Canadian Patents & Development Ltd.

Her Majesty the Queen in Right of Canada, As Represented by the Minister

Mcmaster University

Her Majesty the Queen As Represented by the Minister of National Defence

Ontario Centre for Materials Research

Patrick S Nicholson

Kimihiro Yamashita

Michael Sayer

Fred F Lange

Michael F Bell

Narenora Patel

Aichun Tan

Alicja H Grzymer

Thomas Troczynski

Jan Van Den Andel

Chu K Kuo

Disclosed herein is a method of forming a single crystal film of sodium-beta'-alumina, comprising the steps of providing a single crystal substrate with one surface being arranged to minimize nucleation sites thereon, at least a portion of the substrate including alumina. A single crystal substrate is then deposited in a chamber, along with a precursor in the chamber. The precursor has a sufficient quantity of sodium species in a vapor phase and at an energy level sufficient to react with the alumina to form sodium-beta'-alumina. The precursor also includes a sufficient quantity of a stabilizing ion with a valence equal to or lower than aluminum to minimize decomposition of sodium-beta'-alumina to sodium-beta-alumina.

Method of forming a single crystal film of sodium-beta '-alumina

A surface-strengthened composite ceramic material has a ceramic matrix and a refractory phase dispersed at least in and close to the surface of the matrix. The refractory phase includes beta-alumina particles in which larger cations producing a larger molar volume replace sufficient smaller cations in beta-alumina particles in and close to the surface of the composite ceramic material to cause compressive surface stresses which increase the surface strength of the composite ceramic material. The smaller cations are replaced by the larger cations after firing of the composite ceramic material.

Surface strengthened composite ceramic material

A focussing element for use in a lenseless, focussed transducer for producing a semi-focussed, ultrasonic beam comprises a body formed of electrical insulating material and a plurality of piezoelectric elements disposed in one end of the body, each element being planar, extending outwardly from a common axis, and being disposed at a predetermined angel to the common axis whereby to define a common focal point on the axis, and electrical conductors secured to the piezoelectric element for electrically exciting the elements.

Method of making a focussing element for use in a lenseless focussed

A method of converting a feed solid polycrystalline of .beta. alumina into a hydronium conductor requires the preselection of an appropriate feed ceramic preferably with a chemical formula;

Method of converting a precursor ceramic solid into a solid ceramic

The spray-drying of a feed liquid mixture containing dissolved feed elements is used to produce precursor powders of Na.sup.+ -super conducting sodium gadolinium silicate (Na.sub.5 GdSi.sub.4 O.sub.12), (NGS), and sodium yttrium silicate (Na.sub.5 YSi.sub.4 O.sub.12), NYS. Using these powders, very dense (&gt;97% theoretical) solids are obtained on sintering. The resistivities of the NGS and NYS polycrystalline ceramics are 5 and 7 (.OMEGA. cm) respectively at 300.degree. C. and are dependent on the f(NGS) or f(NYS) values. In the case of NYS, the resistivity/f(NYS) relationship takes the form ##EQU1## indicative of resistive and conductive phases mixed more in parallel than in series.

Silicate superionic conductors and method of making same

An hydronium polycrystalline superionic conductor, having the formula (H.sub.3 O.sup.+,Na.sup.+).sub.5 (Re)Si.sub.4 O.sub.12, where Re=Y or Gd, is produced from precursor material being Na.sub.5 YSi.sub.4 O.sub.12 or Na.sub.5 GdSi.sub.4 O.sub.12. In order to accomplish the aforesaid a range of intermediate ceramics may be produced replacing part of the precursor ceramic sodium by ions of elements in 1A group of the Periodic Table that have an atomic weight above 32 and preferably ions of potassium, cesium, or mixtures of potassium and cesium. To produce the superionic hydronium polycrystalline ceramic conductor and the intermediate ceramic from the feed ceramics aforesaid, the feed ceramic is placed in a chloride melt wherein part of the sodium in the feed ceramic lattice is replaced by an appropriate cation from the melt such as potassium and cesium. Subsequently, a field assisted ionic exchange takes place to now replace the interceded potassium and cesium ions with the hydronium (H.sub.3 O.sup.+) ion, whereby the aforesaid hydronium, superionic, solid polycrystalline ceramic conductor is achieved.

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Ancaster, Canada

Patrick S Nicholson