Synergetic Effect of ZnO with Different Dopents on Sintering By Wazo KOMATSU, Yusuke MORIYOSHI, and Naoto SETO (Faculty of Engineering, Tokyo Institute of Technology) The sinterability of Li doped and In doped zinc oxide and the mixtures of doped zinc oxides has been studied by measuring the isothermal shrinkage of compacts and the surface area change in the temperature range of 600 to 1200 Ž in air.
5348 Yogyo-Kyokai-Shi 77 [10] 1969 W. KOMATSU et al. 32 The dopent, Li2O, was found to promote the sintering of zinc oxide and In2O3 to inhibit. The result is explained by the diffusional transfer of interstitial zinc ions which have been controlled by the dopents. On the free sintering, powder mixtures of Li doped and In doped zinc oxide were found to have the greatest sinterability among pure, Li doped, In doped zinc oxides, and the mixtures. This result is explained by considering the electrostatic field caused by an electron rearrangement between In doped zinc oxide with higher Fermi level and Li doped zinc oxide with lower Fermi level. This electrostatic field between two oxides is thought to make good contact between particles and to enhance the sinterability of the mixtures of doped zinc oxides. On the sintering of compacts, however, no enhancement of the sinterability of the mixtures was observed. This unexpected result may be explained by assuming that the electrostatic force between the particles with different dopents is weaker than the compac ting force of tablets. [Received May 19, 1969] Fig. 1 Energy level diagram proposed for zinc oxide. Fig. 2 Schematic representation of energy levels of pure, lithium doped, and indium do ped zinc oxide.
Fig. 3 Schematic model of contact between lithium doped and indium doped zinc oxide. Fig. 4 Apparatus for measuring conductivity.
350 Yogyo-Kyokai-Shi 71 [10] 1969 W. KOMATSU et al. 34 Fig. 6 Linear plots of shrinkage (%) for sintering of pure and doped zinc oxides. Fig. 5 Conductivity of pure and doped zinc oxides as a function of temperature. Table 1 Apparent energy of activation and frequency factor for conductivity of pure and doped zinc oxides. Fig. 7 Linear plots of shrinkage (%) for sintering of mixtures of doped zinc oxides.
Table 2 Apparent energy of activation and frequency factor for sintering of pure, doped zinc oxides, and mix tures of doped zinc oxides. Fig. 8 Arrhenius plots for sintering of pure, doped zinc oxides, and mixtures of doped zinc oxides. Before sintering After sintering Fig. 9 Schematic representation of compact of mixtures of doped zinc oxides before and and after sintering. Fig. 10 Arrhenius plots for sintering of pure, doped zinc oxides, and mixtures of doped zinc oxides.
352 Yogyo-Kyokai-Shi 71 [10] 1969 W. KOMATSU et al. 36 Fig. 12 Relation between surface area and time for sintering of pure, doped zinc oxides, and mixtures of doped zinc oxides. Fig. 11 Relation between change in surface area and degas time. Fig. 13 Arrhenius plots for sintering of pure, doped zinc oxides, and mixtures of doped zinc oxides.
Table 3 Apparent energy of activation and frequency factor for sintering of pure, doped zinc oxi des, and mixtures of doped zinc oxides. 1) W.A.. Weyl, Ceram. Age 60, 28 (1952). 2) TI. Gray, J. Am. Ceram. Soc. 31, 534 (1954). 3) V.J. Lee and G. Parravano, J. Appl. Phys. 30, 1735 (1959). 4) J.P. Roberts, J. Hutihings and C. Wheeler, Trans. Brit. Ceram. Soc. 55, 75 (1953). 6) H.H.v. Baumbach and C. Wagner, Z. Phys. Chem. B 23, 199 (1933); K. Hauffe and J. Block, Z. Phys. Chem. 196, 438 (1950). 7) K. Hauffe, Angew. Chem. 72, 730 (1960). 8) K. Hauffe, "Reaktionen in und an Festen Stoffen", Springer.Verlag Berlin S. 202 (1966). 9) E.A. Seco and W.J. Moore, J. Chem. Phys. 26, 942 (1962).