Light scattering in glass-ceramics

Some demanding optical applications requirements can be met by transparent glass-ceramics. All glass-ceramics have inhomogeneous structure since they contain crystals distributed in glass. This inhomogeneity causes light scattering. In glass-ceramics for transparent optical elements, scattering needs to be reduced to a minimum. However, for diffuse reflection standards, light scattering is the determining property.

Previously, it was stated ^{Reference Beall and Duke6–Reference Berthier, Fokin and Zanotto8} that the scattering coefficient (turbidity) of glass-ceramics varies in a wide interval of wavelengths λ (e.g., in the range of visible light) according to the power law λ^−p , where (−p) is the exponent of constant value, and p ≤ 4. If the crystals are randomly distributed in the glass and are much smaller than the wavelength, then p = 4 (Rayleigh scattering).

Our studies ^{Reference Shepilov, Dymshits, Golubkov and Zhilin9,Reference Alekseeva, Dymshits, Zhilin, Zapalova, Shepilov, Golubkov, Kalmykov and Myacoedov10} as well as analysis of published data ^{Reference Zhu, Ma, Calvez, Zhang, Lucas, Adam, Shang and Rouxel11,Reference Chavoutier, Caurant, Majérus, Boulesteix, Loiseau and Jousseaume12} show that glass-ceramics frequently demonstrate “anomalous light scattering” ^{Reference Andreev13} with p > 4 (up to 9). This effect is a result of interference of light scattered by different crystals demonstrating short-range ordering in their mutual arrangement. ^{Reference Shepilov14} Interference can reduce light scattering by several times or more. ^{Reference Andreev13,Reference Shepilov14} This is demonstrated for Na₂O-Nb₂O₅-SiO₂ glass crystallization by the optical studies data ( Figure 1 ) supplemented by x-ray diffraction data for NaNbO₃ nanocrystals. ^{Reference Shepilov, Dymshits, Golubkov and Zhilin9} At the early stage of heat treatment (time t = 2, 4, and 6 h), scattering is close to Rayleigh scattering (p ≅ 4.5–4.8, see inset in Figure 1). At this stage, turbidity increases with the number of NaNbO₃ nanocrystals per unit volume according to x-ray diffraction data. As the number of nanocrystals further increases during longer heat treatments (t > 6 h), when their volume fraction becomes greater than ≈0.2 and increases up to ≈0.3, interference suppresses scattering, yielding p ≅ 6.2 and reducing turbidity.

Figure 1.

Turbidity α at three wavelengths λ (500, 550, and 600 nm) in the course of the crystallization of Na₂O-Nb₂O₅-SiO₂ glass as a function of heat-treatment time, t. At the early stage of crystallization (t ≤ 6 h, volume fraction of NaNbO₃ nanocrystals is less than 0.2), turbidity increases with increasing number of independent scatterers (nanocrystals) per unit volume. As the number of nanocrystals further increases (at t > 6 h, volume fraction becomes greater than 0.2 and increases up to ≈0.3), interference leads to a decrease in turbidity. At a given heat-treatment time, t, the wavelength dependence of the turbidity is described by the power law λ^−p and characterized by the magnitude of p. The inset shows values of p for different heat-treatment times. At the early stage (t ≤ 6 h), p ≅ 4.5–4.8, close to the Rayleigh value of 4 that is characteristic of small independent scatterers (nanocrystals). At t > 6, interference leads to p ≅ 6.2 (anomalous scattering). ^{Reference Shepilov, Dymshits, Golubkov and Zhilin9}

The greater the dispersion of scattering properties of crystals in glass-ceramics, the lower the interference and greater the scattering. ^{Reference Shepilov15} Based on this approach, glass-ceramics for laser components and standards of whiteness with high diffuse reflectance have been developed. ^{Reference Bortkevich, Varshavchik, Dymshits, Zhilin, Leykin, Polushkin, Seredenko, Chuvaeva and Shashkin16}

