Thermal analyses of bulk amorphous oxides and silicates of zirconium and hafnium

S. V. Ushakov, C. E. Brown, A. Navrotsky, A. Demkov, C. Wang, B. Y. Nguyen

Research output: Contribution to journalConference articlepeer-review

8 Scopus citations

Abstract

Amorphous pure and Y-doped ZrO2 and HfO2 were prepared by precipitation with ammonia or hydrazine. Amorphous zirconium and hafnium silicates with SiO2 content from 10 to 90 mol % were prepared by sol-gel. Crystallization was studied by differential scanning calorimetry (DSC) at 20 °C/min and crystallite size after crystallization was determined from XRD data. ZrO2 crystallized into the tetragonal phase with ΔH -21 ±2 kJ/mol and HfO2 into the monoclinic phase with ΔH -31 ±2 kJ/mol. Doping with 20 at% Y decreased crystallite size after crystallization. Crystallization temperatures for pure and Y-doped ZrO2 samples were in the range 420-440 °C. Crystallization temperatures for pure and Y-doped HfO2 samples varied from 470 to 570°C and correlate with surface area. Crystallization onset temperature in silicates increased with silica content from about 650 to 950 °C for ZrO2·SiO2 and from 740 to 1030 °C for HfO2·SiO2. Tetragonal zirconia and hafnia were the only crystalline phases formed below 1100 °C in all zirconium silicates and in hafnium silicates with more than 10 mol% SiO2. Crystallite size after crystallization decreased with increase in silica content. In hafnium silicate, a decrease in HfO2 crystallite size from 5 to 2.5 ±1 nm corresponds to a crystallization enthalpy change from -22 to -15 ±2 kJ/mol. The tetragonal HfO2/amorphous SiO2 interface energy can be calculated from calorimetric data as -0.25 J/m2. The critical particle size for the tetragonal to monoclinic transformation of HfO2 in HfO2-SiO2 system is about 6 nm. We predict that tetragonal HfO2 will be stabilized in films thinner than 2 nm.

Original languageEnglish (US)
Pages (from-to)3-8
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
Volume745
DOIs
StatePublished - 2002
Externally publishedYes
EventNovel Materials and Processes for Advanced CMOS - Boston, MA, United States
Duration: Dec 2 2002Dec 4 2002

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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