Properties of Bi₄Ti₃O₁₂–(Na_1/2Bi_1/2)TiO₃Piezoelectric Ceramics

Abstract

Analysis of 24 h oesophageal pH studies can be problematic with many patients asymptomatic during the investigation, despite observations of reflux. The aim of this study was to carry out a cluster analysis of ambulatory pH studies to determine any underlying patterns and classes within the data. The results of 900 24 h pH studies were investigated using the Kohonen self-organizing feature map (SOFM), a neural network that can be used to identify clusters within multidimensional data. The clinical features were presented to the network and the main classes identified. The SOFM-based analysis showed that patients clinically assessed as having symptomatic reflux during the study could be described by four major classifications. The results also showed that the probability of identifying a correlation between symptoms and reflux during an investigation varies from 0.49 to 0.78 for the classes identified. The developed network may be a useful tool in the classification of pH data. The cluster-based technique may offer an alternative to standard statistical techniques for high-dimensional gastrointestinal data and form the basis of an expert system for the automated analysis of pH data.

Dielectric and piezoelectric properties of Na0.5Bi4.5Ti4O15–(x−1)Na0.5Bi0.5TiO3 composite ceramics

“…The piezoelectric constant d33 was directly measured by using a YE2730A d33 meter, and electromechanical coupling factors were measured by means of a resonance-antiresonance method. [15,16]. However, according to our XRD results, the bismuth layer-structured Na 0.5 Bi 4.5 Ti 4 O 15 phase can exist up to x = 99.…”

“…Many BLSF with m = 4 or 5 can also be derived from Bi 4 [8][9][10][11][12][13][14]. Recently, structural investigations on the Bi 4 Ti 3 O 12 + xNa 0.5 Bi 0.5 TiO 3 system have revealed that the bismuth layer-structured Na 0.5 Bi 4.5 Ti 4 O 15 phase and the perovskite Na 0.5 Bi 0.5 TiO 3 phase are prone to reject each other in their solid solution [15,16]. However, little data on the * Corresponding author.…”

Piezoresponse force microscopy investigations of Aurivillius phase thin films

“…6 On increasing the number of perovskite layers ͑n͒, the microstructural, magnetic, and physical properties of the materials can be altered significantly. [7][8][9][10][11][12][13][14][15] Chemical doping of perovskite type materials, without producing a large decrease in their Curie temperature ͑T c ͒, has been useful in enhancing their electrical and magnetic properties. 9,[16][17][18][19][20] Mn 3+ doping has been reported to be effective for suppressing leakage current and improving the polarization switching properties of Bi 4 Ti 3 O 12 single crystals.…”

Anisotropic properties and crystal structure of ferroelectric Na0.5Bi4.5Ti4O15

“…The crystal structure of chemical formula Na 0.5 Bi 4.5 Ti 4 O 15 can be expressed as one perovskite block Na 0.5 Bi 0.5 TiO 3 (NBT) inserted hypothetically between two bismuth layers of BT. With three pseudo-perovskite blocks Bi 2/3 1/3 TiO 3 (B T, where denotes cation vacancy) of BT [18], two types of pseudo-perovskite blocks are formed in NBT4 lattice. With the proposed mechanism of layer-by-layer intercalation by defects sweeping across grain [8], the transformation from BT to NBT4 has been verified by at the temperature exceeding 800 • C. A complex sequence of phase transitions of two type perovskite blocks may be traced in Fig.…”