Systems for transparent glass-ceramics

Transparent glass-ceramics have been fabricated from many systems thus far and depending on the system, can be used for various applications. For example, glass-ceramics can be based upon “stuffed” β-quartz solid-solution structures with network replacement of Si⁴⁺ by Al³⁺ accompanied by filling of interstitial vacancies by Li⁺, Mg²⁺, and Zn²⁺ cations to preserve electrical neutrality ^{Reference Höland and Beall17} —in the Li₂O-MgO-ZnO-Al₂O₃-SiO₂ system with titania and/or zirconia as nucleators; ^{Reference Beall and Duke6,Reference Beall and Pinckney7,Reference Höland and Beall17,Reference Bach and Krause18} spinels in the (Li, Na, K, Mg, Zn)O-(Al, Ga)₂O₃-(Si, Ge)O₂ system ^{Reference Qiu3,Reference Beall and Duke6,Reference Beall and Pinckney7,Reference Höland and Beall17,Reference Chenu, Véron, Genevois, Matzen, Cardinal, Etienne, Massiot and Allix19,Reference Zhuang, Ueda and Tanabe20} with or without nucleators; mullite in the Al₂O₃-SiO₂ system ^{Reference Beall and Duke6,Reference Höland and Beall17} with BaO, K₂O, or Cs₂O additions; forsterite in the K₂O-MgO-Al₂O₃-SiO₂ system nucleated by TiO₂; ^{Reference Höland and Beall17} on ZnO or β-willemite in the K₂O-ZnO-Al₂O₃-SiO₂ system; ^{Reference Pinckney21} and mixed orthosilicates, Mg₂SiO₄-Zn₂SiO₄-Li₄SiO₄, in the K₂O-Li₂O-MgO-ZnO-Al₂O₃-SiO₂ system. ^{Reference Höland and Beall17} The distinct feature of these transparent glass-ceramics is that transition-metal (TM) ions (Cr³⁺, Cr⁴⁺, Ni²⁺, Co²⁺, V⁴⁺, Mn²⁺) can enter their crystalline phases, thus producing materials that can be used in broadband optical amplification, in tunable and IR lasers, in solar collectors, and as phosphors for solid-state lighting.

There are glass-ceramics based on fluoride crystals in oxyfluoride systems, ^{Reference Wang and Ohwaki22–Reference Qiu, Jiao, Zhou and Yang25} upon fresnoite-type crystals in the BaO-TiO₂-(Si,Ge)O₂ system, ^{Reference Komatsu2,Reference Komatsu and Honma26} upon various niobium-containing phases in the (Li, Na, K)₂O-Nb₂O₅-(Ge, Si, Te)O₂ ^{Reference Komatsu2,Reference Shepilov, Dymshits, Golubkov and Zhilin9,Reference Komatsu and Honma26–Reference Jain28} system, upon yttrium aluminum garnet in the Y₂O₃-Al₂O₃-SiO₂-Li₂O-TiO₂-ZrO₂ system, ^{Reference Fujita and Tanabe29} upon halogenides in the fluorozirconate ^{Reference Edgar, Spaeth, Schweizer, Assmann, Newman and MacFarlane30} system, and upon chalcogenides. ^{Reference Calvez, Adam and Zhang31} In these transparent glass-ceramics, rare-earth (RE) ions enter the crystalline phase, allowing for their use in solid-state lasers, fiber amplifiers, solid-state lighting, and color displays. There are several excellent reviews ^{Reference Komatsu2,Reference Qiu3,Reference Berthier, Fokin and Zanotto8,Reference de Pablos-Martín, Duran and Pascual23–Reference Komatsu and Honma26,Reference Jain28,Reference Fujita and Tanabe29,Reference Calvez, Adam and Zhang31–Reference Rüssel, Bocker, Stoica, Thieme and Keshavarzi35} devoted mainly to these transparent glass-ceramics that will not be discussed here.

Low-expansion glass-ceramics

Glass-ceramics based upon lithium aluminosilicate crystals with the β-quartz solid-solution structure in the Li₂O-Al₂O₃-SiO₂ (LAS) system that combine high transparency, near-zero coefficient of thermal expansion (CTE), excellent optical polishability, and strength ^{Reference Beall and Duke6,Reference Höland and Beall17,Reference Bach and Krause18} are used in the most important precision optical applications for telescope mirrors, laser gyroscopes, and optical parts. In addition, low-CTE, near-IR transparent LAS glass-ceramics form the foundation for glass-ceramic cooktop panels. In all of these transparent glass-ceramics, the substitution of (SiO₄) units in the β-quartz structure by (AlO₄) ones is achieved with charge compensation by Li⁺, Mg²⁺, Zn²⁺, or by AlPO₄. ^{Reference Höland and Beall17,Reference Bach and Krause18}

