Tech­ni­cal Ceram­ics by GTS – High-Perfor­mance Mate­ri­als for Indus­try and Research

Frequently Asked Ques­tions about Tech­ni­cal Ceram­ics from GTS

What makes GTS Keramik stand out as a manu­fac­turer of tech­ni­cal ceram­ics?

GTS Keramik is one of the lead­ing manu­fac­tur­ers of tech­ni­cal and indus­trial ceram­ics in Germany – and a devel­op­ment part­ner at the same time. As a family-owned company based in Düssel­dorf, we develop customer-specific mate­r­ial formu­la­tions rather than simply supply­ing stan­dard grades. Our customers speak directly with the engi­neers devel­op­ing their solu­tion – with­out multi-level sales chan­nels. Over 100 research collab­o­ra­tions with Euro­pean insti­tutes support our mate­ri­als devel­op­ment with reli­able data.

Which ceramic mate­ri­als does GTS process?

GTS manu­fac­tures tech­ni­cal ceram­ics from aluminium oxide (Al₂O₃) in dense and porous grades, zirco­nium oxide (ZrO₂), quartz with and with­out sili­con nitride addi­tion, spinel, tialite (aluminium titanate) and chamotte. We offer a total of 16 docu­mented mate­r­ial grades whose chem­i­cal compo­si­tion can be veri­fied via openly acces­si­ble refer­ence analy­ses.

What is the differ­ence between dense and porous ceram­ics in melt­ing crucibles?

Dense ceram­ics (e. g. AL99‑G with >99,7 % aluminium oxide) prevent any inter­ac­tion between crucible and melt and are the right choice for high-purity melt­ing processes such as plat­inum melt­ing. Porous ceram­ics (e. g. KR-98-VG with >98 % corun­dum) offer higher ther­mal shock resis­tance and are suited to appli­ca­tions with rapid ther­mal cycling. Which grade is opti­mal for a given process depends on the melt mate­r­ial, the furnace atmos­phere and the load cycle – GTS provides indi­vid­ual consul­ta­tion on this.

For which metals does GTS offer induc­tion crucibles?

GTS devel­ops induc­tion crucibles for melt­ing precious metals (plat­inum, rhodium, silver), indus­trial metals (iron, copper, zinc, tin) and special­ity metals (gallium, lead). Every crucible is tailored to the specific metal, the furnace atmos­phere and the ther­mal load cycle. The chem­i­cal resis­tance of the vari­ous GTS mate­r­ial grades to specific metals is docu­mented in the refer­ence analy­ses and prod­uct data sheets.

Which ceramic is suit­able for induc­tion crucibles?

In induc­tive melt­ing, it is not the ceramic that is heated but the metal inside the crucible. The ceramic must allow the elec­tro­mag­netic field to pass through with mini­mal loss while simul­ta­ne­ously with­stand­ing the heat gener­ated. Quartz is partic­u­larly well suited for this purpose because it is elec­tro­mag­net­i­cally trans­par­ent and has a low ther­mal expan­sion coef­fi­cient. At 1.000 °C, quartz expands by approx­i­mately 0,5 %, whereas zirco­nium oxide expands by around 1 %. This greater expan­sion can cause ther­mal stresses and crack forma­tion in zirco­nium oxide. GTS manu­fac­tures induc­tion crucibles primar­ily from quartz ceramic (grades Q100, Q100‑M, Q95F) and advises on select­ing the appro­pri­ate grade for your specific melt­ing process.

At what temper­a­tures can tech­ni­cal ceram­ics be used?

The service temper­a­ture depends on the mate­r­ial, as ceram­ics are not a single mate­r­ial but a whole class of mate­ri­als with very differ­ent temper­a­ture limits. Tech­ni­cal ceram­ics as manu­fac­tured by GTS oper­ate in a signif­i­cantly higher range than house­hold ceram­ics. Aluminium oxide (e. g. AL99‑G, KR-98-VG) is designed for contin­u­ous temper­a­tures up to approx. 1.700 °C. Zirco­nium oxide (ZR‑G, ZR-95-VG) is also suit­able for high-temper­a­ture appli­ca­tions and addi­tion­ally offers partic­u­larly high mechan­i­cal load-bear­ing capac­ity. Quartz ceramic (Q100, Q95F) is used primar­ily in melt­ing tech­nol­ogy, where high ther­mal shock resis­tance is deci­sive. Often more impor­tant than the maxi­mum temper­a­ture is the ther­mal shock resis­tance, as well as the atmos­phere (air, vacuum, protec­tive gas) and the mechan­i­cal load. GTS provides a TWB data sheet on this topic and offers indi­vid­ual consul­ta­tion.

Which ceramic grade is suit­able for which appli­ca­tion?

The choice of the correct ceramic grade depends on the appli­ca­tion. For high-purity melt­ing processes such as plat­inum or rhodium melt­ing, dense aluminium oxide (AL99‑G, >99,7 % purity) is the right choice. For appli­ca­tions with frequent ther­mal cycling, porous corun­dum (KR-98-VG, >98 %) is the better option due to its higher ther­mal shock resis­tance. Quartz ceramic (Q100, Q95F) is the stan­dard for induc­tion crucibles in melt­ing tech­nol­ogy. Zirco­nium oxide (ZR‑G) is used when maxi­mum mechan­i­cal strength and chem­i­cal resis­tance are required, for exam­ple in medical tech­nol­ogy. All 16 mate­r­ial grades are docu­mented with openly acces­si­ble refer­ence analy­ses.

