• Basavaraj Angadi

      Articles written in Bulletin of Materials Science

    • Synthesis and thermal expansion hysteresis of Ca1–𝑥Sr𝑥Zr4P6O24

      Basavaraj Angadi V M Jali M T Lagare N S Kini A M Umarji

      More Details Abstract Fulltext PDF

      The low thermal expansion ceramic system, Ca1-𝑥Sr𝑥Zr4P6O24, for the compositions with 𝑥 = 0, 0.25, 0.50, 0.75 and 1 was synthesized by solid-state reaction. The sintering characteristics were ascertained by bulk density measurements. The fracture surface microstructure examined by scanning electron microscopy showed the average grain size of 2.47 𝜇m for all the compositions. The thermal expansion data for these ceramic systems over the temperature range 25–800°C is reported. The sinterability of various solid solutions and the hysteresis in dilatometric behaviour are shown to be related to the crystallographic thermal expansion anisotropy. A steady increase in the amount of porosity and critical grain size with increase in 𝑥 is suggested to explain the observed decrease in the hysteresis.

    • Synthesis, microstructure and thermal expansion studies on Ca0.5+𝑥/2Sr0.5+𝑥/2Zr4P6−2𝑥Si2𝑥O24 system prepared by co-precipitation method

      Basavaraj Angadi M R Ajith A M Umarji

      More Details Abstract Fulltext PDF

      We report on the synthesis, microstructure and thermal expansion studies on Ca0.5+𝑥/2Sr0.5+𝑥/2Zr4P6−2𝑥Si2𝑥O24 (𝑥 = 0.00 to 1.00) system which belongs to NZP family of low thermal expansion ceramics. The ceramics synthesized by co-precipitation method at lower calcination and the sintering temperatures were in pure NZP phase up to 𝑥 = 0.37. For 𝑥 ≥ 0.5, in addition to NZP phase, ZrSiO4 and Ca2P2O7 form as secondary phases after sintering. The bulk thermal expansion behaviour of the members of this system was studied from 30 to 850 °C. The thermal expansion coefficient increases from a negative value to a positive value with the silicon substitution in place of phosphorous and a near zero thermal expansion was observed at 𝑥 = 0.75. The amount of hysteresis between heating and cooling curves increases progressively from 𝑥 = 0.00 to 0.37 and then decreases for 𝑥 ≥ 0.37. The results were analysed on the basis of formation of the silicon based glassy phase and increase in thermal expansion anisotropy with silicon substitution.

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