It was demonstrated by in situ high-temperature x-ray diffraction analysis ^{Reference Artukh, Astakhova, Zhilin, Filatov and Chuvaeva36} that in glass-ceramics with SiO₂ content ranging from 44–70 mol%, the CTE of disordered β-quartz solid-solution nanocrystals is near zero or slightly negative. The residual glass is highly siliceous with small TiO₂ and Al₂O₃ content, and its CTE is close to zero. The CTE of transparent glass-ceramics with high crystallinity fraction is thus determined to a large extent by the CTE value of the crystalline phase. ^{Reference Beall and Duke6,Reference Artukh, Astakhova, Zhilin, Filatov and Chuvaeva36} The precise tailoring of the glass composition and crystallization schedule allows for adjustment of CTE values to zero. ^{Reference Bach and Krause18}

Thermal shock-resistant color filters

Attracted by excellent transparency and low CTE values of glass-ceramics in the LAS system, we have developed violet, blue, green, red, purple, and neutral thermal shock-resistant color filters for laser systems and high-power light sources that can operate in high-temperature gradient fields, for instance, as aircraft signal lamps. ^{Reference Alekseeva, Dymshits, Tsenter, Zhilin, Golubkov, Denisov, Skoptsov, Malyarevich and Yumashev37} Spinel nanocrystals precipitate in these materials in a narrow “low-temperature” range of 720–770°C. TM ions enter their structure, while prolonged heat treatments lead to crystallization of β-quartz solid solution without decomposition of spinel crystals, resulting in transparent glass-ceramics with low CTE and unusual coloration. At elevated temperatures of 780–900°C that prevent spinel crystallization, TM ions entering the β-quartz solid solution produced differently colored thermal shock-resistant transparent glass-ceramics. Different tints can be obtained in the transparent glass-ceramics with the same composition by varying the heat-treatment temperature (e.g., Ni²⁺ ions in spinel nanocrystals produce green, and in β-quartz solid solution, the ions produce purple and red coloration ^{Reference Dymshits, Zhilin, Chuvaeva and Shepilov38} [ Figure 2 ]).

Figure 2.

(a) Images of green and red aircraft navigation lights made of Ni-doped Li₂O-Al₂O₃-SiO₂ transparent glass-ceramic; color coordinates in the Commission Internationale de l’Eclairage (CIE) chromaticity diagram, an international standard for primary colors that allows all other colors to be defined as a weighted sum of the three primary colors, and x-ray diffraction patterns of (b) the initial glass and transparent glass-ceramic, which is (c) green due to Ni²⁺ absorption in spinel nanocrystals and (d) red due to Ni²⁺ absorption in nanocrystals of β-quartz solid solution. ^{Reference Alekseeva, Dymshits, Tsenter, Zhilin, Golubkov, Denisov, Skoptsov, Malyarevich and Yumashev37,Reference Dymshits, Zhilin, Chuvaeva and Shepilov38} The blue numbers on the main plot represent wavelengths. When the initial brown-colored amorphous glass, whose x-ray pattern is presented in (b) and whose color coordinates are shown, is heat-treated at 720–770°C, (c) it transforms into a thermal shock-resistant green-colored glass-ceramic containing nanocrystals of Ni²⁺-doped spinel and β-quartz solid solution. (b) The position of the green signal lamp image on the CIE chromaticity diagram shows the color coordinates of green glass-ceramics. (d) When prepared by heat treatments at elevated temperatures of 780–900°C, red-colored transparent glass-ceramics contain nanocrystals of Ni²⁺-doped β-quartz solid solution. (b) The position of the red signal lamp image on the CIE chromaticity diagram shows the color coordinates of red glass-ceramics. Note: ss, solid solution; x, y, chromaticity coordinates; 2θ, diffraction angle.

Transparent glass-ceramics for broadband amplifiers and tunable lasers

The limited bandwidth of RE ion-doped amplifiers caused by narrow luminescent bandwidths of their 4f–4f optical transitions is a problem of communication technology. TM ions such as Ni²⁺ in octahedral coordination exhibit broadband near-IR emission with high quantum efficiency in crystals, yet there is no luminescence in Ni-doped glasses. Therefore, development of glass-ceramics suitable for fiber drawing with crystalline phases containing Ni²⁺ ions in octahedral position could solve this problem. Pinckney and Beall ^{Reference Höland and Beall17} demonstrated that transparent glass-ceramics based upon various spinels show wide-IR luminescence when doped with Ni²⁺ ions located in octahedral positions.