Which ceramic is suit­able for melt­ing metals?

The right ceramic for metal melt­ing always depends on the specific metal. Metals react differ­ently with ceram­ics during melt­ing, depend­ing on temper­a­ture, oxida­tion and chem­i­cal compo­si­tion. GTS devel­ops induc­tion crucibles specif­i­cally for melt­ing precious metals such as plat­inum, rhodium and silver, indus­trial metals such as iron, copper, zinc and tin, and special­ity metals such as gallium and lead. The chem­i­cal resis­tance of each GTS mate­r­ial grade to specific metals is docu­mented in the refer­ence analy­ses. The ceramic must always be matched to the specific metal to avoid reac­tions, cont­a­m­i­na­tion or damage to the crucible.

How many times can a melt­ing crucible be used?

A melt­ing crucible is a consum­able part whose service life depends on several factors: the mate­r­ial of the crucible, the melt­ing temper­a­ture and the ther­mal cycle (heat­ing and cool­ing rate), the chem­i­cal aggres­sive­ness of the melt, and the mechan­i­cal load during handling. Heat­ing and cool­ing too rapidly signif­i­cantly short­ens service life, as ther­mal shock can lead to crack forma­tion. GTS opti­mises the mate­r­ial formu­la­tion specif­i­cally for your process in order to maximise service life. The recom­mended heat­ing and cool­ing curves are provided in our TWB data sheet.

Which ceramic is suit­able for ashing?

The appro­pri­ate ceramic for ashing depends on the mate­r­ial to be ashed. The deci­sive factors are the form of the mate­r­ial (liquid, powder or solid) and the required ashing temper­a­ture. For labo­ra­tory ashing processes, GTS offers crucibles in vari­ous mate­r­ial grades. Quartz crucibles (A1, A2, A3) are suit­able for stan­dard ashing at moder­ate temper­a­tures. For higher temper­a­tures or chem­i­cally more demand­ing samples, aluminium oxide crucibles (AL95‑G, AL99‑G) are the right choice. The selec­tion must always be adapted to the form of the mate­r­ial and the required temper­a­ture to avoid reac­tions, damage or mate­r­ial losses.

How wear-resis­tant is tech­ni­cal ceramic?

The wear resis­tance of ceram­ics depends strongly on the mate­r­ial and its microstruc­ture. Zirco­nium oxide (ZR‑G) offers the high­est frac­ture tough­ness and flex­ural strength, while aluminium oxide (AL99‑G, KR-98-VG) excels in hard­ness and chem­i­cal resis­tance. Another deci­sive factor is density: porous ceram­ics are less wear-resis­tant because they are more suscep­ti­ble to attack. Dense, finely sintered ceram­ics are signif­i­cantly more resis­tant and with­stand both mechan­i­cal and ther­mal loads for longer. GTS specialises in wear engi­neer­ing and manu­fac­tures highly wear-resis­tant ceramic compo­nents as one-off parts or in large-scale series produc­tion.

Can GTS also manu­fac­ture proto­types and one-off parts?

Yes. GTS manu­fac­tures ceramic compo­nents rang­ing from indi­vid­ual items to large-scale series. For proto­type produc­tion we also use 3D processes. After sinter­ing, the compo­nents become so hard that they can only be machined with diamond tools. The tran­si­tion from proto­type to stable series produc­tion is one of our core compe­tences – we support this process iter­a­tively through to repro­ducible qual­ity.

In which indus­tries are GTS prod­ucts used?

GTS supplies customers in melt­ing tech­nol­ogy and the foundry indus­try, crys­tal grow­ing, labo­ra­tory and medical tech­nol­ogy, aero­space, solar and battery tech­nol­ogy, the jewellery indus­try, and the lamp and glass indus­try. We also develop engi­neer­ing ceram­ics for mechan­i­cal engi­neer­ing and elec­tron­ics. Refer­ence customers include Bosch, Schott, Arcelor­Mit­tal and Yoko­gawa as well as numer­ous Euro­pean research insti­tutes.

What heat­ing and cool­ing curves does GTS recom­mend for dense ceram­ics?

Dense ceramic compo­nents should be heated and cooled in a controlled, uniform manner to avoid ther­mal shock. GTS provides a TWB data sheet (ther­mal shock resis­tance) contain­ing general recom­men­da­tions for heat­ing and cool­ing curves. Our engi­neers provide indi­vid­ual consul­ta­tion for specific appli­ca­tions.

Does GTS also offer ceram­ics for medical tech­nol­ogy?

Yes. In the field of phar­macy and medical tech­nol­ogy, GTS is recog­nised as an impor­tant supplier of high-qual­ity ceramic compo­nents. The company played a key role in the devel­op­ment of arti­fi­cial bone substi­tute mate­r­ial (TiFoam research project at the Fraun­hofer Insti­tute Dres­den). Due to its high mechan­i­cal load-bear­ing capac­ity and biocom­pat­i­bil­ity, zirco­nium oxide is partic­u­larly well suited to appli­ca­tions in implant tech­nol­ogy.