)</th><th>Density<sup>a</sup><br>(g/cm, ± 2%)</th><th>Maximum of<br>transmission (%)</th></tr></thead><tbody><tr><th>Initial</th><td>258</td><td>349</td><td>4.52</td><td>92</td></tr><tr><th>Printed glass</th><td>256</td><td>321</td><td>4.29</td><td>55</td></tr></tbody></table>

The decrease in the crystallization temperature of the printed glass compared to the original glass may indicate the presence of nuclei and/or nanocrystals generated during printing. However, their quantity or size is not sufficient to be detected by X-ray diffraction.

The most significant difference observed between the initial glass and the printed glass is the optical quality and maximum transmission of the glass. Indeed, the maximum transmission of the printed glass is 55% (@ 5.4 µm), even on a polished sample after printing, whereas the initial ZBLAN glass transmits up to 92% (4% Fresnel losses per face) at the same wavelength (Fig. 4(c)).

The XRD and DSC analyses showed that the printed glass had very slightly crystallized. The presence of crystals alone cannot therefore explain this transmission degradation. A cross-sectional image (Fig. 4(d)) of the printed glass revealed the presence of pores, likely at the

<footnote><sup>a</sup>Heating rate 10°/min;</footnote>

<footnote><sup>b</sup>Measured using Archimedes double weighing method in air and then in ethanol.</footnote>
interfaces between the different printed layers. The presence of these pores or bubbles, ranging in size from 1 µm to 30 µm, leads to strong light scattering and thus explains the reduction in the transmission of the printed glass. The presence of these cavities also explains the decrease in the density of the printed glass compared to the initial glass (Table 1).

Such defects are commonly observed in 3D printing [14,16,22]. The quantity of these printing defects could be significantly reduced in future studies by optimizing printing parameters such as speed, nozzle size, extrusion head temperature, and the temperature of the print bed and chamber [16]. Particularly in the case of ZBLAN glasses, implementing printing in an enclosure with a neutral atmosphere (free of humidity and oxygen) would be essential.

**5. Conclusion**

In this study, we have presented the first demonstration of 3D printing of fluoride glass using a fused filament fabrication approach. Beginning with the synthesis of high-purity fluoride glass rods, we established a process that enables their use as feedstock for additive manufacturing. Through systematic investigations, we identified suitable printing conditions that allow the extrusion and deposition of fluoride glass filaments while preserving its physical and optical properties.

Our results demonstrate that fluoride glass can be successfully processed using 3D printing while maintaining its glassy state and achieving 55% transmission in the mid-infrared range, paving the way for new fabrication methods in advanced optical applications. This breakthrough opens possibilities for the rapid prototyping and customization of fluoride glass components, which could benefit fields such as infrared optics and fiber optics. Future work will focus on optimizing the printing parameters and exploring the integration of this technique into practical optical systems.

**Funding.** Agence Nationale de la Recherche (ANR-21-ESRE-0007 ADD4P); Association Nationale de la Recherche et de la Technologie; Région Bretagne; Ministère de l'Enseignement supérieur, de la Recherche et de l'Innovation.

**Acknowledgments.** This work was funded in part by the French ANRT through the CIFRE PhD program, the European Union through the European Regional Development Fund (ERDF), the Ministry of Higher Education and Research, the french region of Brittany, and by a grant overseen by the French National Research Agency (ANR) as part of the "France 2030" Program, the ANR-21-ESRE-0007 ADD4P project.

**Disclosures.** The authors declare no conflicts of interest.

**Data availability.** Data underlying the results presented in this paper are not publicly available but may be obtained from the authors upon reasonable request.

**References**

1. N. B. Chichkov, A. Yadav, F. Joulain, et al., "Amplification of GaSb-Based Diode Lasers in an Erbium-Doped Fluoride Fibre Amplifier," *IEEE Photonics J.* **15**(1), 1–7 (2023).

2. S. Venck, F. St-Hilaire, L. Brilland, et al., "2-10 μm Mid-Infrared Fiber-Based Supercontinuum Laser Source: Experiment and Simulation," *Laser Photonics Rev.* **14**(6), 2000011 (2020).

3. P. Bernard, B. Labranche, and Y.-M. Cyr, "Use of fluoride fibers for NDIR monitoring of hydrogen fluoride in aluminum smelters," in *Infrared Glass Optical Fibers and Their Applications*, (SPIE, 1998), 23–30.

4. V. Fortin, M. Bernier, S. T. Bah, et al., "30 W fluoride glass all-fiber laser at 2.94 µm," *Opt. Lett.* **40**(12), 2882–2885 (2015).

