Research Of The Low Tempreture Hingh Hardness Lead-free Transparent Frit Glaze

Senior porcelain has been deeply loved by people because of its goodappearance and fine intrinsic properties，such as bone china，steatite porcelainand quartz enriched porcelain．In the past，the lead fritted glaze was used asdecorative material of senior porcelain．But，it is harmful to human healthy，because the lead release from the glaze is occurred when it is used. Meanwhile,the hardness of the lead fritted glaze is lower．Although，low temperaturelead-free fritted glaze by twice sintering process have been developed at homeand abroad. But, the hardness of glaze is too low after porcelain sintering.Therefore，the preparation of high hardness lead-free fritted glaze in lowtemperature (1180℃) is an important research and development orientation．R2O-RO-Al2O3-B2O3-SiO2-ZrO2low temperature high hardness lead-freefritted glaze were prepared using zirconite substitution of a portion of SiO2in thesystem of R2O-RO-Al2O3-B2O3-SiO2fritted glaze. Potassium feldspar，Na2B4O710H2O，talc，H3BO3，Li2CO3，CaCO3，ZnO，BaCO3，SrCO3，Al2O3，La2O3， Al(OH)3，quartz，zirconite were used as starting materials．At thecondition of maintaining frit melting temperature and glaze firing temperature,the composition of the glaze was reasonably adjusted. The influences of thecontent B2O3, ZrO2and Li2O on sintering process， phase composition，microstructure and hardness of the glaze were investigated by TG-DSC，XRD，SEM and Vickers hardness tester．On this basis, the formula of glaze wasoptimized by orthogonal design experiment method. The optimal preparedprocess was found for the high hardness lead-free transparent fritted glaze fortwice sintering.In the experiments of zirconite used to substitute for a portion of SiO2, theinfluences of the content ZrO2on the properties of R2O-RO-Al2O3-SiO2-B2O3-ZrO2fritted glaze were studied． The results show that the glaze firingtemperature increase with the rise of the content ZrO2from0to5.39%in glaze.At the same glaze firing temperature condition, the hardness and crystallinity of the glaze first increase and then decrease with the rise of the content ZrO2. Whenthe glaze firing temperature is at1180℃and the ZrO2content is3.6%，thehardness of transparent glaze reach to6027MPa due to the reinforcement of thecolumnar zirconite crystallization with the length of1~10μm．In the experiments of B2O3introduced by Na2B4O710H2O and H3BO3, theinfluences of the B2O3content from8.01%to12.02%on R2O-RO-Al2O3-B2O3-SiO2-ZrO2fritted glaze were studied. The results show that the B2O3inhibitzirconite crystallization in R2O-RO-Al2O3-B2O3-SiO2-ZrO2fritted glaze. Withthe increase of the B2O3content, the ZrSiO4crystallization in fritted glazedecrease, and the crystal grain size of ZrSiO4decrease. Moreover, the inhibitionbecame stronger with increasing the B2O3content. However, the hardness ofglaze first increase and then decrease with the rise of the B2O3content. When theB2O3content is9.73%，the hardness of the fritted glaze reach up to the highest5898Mpa．So，the boron anomaly phenomenon has appeared in the influence ofthe B2O3content on hardness．Meanwhile, the linear expansion coefficient of thefritted glaze decrease from8.2×10-6/℃to6.8×10-6/℃with the increase of theB2O3content. Since the linear expansion of ceramic body is8.7×10-6/℃, thelinear expansion coefficient difference between the glaze and body can becontrolled within the limits of1~2×10-6/℃, which is beneficial to formation ofthe positive binding the glaze with body. The addition of B2O3enhancecombination of the glaze and body with the melting and diffusion impact. So, themiddle layers between glaze and body are formed, which make a strongcombination of glaze and body and enhance the adaptability of the glaze andbody．In the experiment of Li2O introduced by lithium carbonate, the influence ofthe Li2O content on the properties of R2O-RO-Al2O3-B2O3-SiO2-ZrO2frittedglaze were studied. The results show that the hardness and crystallinity of glazefirst increase and then decrease with the increase of the Li2O content from0to4.08%at the temperature of1180℃in the seven formula system. When Li2O is3.19%，Na2O is0.54%，K2O is3.67%，the glaze has optimal performance withthe hardness of6120MPa.Based on the single factor experiment of ZrO2，B2O3，Li2O influence onfritted glaze，the orthogonal tests with seven factors and three levels weredesigned．The influences of potassium feldspar，borax，boric acid，lithium carbonate， calcium carbonate， quartz， zirconite on the properties ofR2O-RO-Al2O3-B2O3-SiO2-ZrO2frit glaze were studied. The results show thatzirconite have the most effect on the hardness，transparency and gloss of frittedglaze, the influence followed by potassium feldspar， boric acid， lithiumcarbonate，calcium carbonate，quartz，borax．When the composition of glaze is4.25%Zirconite，22.93%potassium feldspar，15.3%boric acid，4.68%lithiumcarbonate，15.3%calcium carbonate，21.23%quartz，2.69%talc，5.95%ZnO，3.85%barium carbonate，2.57%strontium carbonate，0.85%alumigel，0.42%lanthana，the hardness of the fritted glaze with80transparency and108gloss is6631MPa.