Further investigations by many research groups developed novel transparent glass-ceramics based on spinels and other crystals wherein Ni²⁺ ions located in octahedral sites and evaluated their spectral properties. Studies ^{Reference Qiu3,Reference Loiko, Dymshits, Zhilin, Alekseeva and Yumashev39} showed that one can control the strength of the local ligand field and the local symmetry around ^[VI]Ni²⁺ ions by precise tailoring of the transparent glass-ceramic composition, the nature and content of nucleating agents, the NiO concentration, and heat-treatment conditions. Some transparent glass-ceramics were developed containing a single crystalline phase with different octahedral sites. Other transparent glass-ceramics contain a combination of different crystalline phases where Ni²⁺ ions act as a single emission species in multiple octahedral local environments, ^{Reference Qiu3} which leads to broadening of the IR luminescent band. Energy transfer from Cr³⁺ ions to Ni²⁺ in spinel and from Yb³⁺ ions in glass to Ni²⁺ ions in spinel was achieved, increasing the luminescence intensity, while additions of Er³⁺and Bi ions resulted in a broad-IR luminescence provided by independent active ions without energy transfer. ^{Reference Qiu3} Broadband optical amplification in β-Ga₂O₃:Ni²⁺-based transparent glass-ceramics was demonstrated. ^{Reference Qiu3}

Transparent glass-ceramics for passive Q-switching of Er-lasers

“Eye-safe” Er lasers with emission wavelengths approximately 1.5–1.7 µm are used for applications that involve human contact with laser radiation and require short (nanosecond long) high peak power pulses that can be produced via passive Q-switching, a method for obtaining such pulses by modulating the intracavity losses by a saturable absorber (SA) inserted into the laser cavity. In SAs, absorption decreases with increasing fluence of the incident radiation. Materials for SAs need to have an absorption band that matches the laser emission wavelength, provide low saturation fluence and low nonsaturable losses, fast recovery time of the initial absorption, and high laser damage threshold. SAs based on Co²⁺:MgAl₂O₄ spinel single crystals were acknowledged as the best for Er, Yb:glass lasers with an emission wavelength of ∼1.54 µm. In these crystals, Co²⁺ ions with 3d ^{Reference Beall and Pinckney7} electronic configuration are predominantly located in tetrahedral sites, and their broadband IR absorption perfectly matches the ∼1.54 µm Er emission wavelength. Boiko et al. ^{Reference Boiko, Okhrimchuk, Shestakov, Bosenberg and Fejer40} were the first to introduce Co²⁺-doped transparent glass-ceramics based on spinel-type gahnite (ZnAl₂O₄) crystals as SAs. Following this, transparent glass-ceramics based on Co²⁺-doped spinel MgAl₂O₄ nano-sized crystals were introduced. ^{Reference Malyarevich, Denisov, Volk, Yumashev, Dymshits and Zhilin41,Reference Volk, Malyarevich, Yumashev, Dymshits, Shashkin and Zhilin42} A comparison with Co²⁺:MgAl₂O₄ single crystals demonstrated that glass-ceramics based on Co-doped MgAl₂O₄ spinel nanocrystals are good competitors to corresponding single crystals. ^{Reference Volk, Malyarevich, Yumashev, Dymshits, Shashkin and Zhilin42} Based on these encouraging results, transparent glass-ceramics for SAs with ^IVCo²⁺-doped nano-sized crystals of different spinels ^{Reference Alekseeva, Dymshits, Tsenter, Zhilin, Golubkov, Denisov, Skoptsov, Malyarevich and Yumashev37,Reference Boiko, Okhrimchuk, Shestakov, Bosenberg and Fejer40,Reference Malyarevich, Denisov, Volk, Yumashev, Dymshits and Zhilin41} were developed in ZnO-Al₂O₃-SiO₂ (ZAS), MgO-Al₂O₃-SiO₂ (MAS), and LAS systems. Other transparent glass-ceramics for SAs were also suggested. ^{Reference Yu, Chen, Feng, He, Wang and Hu43}

Motivated by the recent progress in directly pumped Er crystal lasers that provide oscillations at 1.6–1.7 µm, a new series of SAs based on transparent glass-ceramics were developed whose distinct feature is a shift of the absorption band of ^IVCo²⁺ ions to longer wavelengths due to the lower ligand field strength around Co²⁺ ions as compared to that in MgAl₂O₄ spinel ( Table I ). ^{Reference Loiko, Dymshits, Vitkin, Skoptsov, Zhilin, Shemchuk, Tsenter, Bogdanov, Malyarevich, Glazunov, Mateos and Yumashev44}

Table I.