5. J. Lucas, J. Troles, X. H. Zhang, et al., "Glasses to see beyond visible," *C. R. Chim.* **21**(10), 916–922 (2018).

6. M. Poulain, "Heavy metal fluoride glasses: A tutorial review," *APL Photonics* **9**(9), 091103 (2024).

7. J. P. Laviolette, G. S. Patience, and J. Chaouki, "Simultaneous quantitative measurement of gaseous species composition and solids volume fraction in a gas/solid flow," *AICHE J.* **56**(11), 2850–2859 (2010).

8. T. N. Murray, H. Maredia, and P. M. Friedman, "Histological analysis of laser-enabled tissue coring with a novel 2910 nm erbium-doped fluoride glass fiber laser," *Lasers Surg. Med.* **56**(5), 462–465 (2024).

9. K. Perraut, L. Jocou, J. P. Berger, et al., "Single-mode waveguides for GRAVITY," *Astron. Astrophys.* **614**, A70 (2018).

10. Y. X. Zhao and S. Fleming, "Theory of Pr3+-doped fluoride fiber upconversion lasers," *IEEE J. Quantum Electron.* **33**(6), 905–915 (1997).

11. E. Kifle, F. Starecki, P. Loiko, et al., "Watt-level visible laser in double-clad Pr3+-doped fluoride fiber pumped by a GaN diode," *Opt. Lett.* **46**(1), 74–77 (2021).
12. J. Klein, M. Stern, G. Franchin, et al., "Additive Manufacturing of Optically Transparent Glass," 3D Printing and Additive Manufacturing 2(3), 92–105 (2015).

13. R. M. Zaki, C. Strutynski, S. Kaser, et al., "Direct 3D-printing of phosphate glass by fused deposition modeling," Mater. Des. **194**, 108957 (2020).

14. P. Gołębiewski, P. Wienclaw, J. Cimek, et al., "3D soft glass printing of preforms for microstructured optical fibers," Addit. Manuf. **79**, 103899 (2024).

15. E. Baudet, Y. Ledemi, P. Larochelle, et al., "3D-printing of arsenic sulfide chalcogenide glasses," Opt. Mater. Express **9**(5), 2307–2317 (2019).

16. J. Carcreff, F. Chevire, R. Lebullenger, et al., "Investigation on Chalcogenide Glass Additive Manufacturing for Shaping Mid-infrared Optical Components and Microstructured Optical Fibers," Crystals **11**(3), 228 (2021).

17. M. Fateri and A. Gebhardt, "Selective Laser Melting of Soda-Lime Glass Powder," Int. J. Appl. Ceram. Technol. **12**(1), 53–61 (2015).

18. C. Liu, T. Oriekhov, C. Lee, et al., "Rapid Fabrication of Silica Microlens Arrays via Glass 3D Printing," 3D Print Addit Manuf **11**(2), 460–466 (2024).

19. D. T. Nguyen, C. Meyers, T. D. Yee, et al., "3D-Printed Transparent Glass," Adv. Mater. **29**(26), 1701181 (2017).

20. B. Nan, P. Gołębiewski, R. Buczyński, et al., "Direct Ink Writing Glass: A Preliminary Step for Optical Application," Materials **13**(7), 1636 (2020).

21. F. Kotz, K. Arnold, W. Bauer, et al., "Three-dimensional printing of transparent fused silica glass," Nature **544**(7650), 337–339 (2017).

22. G. Berglund, A. Wisniowiecki, J. Gawedzinski, et al., "Additive manufacturing for the development of optical/photonic systems and components," Optica **9**(6), 623–638 (2022).

23. J. Carcreff, F. Cheviré, E. Galdo, et al., "Mid-infrared hollow core fiber drawn from a 3D printed chalcogenide glass preform," Opt. Mater. Express **11**(1), 198–209 (2021).

24. Y. Chu, X. Fu, Y. Luo, et al., "Silica optical fiber drawn from 3D printed preforms," Opt. Lett. **44**(21), 5358–5361 (2019).

25. L. Battezzati and M. Baricco, "An experimental study of thermodynamic properties in a ZBLAN glass-forming system," Mater. Sci. Eng., **A 133**, 584–587 (1991).

26. M. Patel, N. Acharya, and A. Pratap, "The Experimental Investigation of Kinetics of Glass Transition of ZBLAN Glass by using Differential Scanning Calorimetry," Indian Journal of Pure & Applied Physics (IJPAP) **61**, 15–18 (2023).

27. H. Ebendorff-Heidepriem, T.-C. Foo, R. C. Moore, et al., "Fluoride glass microstructured optical fiber with large mode area and mid-infrared transmission," Opt. Lett. **33**(23), 2861–2863 (2008).

28. I. E. Gunduz, M. S. McClain, P. Cattani, et al., "3D printing of extremely viscous materials using ultrasonic vibrations," Addit. Manuf. **22**, 98–103 (2018).