• PDF / 1,728,684 Bytes
• 10 Pages / 584.957 x 782.986 pts Page_size
• 54 Downloads / 202 Views

DOWNLOAD

REPORT

---

William J. Borland DuPont Electronic Technologies, Research Triangle Park, North Carolina 27707

Jon-Paul Maria Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (Received 24 July 2009; accepted 8 September 2009)

In situ residual gas analyzer techniques were used to identify process-property relationships that regulate microstructure evolution in chemical solution-deposited BaTiO3 films. In situ analysis of furnace exhaust gasses enabled quantitative exploration of thermolysis and crystallization reactions and an ability to identify processing parameters that influence the temperature ranges over which they occur. The atmospheric analysis was instrumental in identifying heat treatments that produced optimally consolidated precursor gels that crystallized into BaTiO3 layers with optimized structure and properties. Slow ramp rates resulted in higher porosity, larger grain size, and a dramatic drop in the capacitor yield. Fast ramp rates produced similar trends; however, the mechanisms were distinct. The effects of oxygen partial pressure were also explored. BaTiO3 grain size increased with increasing pO2, whereas there was no appreciable influence on density and capacitor yield. Optimal firing parameters, i.e., 20  C/min ramp rate at a pO2 of 10 13 atm, were identified as those that produced an overlap in the temperature ranges of thermolysis and crystallization reactions and thus a precursor gel with a density and compliance that supports crystallization and densification while tolerating the associated volume contraction. This in situ approach to analyze downstream furnace gas is shown to be a generically applicable means to understand synthesis methods that are complicated by simultaneous mechanisms of precursor decomposition, extraction of volatile components, and crystallization.

I. INTRODUCTION

Chemical solution deposition (CSD) of barium titanate is an attractive low-cost synthesis method suitable for large-scale production. CSD has many advantages including high purity, compositional homogeneity, straightforward variation of stoichiometry, and control over phase formation and microstructure development. Initial investigations of solution-based barium titanate processing were intended to decrease the processing temperatures and obtain fine-sized, high-purity powders.1-4 Analogous methods were first applied to synthesize barium titanate thin films by Yanovskaya et al.5 Since these pioneering reports, solution-based barium titanate powders and thin films have been prepared by using multiple precursor a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0066 J. Mater. Res., Vol. 25, No. 3, Mar 2010

http://journals.cambridge.org

Downloaded: 14 Mar 2015

chemistries. The most popular ones include sol-gel approaches with alkoxide solutions,6-9 metalorganic and oxalate salt decomposition,10-13 and hybrid routes using carboxylates and alkoxides.14-17 These studies revealed the importance of solution chemistry an