Saturation intensity F _S (at ∼1.54 μm), recovery time τ, and long-wavelength edge of the infrared (⁴A₂(⁴F)→⁴T₁(⁴F)) absorption band of ^IVCo²⁺ ions, λ_th, for several Co²⁺-doped materials. ^{Reference Loiko, Dymshits, Vitkin, Skoptsov, Zhilin, Shemchuk, Tsenter, Bogdanov, Malyarevich, Glazunov, Mateos and Yumashev44}

Note: TGC, transparent glass-ceramic.

Glass-ceramics with RE ions embedded into crystalline phases have been studied in the search for efficient photoluminescent and up-conversion materials. An attractive idea to introduce RE ions into LAS glass-ceramics was not realized because β-quartz solid solution is a poor host for fluorescent cations. ^{Reference Höland and Beall17,Reference Qiu, Jiao, Zhou and Yang25} Recently, researchers were able to incorporate RE ions into the crystalline phases of aluminosilicate glass-ceramics, where these crystalline phases were not β-quartz solid solution, but RE titanates, titanites-zirconites, and niobates. ^{Reference Dymshits, Zhilin, Chuvaeva and Shepilov38,Reference Dymshits, Zhilin, Alekseeva, Skoptsov, Malyarevich and Yumashev45–Reference Loiko, Dymshits, Alekseeva, Zhilin, Tsenter, Vilejshikova, Bogdanov, Mateos and Yumashev49} Similar to RE fluorides, these nanocrystals ensure a low-phonon energy lattice surrounding the RE ions, but these glass-ceramics possess high thermomechanical properties and their compositions are highly reproducible.

Transparent glass-ceramics based on nano-sized crystals of RE titanates and titanates-zirconates

When LAS or MAS glasses nucleated by TiO₂ or ZrO₂ are doped with RE ions, RE₂(Ti, Zr)₂O₇ crystals with the defect-fluorite structure precipitate. ^{Reference Dymshits, Zhilin, Chuvaeva and Shepilov38,Reference Dymshits, Zhilin, Alekseeva, Skoptsov, Malyarevich and Yumashev45–Reference Dymshits, Loiko, Skoptsov, Malyarevich, Yumashev, Zhilin, Alekseeva, Tsenter and Bogdanov47} At elevated temperatures, a disordered and then ordered pyrochlore-type structure is formed.

When doped with Er³⁺ and Yb³⁺ ions, these transparent glass-ceramics demonstrate substantial enhancement (near 10×) of red up-conversion emission around ∼650 nm, ^{Reference Dymshits, Loiko, Skoptsov, Malyarevich, Yumashev, Zhilin, Alekseeva, Tsenter and Bogdanov47} which is important for phosphors and solid-state lightning. They are also candidates for a medium for effective laser generation in the spectral range of 1.5 μm. ^{Reference Dymshits, Zhilin, Chuvaeva and Shepilov38}

Transparent glass-ceramics based on nano-sized crystals of RE orthoniobates

Recently, transparent glass-ceramics with the RE niobate nanophase in the dual role of luminescent active crystal and nucleator of β-quartz solid solution in LAS glasses were prepared. ^{Reference Dymshits, Alekseeva, Zhilin, Tsenter, Loiko, Skoptsov, Malyarevich, Yumashev, Mateos and Baranov48,Reference Loiko, Dymshits, Alekseeva, Zhilin, Tsenter, Vilejshikova, Bogdanov, Mateos and Yumashev49} The optical properties of these glass-ceramics were directly linked to the structure of RE niobates, which changes from the defect fluorite to the tetragonal, and then, to the monoclinic form ( Figure 3 ). RENbO₄ nanocrystals provide promising spectral-luminescent properties while the large amount of β-quartz solid solution ensures high thermal shock resistance of the glass-ceramics. Transparent glass-ceramics with the tetragonal (Er, Yb)NbO₄ nanophase have potential for laser operation in the eye-safe region. ^{Reference Dymshits, Alekseeva, Zhilin, Tsenter, Loiko, Skoptsov, Malyarevich, Yumashev, Mateos and Baranov48} RENbO₄-based transparent glass-ceramics are interesting materials for double (RE³⁺, Yb³⁺) or triple (RE₁ ³⁺, RE²³⁺, Yb³⁺) codoping for color-tunable phosphors in the visible region, for generation of warm/cold white light. ^{Reference Loiko, Dymshits, Alekseeva, Zhilin, Tsenter, Vilejshikova, Bogdanov, Mateos and Yumashev49}

Figure 3.

