Micro-Raman probing of short-range disorder in lanthanum-doped lead titanate films

✍ Scribed by P. S. Dobal; S. B. Majumder; S. Bhaskar; R. S. Katiyar

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 145 KB
• Volume: 30
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/(sici)1097-4555(199907)30:7<567::aid-jrs420>3.0.co;2-j

✦ Synopsis

Lanthanum-modified lead titanate thin films with composition Pb 1-x La x Ti 1-x /4 O 3 , where x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30, were grown on (0001) sapphire using the sol-gel process. Raman scattering, in the temperature range 75-783 K, was used to probe the phase transition and the possibility of relaxor behavior in these compositions. The x-ray diffraction measurements indicate a cubic structure for x > 0.15, while the Raman modes were observed up to x = 0.25. The phonon modes exist above the tetragonal-to-cubic phase transition temperature in these solid solutions owing to a short-range structural disorder in the paraelectric cubic phase. The lack of a well defined transition temperature suggested a diffuse nature of the ferroelectric phase transition. An increase in the diffuseness of transitions was evidenced with increasing La content, which indicates the relaxor behavior and also its relationship with the local disorder in these materials.