(a) Image of polished sample (inset) and transmission electron microscope (TEM) image of lithium aluminosilicate glass doped with Er₂O₃, Yb₂O₃, and Nb₂O₅; (b) Image of polished sample (inset) and TEM image of lithium aluminosilicate glass-ceramics doped with Er₂O₃, Yb₂O₃, and Nb₂O₅ prepared at 1000°C for 6 h. ^{Reference Dymshits, Alekseeva, Zhilin, Tsenter, Loiko, Skoptsov, Malyarevich, Yumashev, Mateos and Baranov48} The value indicated in the figure denotes heat-treatment schedule. Both TEM images demonstrate nearly uniform distribution of inhomogeneous regions (dark regions) without any clustering. The sizes of the regions of inhomogeneity are approximately 10 nm in the initial glass and approximately 15 nm after the heat treatment. (c) Absorption spectra related to the ²F_7/2→²F_5/2 (Yb³⁺) transition for the initial glass and glass-ceramics containing (Er, Yb)NbO₄ nanocrystals. (d) Absorption spectra related to the ⁴I_15/2→⁴I_13/2 (Er³⁺) transition for the initial glass and glass-ceramics containing (Er, Yb)NbO₄ nanocrystals after the indicated heat-treatment schedules. (e) Near-infrared photoluminescence of Er³⁺ ions for the initial glass and glass-ceramics doped with Er₂O₃, Yb₂O₃, and Nb₂O₅ and prepared at 800, 900, and 1000°C for 6 h; the excitation wavelength is 960 nm. (f) X-ray diffraction patterns of the initial and heat-treated glasses doped with 3 mol% Yb₂O₃ and 3 mol% Nb₂O₅ at the indicated heat-treatment temperatures and duration. Patterns are shifted for ease of observation. The absorption and luminescent properties of these glass-ceramics are directly linked to the structure of rare-earth (RE) niobates, which change structure from the defect fluorite to tetragonal and then to monoclinic due to heat treatment. RE orthoniobates provide promising spectral-luminescent properties, while the crystallization of a large amount of β-quartz solid solution ensures near-zero coefficient of thermal expansion of these novel, transparent glass-ceramics. Note: 2θ, diffraction angle; PL, photoluminescence; T′, crystals with disordered fluorite-type structure; T, crystals with tetragonal structure; M, crystals with monoclinic structure; ss, solid solution. ^{Reference Dymshits, Alekseeva, Zhilin, Tsenter, Loiko, Skoptsov, Malyarevich, Yumashev, Mateos and Baranov48,Reference Loiko, Dymshits, Alekseeva, Zhilin, Tsenter, Vilejshikova, Bogdanov, Mateos and Yumashev49}

Summary

Detailed knowledge of the sequence of phase transformations in the course of glass-ceramic formation is required to find the balance between (a) maximizing the fraction of desired crystalline phase accommodating active ions; (b) minimizing the fractions of crystalline and amorphous phases accommodating active ions in coordinations different from that desired; and (c) minimizing scattering losses.

Based on this strategy, transparent glass-ceramics doped with Co²⁺ and Ni²⁺ ions for thermal shock-resistant color filters, for broadband near-IR optical amplifiers, and for passive Q-switching of eye-safe Er lasers as well as glass-ceramics with RE titanates, titanates-zirconates, and niobates in dual roles of nucleators and active crystals were developed. The selective partition of transition-metal ions into the crystals with spinel structure and of RE ions into titanate, titanate-zirconate, niobate, and fluoride crystals is an approach to the design of new multifunctional materials. In addition to traditional melt quenching and sinter crystallization, laser patterning and glass-ceramic melt-in-tube fiber drawing are fascinating methods for forming glass-ceramics that broaden the compositions and shaping of transparent glass-ceramics.